BuSpar®
(buspirone HCl, USP)
BuSpar® (buspirone hydrochloride tablets, USP) is an antianxiety agent that is not chemically or pharmacologically related to the benzodiazepines, barbiturates, or other sedative/anxiolytic drugs.
Buspirone hydrochloride is a white crystalline, water soluble compound with a molecular weight of 422.0. Chemically, buspirone hydrochloride is 8-[4-[4-(2-pyrimidinyl)-1-piperazinyl]butyl]-8-azaspiro[4.5]decane-7,9-dione monohydrochloride. The empirical formula C21H31N5O2•HCl is represented by the following structural formula:
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BuSpar is supplied as tablets for oral administration containing 5 mg, 10 mg, 15 mg, or 30 mg of buspirone hydrochloride, USP (equivalent to 4.6 mg, 9.1 mg, 13.7 mg, and 27.4 mg of buspirone free base, respectively). The 5 mg and 10 mg tablets are scored so they can be bisected. Thus, the 5 mg tablet can also provide a 2.5 mg dose, and the 10 mg tablet can provide a 5 mg dose. The 15 mg and 30 mg tablets are provided in the DIVIDOSE® tablet design. These tablets are scored so they can be either bisected or trisected. Thus, a single 15 mg tablet can provide the following doses: 15 mg (entire tablet), 10 mg (two thirds of a tablet), 7.5 mg (one half of a tablet), or 5 mg (one third of a tablet). A single 30 mg tablet can provide the following doses: 30 mg (entire tablet), 20 mg (two thirds of a tablet), 15 mg (one half of a tablet), or 10 mg (one third of a tablet). BuSpar Tablets contain the following inactive ingredients: colloidal silicon dioxide, lactose, magnesium stearate, microcrystalline cellulose, and sodium starch glycolate. The 30 mg tablet also contains iron oxide.
Last updated on RxList: 7/6/2009
BuSpar is indicated for the management of anxiety disorders or the short-term relief of the symptoms of anxiety. Anxiety or tension associated with the stress of everyday life usually does not require treatment with an anxiolytic.
The efficacy of BuSpar has been demonstrated in controlled clinical trials of outpatients whose diagnosis roughly corresponds to Generalized Anxiety Disorder (GAD). Many of the patients enrolled in these studies also had coexisting depressive symptoms and BuSpar relieved anxiety in the presence of these coexisting depressive symptoms. The patients evaluated in these studies had experienced symptoms for periods of 1 month to over 1 year prior to the study, with an average symptom duration of 6 months. Generalized Anxiety Disorder (300.02) is described in the American Psychiatric Association's Diagnostic and Statistical Manual, III1 as follows:
Generalized, persistent anxiety (of at least 1 month continual duration), manifested by symptoms from three of the four following categories:
The above symptoms would not be due to another mental disorder, such as a depressive disorder or schizophrenia. However, mild depressive symptoms are common in GAD.
The effectiveness of BuSpar in long-term use, that is, for more than 3 to 4 weeks, has not been demonstrated in controlled trials. There is no body of evidence available that systematically addresses the appropriate duration of treatment for GAD. However, in a study of long-term use, 264 patients were treated with BuSpar for 1 year without ill effect. Therefore, the physician who elects to use BuSpar for extended periods should periodically reassess the usefulness of the drug for the individual patient.
The recommended initial dose is 15 mg daily (7.5 mg b.i.d.). To achieve an optimal therapeutic response, at intervals of 2 to 3 days the dosage may be increased 5 mg per day, as needed. The maximum daily dosage should not exceed 60 mg per day. In clinical trials allowing dose titration, divided doses of 20 mg to 30 mg per day were commonly employed.
The bioavailability of buspirone is increased when given with food as compared to the fasted state (see CLINICAL PHARMACOLOGY). Consequently, patients should take buspirone in a consistent manner with regard to the timing of dosing; either always with or always without food.
When buspirone is to be given with a potent inhibitor of CYP3A4, the dosage recommendations described in the PRECAUTIONS: DRUG INTERACTIONS section should be followed.
BuSpar® (buspirone hydrochloride tablets, USP) Tablets, 5 mg and 10 mg (white, ovoidrectangular with score, MJ logo, strength and the name BuSpar embossed) are available in bottles of 100.
5 mg tablets
NDC 0087-0818-41 Bottles of 100
10 mg tablets
NDC 0087-0819-41 Bottles of 100
Tablets, 15 mg white, in the DIVIDOSE® tablet design imprinted with the MJ logo, are available in bottles of 60 and 180. Tablets, 30 mg pink, in the DIVIDOSE® tablet design imprinted with the MJ logo, are available in bottles of 60. The 15 mg and 30 mg tablets are scored so that they can be either bisected or trisected. The 15 mg tablet has ID number 822 on one side and on the reverse side, the number 5 on each trisect segment. The 30 mg tablet has ID number 824 on one side and on the reverse side, the number 10 on each trisect segment.
15 mg tablets
NDC 0087-0822-32 Bottles of 60
NDC 0087-0822-33 Bottles of 180
30 mg tablets
NDC 0087-0824-81 Bottles of 60
US Patent No. 5,015,646
Store at 25°C (77°F); excursions permitted between 15°C to 30°C (59°F to 86°F) [see USP controlled room temperature]. Dispense in a tight, light-resistant container (USP).
REFERENCE
1. American Psychiatric Association, Ed.: Diagnostic and Statistical Manual of Mental Disorders—III, American Psychiatric Association, May 1980.
Bristol-Myers Squibb Company. Princeton, NJ 08543 USA. Revised March 2007.
Last updated on RxList: 7/6/2009
(See also PRECAUTIONS)
The more commonly observed untoward events associated with the use of BuSpar not seen at an equivalent incidence among placebo-treated patients include dizziness, nausea, headache, nervousness, lightheadedness, and excitement.
One guide to the relative clinical importance of adverse events associated with BuSpar is provided by the frequency with which they caused drug discontinuation during clinical testing. Approximately 10% of the 2200 anxious patients who participated in the BuSpar premarketing clinical efficacy trials in anxiety disorders lasting 3 to 4 weeks discontinued treatment due to an adverse event. The more common events causing discontinuation included: central nervous system disturbances (3.4%), primarily dizziness, insomnia, nervousness, drowsiness, and lightheaded feeling; gastrointestinal disturbances (1.2%), primarily nausea; and miscellaneous disturbances (1.1%), primarily headache and fatigue. In addition, 3.4% of patients had multiple complaints, none of which could be characterized as primary.
The table that follows enumerates adverse events that occurred at a frequency of 1% or more among BuSpar (buspirone hydrochloride) patients who participated in 4-week, controlled trials comparing BuSpar with placebo. The frequencies were obtained from pooled data for 17 trials. The prescriber should be aware that these figures cannot be used to predict the incidence of side effects in the course of usual medical practice where patient characteristics and other factors differ from those which prevailed in the clinical trials. Similarly, the cited frequencies cannot be compared with figures obtained from other clinical investigations involving different treatments, uses, and investigators. Comparison of the cited figures, however, does provide the prescribing physician with some basis for estimating the relative contribution of drug and nondrug factors to the side-effect incidence rate in the population studied.
TREATMENT-EMERGENT ADVERSE EXPERIENCE INCIDENCE IN PLACEBO-CONTROLLED
CLINICAL TRIALS*
| Adverse Experience | (Percent of Patients Reporting) | |
| BuSpar (n=477) |
Placebo (n=464) |
|
| Cardiovascular | ||
| Tachycardia/Palpitations | 1 | 1 |
| CNS | ||
| Dizziness | 12 | 3 |
| Drowsiness | 10 | 9 |
| Nervousness | 5 | 1 |
| Insomnia | 3 | 3 |
| Lightheadedness | 3 | — |
| Decreased Concentration | 2 | 2 |
| Excitement | 2 | — |
| Anger/Hostility | 2 | — |
| Confusion | 2 | — |
| Depression | 2 | 2 |
| EENT | ||
| Blurred Vision | 2 | — |
| Gastrointestinal | ||
| Nausea | 8 | 5 |
| Dry Mouth | 3 | 4 |
| Abdominal/Gastric Distress | 2 | 2 |
| Diarrhea | 2 | — |
| Constipation | 1 | 2 |
| Vomiting | 1 | 2 |
| Musculoskeletal | ||
| Musculoskeletal Aches/Pains | 1 | — |
| Neurological | ||
| Numbness | 2 | — |
| Paresthesia | 1 | — |
| Incoordination | 1 | — |
| Tremor | 1 | — |
| Skin | ||
| Skin Rash | 1 | — |
| Miscellaneous | ||
| Headache | 6 | 3 |
| Fatigue | 4 | 4 |
| Weakness | 2 | — |
| Sweating/Clamminess | 1 | — |
| *Events reported by at least 1% of BuSpar patients are included. —Incidence less than 1%. |
||
During its premarketing assessment, BuSpar was evaluated in over 3500 subjects. This section reports event frequencies for adverse events occurring in approximately 3000 subjects from this group who took multiple doses of BuSpar in the dose range for which BuSpar is being recommended (ie, the modal daily dose of BuSpar fell between 10 mg and 30 mg for 70% of the patients studied) and for whom safety data were systematically collected. The conditions and duration of exposure to BuSpar varied greatly, involving well-controlled studies as well as experience in open and uncontrolled clinical settings. As part of the total experience gained in clinical studies, various adverse events were reported. In the absence of appropriate controls in some of the studies, a causal relationship to BuSpar (buspirone hydrochloride) treatment cannot be determined. The list includes all undesirable events reasonably associated with the use of the drug.
The following enumeration by organ system describes events in terms of their relative frequency of reporting in this data base. Events of major clinical importance are also described in the PRECAUTIONS section.
The following definitions of frequency are used: Frequent adverse events are defined as those occurring in at least 1/100 patients. Infrequent adverse events are those occurring in 1/100 to 1/1000 patients, while rare events are those occurring in less than 1/1000 patients.
Frequent was nonspecific chest pain; infrequent were syncope, hypotension, and hypertension; rare were cerebrovascular accident, congestive heart failure, myocardial infarction, cardiomyopathy, and bradycardia.
Frequent were dream disturbances; infrequent were depersonalization, dysphoria, noise intolerance, euphoria, akathisia, fearfulness, loss of interest, dissociative reaction, hallucinations, involuntary movements, slowed reaction time, suicidal ideation, and seizures; rare were feelings of claustrophobia, cold intolerance, stupor, and slurred speech and psychosis.
Frequent were tinnitus, sore throat, and nasal congestion; infrequent were redness and itching of the eyes, altered taste, altered smell, and conjunctivitis; rare were inner ear abnormality, eye pain, photophobia, and pressure on eyes.
Rare were galactorrhea and thyroid abnormality.
Infrequent were flatulence, anorexia, increased appetite, salivation, irritable colon, and rectal bleeding; rare was burning of the tongue.
Infrequent were urinary frequency, urinary hesitancy, menstrual irregularity and spotting, and dysuria; rare were amenorrhea, pelvic inflammatory disease, enuresis, and nocturia.
Infrequent were muscle cramps, muscle spasms, rigid/stiff muscles, and arthralgias; rare was muscle weakness.
Infrequent were hyperventilation, shortness of breath, and chest congestion; rare was epistaxis.
Infrequent were decreased or increased libido; rare were delayed ejaculation and impotence.
Infrequent were edema, pruritus, flushing, easy bruising, hair loss, dry skin, facial edema, and blisters; rare were acne and thinning of nails.
Infrequent were increases in hepatic aminotransferases (SGOT, SGPT); rare were eosinophilia, leukopenia, and thrombocytopenia.
Infrequent were weight gain, fever, roaring sensation in the head, weight loss, and malaise; rare were alcohol abuse, bleeding disturbance, loss of voice, and hiccoughs.
Postmarketing experience has shown an adverse experience profile similar to that given above. Voluntary reports since introduction have included rare occurrences of allergic reactions (including urticaria), angioedema, cogwheel rigidity, dizziness (rarely reported as vertigo), dystonic reactions (including dystonia), ataxias, extrapyramidal symptoms, dyskinesias (acute and tardive), ecchymosis, emotional lability, serotonin syndrome, transient difficulty with recall, urinary retention, visual changes (including tunnel vision), parkinsonism, akathisia, restless leg syndrome, and restlessness. Because of the uncontrolled nature of these spontaneous reports, a causal relationship to BuSpar treatment has not been determined.
BuSpar (buspirone hydrochloride) is not a controlled substance.
In human and animal studies, buspirone has shown no potential for abuse or diversion and there is no evidence that it causes tolerance, or either physical or psychological dependence. Human volunteers with a history of recreational drug or alcohol usage were studied in two double-blind clinical investigations. None of the subjects were able to distinguish between BuSpar and placebo. By contrast, subjects showed a statistically significant preference for methaqualone and diazepam. Studies in monkeys, mice, and rats have indicated that buspirone lacks potential for abuse.
Following chronic administration in the rat, abrupt withdrawal of buspirone did not result in the loss of body weight commonly observed with substances that cause physical dependency.
Although there is no direct evidence that BuSpar causes physical dependence or drug-seeking behavior, it is difficult to predict from experiments the extent to which a CNS-active drug will be misused, diverted, and/or abused once marketed. Consequently, physicians should carefully evaluate patients for a history of drug abuse and follow such patients closely, observing them for signs of BuSpar misuse or abuse (eg, development of tolerance, incrementation of dose, drug-seeking behavior).
It is recommended that BuSpar not be used concomitantly with MAO inhibitors (see WARNINGS).
After addition of buspirone to the amitriptyline dose regimen, no statistically significant differences in the steady-state pharmacokinetic parameters (Cmax, AUC, and Cmin) of amitriptyline or its metabolite nortriptyline were observed.
After addition of buspirone to the diazepam dose regimen, no statistically significant differences in the steady-state pharmacokinetic parameters (Cmax, AUC, and Cmin) were observed for diazepam, but increases of about 15% were seen for nordiazepam, and minor adverse clinical effects (dizziness, headache, and nausea) were observed.
In a study in normal volunteers, concomitant administration of buspirone and haloperidol resulted in increased serum haloperidol concentrations. The clinical significance of this finding is not clear.
(see Inhibitors and Inducers of Cytochrome P450 3A4 [CYP3A4])
There is one report suggesting that the concomitant use of Desyrel® (trazodone hydrochloride) and buspirone may have caused 3- to 6-fold elevations on SGPT (ALT) in a few patients. In a similar study attempting to replicate this finding, no interactive effect on hepatic transaminases was identified.
Coadministration of buspirone with either triazolam or flurazepam did not appear to prolong or intensify the sedative effects of either benzodiazepine.
Because the effects of concomitant administration of buspirone with most other psychotropic drugs have not been studied, the concomitant use of buspirone with other CNS-active drugs should be approached with caution.
Buspirone has been shown in vitro to be metabolized by CYP3A4. This finding is consistent with the in vivo interactions observed between buspirone and the following:
In a study of nine healthy volunteers, coadministration of buspirone (10 mg as a single dose) with verapamil (80 mg t.i.d.) or diltiazem (60 mg t.i.d.) increased plasma buspirone concentrations (verapamil increased AUC and Cmax of buspirone 3.4-fold while diltiazem increased AUC and Cmax 5.5-fold and 4-fold, respectively.) Adverse events attributable to buspirone may be more likely during concomitant administration with either diltiazem or verapamil. Subsequent dose adjustment may be necessary and should be based on clinical assessment.
In a study in healthy volunteers, coadministration of buspirone (10 mg as a single dose) with erythromycin (1.5 g/day for 4 days) increased plasma buspirone concentrations (5-fold increase in Cmax and 6-fold increase in AUC). These pharmacokinetic interactions were accompanied by an increased incidence of side effects attributable to buspirone. If the two drugs are to be used in combination, a low dose of buspirone (eg, 2.5 mg b.i.d.) is recommended. Subsequent dose adjustment of either drug should be based on clinical assessment.
In a study in healthy volunteers, coadministration of buspirone (10 mg as a single dose) with grapefruit juice (200 mL double-strength t.i.d. for 2 days) increased plasma buspirone concentrations (4.3-fold increase in Cmax; 9.2-fold increase in AUC). Patients receiving buspirone should be advised to avoid drinking such large amounts of grapefruit juice.
In a study in healthy volunteers, coadministration of buspirone (10 mg as a single dose) with itraconazole (200 mg/day for 4 days) increased plasma buspirone concentrations (13-fold increase in Cmax and 19-fold increase in AUC). These pharmacokinetic interactions were accompanied by an increased incidence of side effects attributable to buspirone. If the two drugs are to be used in combination, a low dose of buspirone (eg, 2.5 mg q.d.) is recommended. Subsequent dose adjustment of either drug should be based on clinical assessment.
In a study of steady-state pharmacokinetics in healthy volunteers, coadministration of buspirone (2.5 or 5 mg b.i.d.) with nefazodone (250 mg b.i.d.) resulted in marked increases in plasma buspirone concentrations (increases up to 20-fold in Cmax and up to 50-fold in AUC) and statistically significant decreases (about 50%) in plasma concentrations of the buspirone metabolite 1-PP. With 5 mg b.i.d. doses of buspirone, slight increases in AUC were observed for nefazodone (23%) and its metabolites hydroxynefazodone (HO-NEF) (17%) and meta-chlorophenylpiperazine (9%). Slight increases in Cmax were observed for nefazodone (8%) and its metabolite HO-NEF (11%). Subjects receiving buspirone 5 mg b.i.d. and nefazodone 250 mg b.i.d experienced lightheadedness, asthenia, dizziness, and somnolence, adverse events also observed with either drug alone. If the two drugs are to be used in combination, a low dose of buspirone (eg, 2.5 mg q.d.) is recommended. Subsequent dose adjustment of either drug should be based on clinical assessment.
In a study in healthy volunteers, coadministration of buspirone (30 mg as a single dose) with rifampin (600 mg/day for 5 days) decreased the plasma concentrations (83.7% decrease in Cmax; 89.6% decrease in AUC) and pharmacodynamic effects of buspirone. If the two drugs are to be used in combination, the dosage of buspirone may need adjusting to maintain anxiolytic effect.
Substances that inhibit CYP3A4, such as ketoconazole or ritonavir, may inhibit buspirone metabolism and increase plasma concentrations of buspirone while substances that induce CYP3A4, such as dexamethasone or certain anticonvulsants (phenytoin, phenobarbital, carbamazepine), may increase the rate of buspirone metabolism. If a patient has been titrated to a stable dosage on buspirone, a dose adjustment of buspirone may be necessary to avoid adverse events attributable to buspirone or diminished anxiolytic activity. Consequently, when administered with a potent inhibitor of CYP3A4, a low dose of buspirone used cautiously is recommended. When used in combination with a potent inducer of CYP3A4 the dosage of buspirone may need adjusting to maintain anxiolytic effect.
Coadministration of buspirone with cimetidine was found to increase Cmax (40%) and Tmax (2–fold), but had minimal effects on the AUC of buspirone.
In vitro, buspirone does not displace tightly bound drugs like phenytoin, propranolol, and warfarin from serum proteins. However, there has been one report of prolonged prothrombin time when buspirone was added to the regimen of a patient treated with warfarin. The patient was also chronically receiving phenytoin, phenobarbital, digoxin, and Synthroid®. In vitro, buspirone may displace less firmly bound drugs like digoxin. The clinical significance of this property is unknown.
Therapeutic levels of aspirin, desipramine, diazepam, flurazepam, ibuprofen, propranolol, thioridazine, and tolbutamide had only a limited effect on the extent of binding of buspirone to plasma proteins (see CLINICAL PHARMACOLOGY).
Buspirone is not known to interfere with commonly employed clinical laboratory tests.
Synthroid® is the registered trademark of Abbott Laboratories.
Last updated on RxList: 7/6/2009
The administration of BuSpar to a patient taking a monoamine oxidase inhibitor (MAOI) may pose a hazard. There have been reports of the occurrence of elevated blood pressure when BuSpar (buspirone hydrochloride) has been added to a regimen including an MAOI. Therefore, it is recommended that BuSpar not be used concomitantly with an MAOI.
Because BuSpar has no established antipsychotic activity, it should not be employed in lieu of appropriate antipsychotic treatment.
Studies indicate that BuSpar is less sedating than other anxiolytics and that it does not produce significant functional impairment. However, its CNS effects in any individual patient may not be predictable. Therefore, patients should be cautioned about operating an automobile or using complex machinery until they are reasonably certain that buspirone treatment does not affect them adversely.
While formal studies of the interaction of BuSpar (buspirone hydrochloride) with alcohol indicate that buspirone does not increase alcohol-induced impairment in motor and mental performance, it is prudent to avoid concomitant use of alcohol and buspirone.
Because BuSpar does not exhibit cross-tolerance with benzodiazepines and other common sedative/hypnotic drugs, it will not block the withdrawal syndrome often seen with cessation of therapy with these drugs. Therefore, before starting therapy with BuSpar, it is advisable to withdraw patients gradually, especially patients who have been using a CNS-depressant drug chronically, from their prior treatment. Rebound or withdrawal symptoms may occur over varying time periods, depending in part on the type of drug, and its effective half-life of elimination.
The syndrome of withdrawal from sedative/hypnotic/anxiolytic drugs can appear as any combination of irritability, anxiety, agitation, insomnia, tremor, abdominal cramps, muscle cramps, vomiting, sweating, flu-like symptoms without fever, and occasionally, even as seizures.
Because buspirone can bind to central dopamine receptors, a question has been raised about its potential to cause acute and chronic changes in dopamine-mediated neurological function (eg, dystonia, pseudo-parkinsonism, akathisia, and tardive dyskinesia). Clinical experience in controlled trials has failed to identify any significant neuroleptic-like activity; however, a syndrome of restlessness, appearing shortly after initiation of treatment, has been reported in some small fraction of buspirone-treated patients. The syndrome may be explained in several ways. For example, buspirone may increase central noradrenergic activity; alternatively, the effect may be attributable to dopaminergic effects (ie, represent akathisia). See ADVERSE REACTIONS: Postmarketing Experience.
To assure safe and effective use of BuSpar, the following information and instructions should be given to patients:
There are no specific laboratory tests recommended.
No evidence of carcinogenic potential was observed in rats during a 24-month study at approximately 133 times the maximum recommended human oral dose; or in mice, during an 18-month study at approximately 167 times the maximum recommended human oral dose.
With or without metabolic activation, buspirone did not induce point mutations in five strains of Salmonella typhimurium (Ames Test) or mouse lymphoma L5178YTK+ cell cultures, nor was DNA damage observed with buspirone in Wi-38 human cells. Chromosomal aberrations or abnormalities did not occur in bone marrow cells of mice given one or five daily doses of buspirone.
Pregnancy Category B: No fertility impairment or fetal damage was observed in reproduction studies performed in rats and rabbits at buspirone doses of approximately 30 times the maximum recommended human dose. In humans, however, adequate and wellcontrolled studies during pregnancy have not been performed. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.
The effect of BuSpar (buspirone hydrochloride) on labor and delivery in women is unknown. No adverse effects were noted in reproduction studies in rats.
The extent of the excretion in human milk of buspirone or its metabolites is not known. In rats, however, buspirone and its metabolites are excreted in milk. BuSpar administration to nursing women should be avoided if clinically possible.
The safety and effectiveness of buspirone were evaluated in two placebo-controlled 6-week trials involving a total of 559 pediatric patients (ranging from 6 to 17 years of age) with GAD. Doses studied were 7.5 mg to 30 mg b.i.d. (15-60 mg/day). There were no significant differences between buspirone and placebo with regard to the symptoms of GAD following doses recommended for the treatment of GAD in adults. Pharmacokinetic studies have shown that, for identical doses, plasma exposure to buspirone and its active metabolite, 1-PP, are equal to or higher in pediatric patients than adults. No unexpected safety findings were associated with buspirone in these trials. There are no long-term safety or efficacy data in this population.
In one study of 6632 patients who received buspirone for the treatment of anxiety, 605 patients were ≥ 65 years old and 41 were ≥ 75 years old; the safety and efficacy profiles for these 605 elderly patients (mean age = 70.8 years) were similar to those in the younger population (mean age = 43.3 years). Review of spontaneously reported adverse clinical events has not identified differences between elderly and younger patients, but greater sensitivity of some older patients cannot be ruled out.
There were no effects of age on the pharmacokinetics of buspirone (see CLINICAL PHARMACOLOGY: Special Populations).
Buspirone is metabolized by the liver and excreted by the kidneys. A pharmacokinetic study in patients with impaired hepatic or renal function demonstrated increased plasma levels and a lengthened half-life of buspirone. Therefore, the administration of BuSpar to patients with severe hepatic or renal impairment cannot be recommended (see CLINICAL PHARMACOLOGY).
Last updated on RxList: 7/6/2009
In clinical pharmacology trials, doses as high as 375 mg/day were administered to healthy male volunteers. As this dose was approached, the following symptoms were observed: nausea, vomiting, dizziness, drowsiness, miosis, and gastric distress. A few cases of overdosage have been reported, with complete recovery as the usual outcome. No deaths have been reported following overdosage with BuSpar alone. Rare cases of intentional overdosage with a fatal outcome were invariably associated with ingestion of multiple drugs and/or alcohol, and a causal relationship to buspirone could not be determined. Toxicology studies of buspirone yielded the following LD50 values: mice, 655 mg/kg; rats, 196 mg/kg; dogs, 586 mg/kg; and monkeys, 356 mg/kg. These dosages are 160 to 550 times the recommended human daily dose.
General symptomatic and supportive measures should be used along with immediate gastric lavage. Respiration, pulse, and blood pressure should be monitored as in all cases of drug overdosage. No specific antidote is known to buspirone, and dialyzability of buspirone has not been determined.
BuSpar is contraindicated in patients hypersensitive to buspirone hydrochloride.
Last updated on RxList: 7/6/2009
The mechanism of action of buspirone is unknown. Buspirone differs from typical benzodiazepine anxiolytics in that it does not exert anticonvulsant or muscle relaxant effects. It also lacks the prominent sedative effect that is associated with more typical anxiolytics. In vitro preclinical studies have shown that buspirone has a high affinity for serotonin (5-HT1A) receptors. Buspirone has no significant affinity for benzodiazepine receptors and does not affect GABA binding in vitro or in vivo when tested in preclinical models.
Buspirone has moderate affinity for brain D2-dopamine receptors. Some studies do suggest that buspirone may have indirect effects on other neurotransmitter systems.
BuSpar is rapidly absorbed in man and undergoes extensive first-pass metabolism. In a radiolabeled study, unchanged buspirone in the plasma accounted for only about 1% of the radioactivity in the plasma. Following oral administration, plasma concentrations of unchanged buspirone are very low and variable between subjects. Peak plasma levels of 1 ng/mL to 6 ng/mL have been observed 40 to 90 minutes after single oral doses of 20 mg. The single-dose bioavailability of unchanged buspirone when taken as a tablet is on the average about 90% of an equivalent dose of solution, but there is large variability.
The effects of food upon the bioavailability of BuSpar have been studied in eight subjects. They were given a 20 mg dose with and without food; the area under the plasma concentration-time curve (AUC) and peak plasma concentration (Cmax) of unchanged buspirone increased by 84% and 116%, respectively, but the total amount of buspirone immunoreactive material did not change. This suggests that food may decrease the extent of presystemic clearance of buspirone (see DOSAGE AND ADMINISTRATION).
A multiple-dose study conducted in 15 subjects suggests that buspirone has nonlinear pharmacokinetics. Thus, dose increases and repeated dosing may lead to somewhat higher blood levels of unchanged buspirone than would be predicted from results of single-dose studies.
An in vitro protein binding study indicated that approximately 86% of buspirone is bound to plasma proteins. It was also observed that aspirin increased the plasma levels of free buspirone by 23%, while flurazepam decreased the plasma levels of free buspirone by 20%. However, it is not known whether these drugs cause similar effects on plasma levels of free buspirone in vivo, or whether such changes, if they do occur, cause clinically significant differences in treatment outcome. An in vitro study indicated that buspirone did not displace highly protein-bound drugs such as phenytoin, warfarin, and propranolol from plasma protein, and that buspirone may displace digoxin.
Buspirone is metabolized primarily by oxidation, which in vitro has been shown to be mediated by cytochrome P450 3A4 (CYP3A4). (See PRECAUTIONS: DRUG INTERACTIONS.) Several hydroxylated derivatives and a pharmacologically active metabolite, 1-pyrimidinylpiperazine (1-PP), are produced. In animal models predictive of anxiolytic potential, 1-PP has about one quarter of the activity of buspirone, but is present in up to 20-fold greater amounts. However, this is probably not important in humans: blood samples from humans chronically exposed to BuSpar (buspirone hydrochloride) do not exhibit high levels of 1-PP; mean values are approximately 3 ng/mL and the highest human blood level recorded among 108 chronically dosed patients was 17 ng/mL, less than 1/200th of 1-PP levels found in animals given large doses of buspirone without signs of toxicity.
In a single-dose study using 14C-labeled buspirone, 29% to 63% of the dose was excreted in the urine within 24 hours, primarily as metabolites; fecal excretion accounted for 18% to 38% of the dose. The average elimination half-life of unchanged buspirone after single doses of 10 mg to 40 mg is about 2 to 3 hours.
After single or multiple doses in adults, no significant differences in buspirone pharmacokinetics (AUC and Cmax) were observed between elderly and younger subjects or between men and women.
After multiple-dose administration of buspirone to patients with hepatic impairment, steady-state AUC of buspirone increased 13-fold compared with healthy subjects (see PRECAUTIONS).
After multiple-dose administration of buspirone to renally impaired (Clcr = 10–70 mL/min/1.73 m²) patients, steady-state AUC of buspirone increased 4-fold compared with healthy (Clcr ≥ 80 mL/min/1.73 m²) subjects (see PRECAUTIONS).
The effects of race on the pharmacokinetics of buspirone have not been studied.
Last updated on RxList: 7/6/2009
BuSpar®
(buspirone HCl, USP)
HOW TO USE:
BuSpar®
(buspirone HCl, USP) 15 mg and 30 mg Tablets in convenient DIVIDOSE®
tablet form
Response to buspirone varies among individuals. Your physician may find it necessary to adjust your dosage to obtain the proper response.
This DIVIDOSE tablet design makes dosage adjustments easy. Each tablet is scored and can be broken accurately to provide any of the following dosages.
| If your doctor prescribed the 30 mg tablet: |
|
If your doctor prescribed the 15 mg tablet: |
| 30 mg (the entire tablet) |
|
15 mg (the entire tablet) |
| 20 mg (two thirds of a tablet) |
|
10 mg (two thirds of a tablet) |
| 10 mg (one third of a tablet) |
|
5 mgm(one third of a tablet) |
| 15 mg (one half of a tablet) |
|
7.5 mg (one half of a tablet) |
To break a DIVIDOSE tablet accurately and easily, hold the tablet between your thumbs and index fingers close to the appropriate tablet score (groove) as shown in the photo. Then, with the tablet score facing you, apply pressure and snap the tablet segments apart (segments breaking incorrectly should not be used).
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Last updated on RxList: 7/6/2009
IMPORTANT NOTE: This is a summary and does not contain all possible information about this product. For complete information about this product or your specific health needs, ask your health care professional. Always seek the advice of your health care professional if you have any questions about this product or your medical condition. This information is not intended as individual medical advice and does not substitute for the knowledge and judgment of your health care professional. This information does not contain any assurances that this product is safe, effective, or appropriate for you.
BUSPIRONE - ORAL
(byou-SPY-rown)
COMMON BRAND NAME(S): Buspar
USES: This medication is used to treat anxiety. It may help you think more clearly, relax, worry less, and take part in everyday life. It may also help you to feel less jittery and irritable, and may control symptoms such as trouble sleeping, sweating, and pounding heartbeat. Buspirone is a medication for anxiety (anxiolytic) that works by affecting certain natural substances in the brain (neurotransmitters).
HOW TO USE: Take this medication by mouth, usually 2 or 3 times a day or as directed by your doctor. You may take this medication with or without food, but it is important to choose one way and always take it the same way so that the amount of drug absorbed will always be the same.
Buspirone may come in a tablet that can be split to get the correct dose for you. Follow the manufacturer's Patient Instruction Sheet or ask your pharmacist how to split the tablet to get your dose.
Limit the amount of grapefruit you may eat or drink (less than one quart a day) while being treated with this medication unless your doctor directs you otherwise. Grapefruit may increase the amount of buspirone in your bloodstream. Consult your pharmacist or doctor for more information.
Dosage is based on your medical condition and response to therapy. Use this medication regularly in order to get the most benefit from it. To help you remember, use it at the same times each day. When this medication is started, symptoms of anxiety (e.g., restlessness) may sometimes get worse before they improve. It may take up to a month or more to get the full effect of this medication.
Inform your doctor if your symptoms persist or worsen.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Rarely, patients taking buspirone may develop movement disorders such as shakiness (tremors), muscle stiffness, mask-like facial expression, jerky walking movements, or a condition known as tardive dyskinesia. In some cases, these conditions may be permanent. Tell your doctor immediately if you develop any unusual/uncontrolled movements (especially of the face, mouth, tongue, arms, or legs).
Seek immediate medical attention if any of these rare but serious side effects occur: easy bleeding/bruising, shortness of breath, chest pain, fast/irregular heartbeat.
A very serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction may include: rash, itching, swelling, severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist .
Contact your doctor for medical advice about side effects. The following numbers do not provide medical advice, but in the US you may report side effects to the Food and Drug Administration (FDA) at 1-800-FDA-1088. In Canada, you may call Health Canada at 1-866-234-2345.
PRECAUTIONS: Before taking buspirone, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies.
This medication should not be used if you have certain medical conditions. Before using this medication, consult your doctor if you have: kidney problems, liver problems.
Before using this medication, tell your doctor or pharmacist your medical history, especially of: bipolar disorder (manic-depression), Parkinson's disease.
This drug may make you dizzy or drowsy; use caution engaging in activities requiring alertness such as driving or using machinery. Limit alcoholic beverages.
If you are taking other medications for anxiety, do not suddenly stop them unless directed by your doctor. Buspirone will not prevent withdrawal symptoms from other medications, and your dose may need to be lowered slowly when you switch to buspirone. Discuss your treatment plan with your doctor. If you experience withdrawal symptoms, tell your doctor immediately.
During pregnancy, this medication should only be used when clearly needed. Tell your doctor if you are pregnant before using this medication. Discuss the risks and benefits with your doctor.
Buspirone may pass into breast milk. While there have been no reports of harm to nursing infants, breast-feeding while using this medication is not recommended. Consult your doctor before breast-feeding.
Buspirone should not be used with MAO inhibitors (e.g., furazolidone, isocarboxazid, linezolid, moclobemide, phenelzine, procarbazine, selegiline, tranylcypromine). Do not take buspirone within 2 weeks before, during and after treatment with MAO inhibitors. In some cases, a serious, possibly fatal, drug interaction may occur.
Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially of: alcohol, antidepressants (e.g., SSRIs such as fluoxetine, tricyclic antidepressants such as amitriptyline/nortriptyline, trazodone), benzodiazepines (e.g., lorazepam, clonazepam, diazepam), haloperidol, drugs that slow down the removal of buspirone from your body by affecting certain liver enzymes including azole antifungals (e.g., itraconazole, ketoconazole), macrolides (e.g., erythromycin), ritonavir, nefazodone, diltiazem, verapamil, drugs that speed up the removal of buspirone from your body by affecting certain liver enzymes including rifamycins (e.g., rifampin, rifabutin), corticosteroids (e.g., dexamethasone), and certain anticonvulsants (e.g., carbamazepine, phenytoin, phenobarbital).
Tell your doctor or pharmacist if you also take drugs that cause drowsiness such as: certain antihistamines (e.g., diphenhydramine), anti-seizure medications (e.g., valproic acid), medicine for sleep or anxiety (e.g., alprazolam, flurazepam, zolpidem), muscle relaxants, narcotic pain relievers (e.g., codeine), psychiatric medications (e.g., risperidone).
This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.
OVERDOSE: If overdose is suspected, contact your local poison control center or emergency room immediately. US residents can call the US national poison hotline at 1-800-222-1222. Canadian residents should call their local poison control center directly.
NOTES: Do not share this medication with others.
Keep all regular medical and laboratory appointments. If you are also taking trazodone, liver function tests may be performed regularly to check for side effects. Consult your doctor for more details.
MISSED DOSE: If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.
STORAGE: Store the US product in a tightly closed container at room temperature below 86 degrees F (30 degrees C) away from light and moisture.
Store the Canadian product in a tightly closed container at room temperature 59-86 degrees F (15-30 degrees C) away from light and moisture.
Do not store in the bathroom. Keep all medicines away from children and pets.
Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.
Information last revised July 2008 Copyright(c) 2008 First DataBank, Inc.
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