Carbidopa, an inhibitor of aromatic amino acid decarboxylation, is a white, crystalline compound, slightly soluble in water, with a molecular weight of 244.3. It is designated chemically as (–)-L-α-hydrazino-α-methyl-β-(3,4-dihydroxybenzene) propanoic acid monohydrate. Its empirical formula is C₁₀H₁₄N₂O₄•H₂O, and its structural formula is:

LODOSYN (Carbidopa) tablets contain 25 mg of carbidopa. Inactive ingredients are cellulose, FD&C Yellow 6, magnesium stearate and starch.

Tablet content is expressed in terms of anhydrous carbidopa which has a molecular weight of 226.3.

Last updated on RxList: 10/3/2008

LODOSYN is indicated for use with SINEMET (Carbidopa-Levodopa) or with levodopa in the treatment of the symptoms of idiopathic Parkinson's disease (paralysis agitans), postencephalitic parkinsonism, and symptomatic parkinsonism which may follow injury to the nervous system by carbon monoxide intoxication and/or manganese intoxication.

LODOSYN is for use with SINEMET (Carbidopa-Levodopa) in patients for whom the dosage of SINEMET (Carbidopa-Levodopa) provides less than adequate daily dosage (usually 70 mg daily) of carbidopa.

LODOSYN is for use with levodopa in the occasional patient whose dosage requirement of carbidopa and levodopa necessitates separate titration of each entity.

LODOSYN is used with SINEMET (Carbidopa-Levodopa) or with levodopa to permit the administration of lower doses of levodopa with reduced nausea and vomiting, more rapid dosage titration, and with a somewhat smoother response. However, patients with markedly irregular ("on-off") responses to levodopa have not been shown to benefit from the addition of carbidopa.

Since carbidopa prevents the reversal of levodopa effects caused by pyridoxine, supplemental pyridoxine (vitamin B6), can be given to patients when they are receiving carbidopa and levodopa concomitantly or as SINEMET (Carbidopa-Levodopa).

Although the administration of LODOSYN permits control of parkinsonism and Parkinson's disease with much lower doses of levodopa, there is no conclusive evidence at present that this is beneficial other than in reducing nausea and vomiting, permitting more rapid titration, and providing a somewhat smoother response to levodopa.

Certain patients who responded poorly to levodopa alone have improved when carbidopa and levodopa were given concurrently. This was most likely due to decreased peripheral decarboxylation of levodopa rather than to a primary effect of carbidopa on the peripheral nervous system. Carbidopa has not been shown to enhance the intrinsic efficacy of levodopa.

In considering whether to give LODOSYN with SINEMET (Carbidopa-Levodopa) or with levodopa to patients who have nausea and/or vomiting, the physician should be aware that, while many patients may be expected to improve, some may not. Since one cannot predict which patients are likely to improve, this can only be determined by a trial of therapy. It should be further noted that in controlled trials comparing carbidopa and levodopa with levodopa alone, about half the patients with nausea and/or vomiting on levodopa alone improved spontaneously despite being retained on the same dose of levodopa during the controlled portion of the trial.

Whether given with SINEMET (Carbidopa-Levodopa) or with levodopa, the optimal daily dosage of LODOSYN must be determined by careful titration. Most patients respond to a 1:10 proportion of carbidopa and levodopa, provided the daily dosage of carbidopa is 70 mg or more a day. The maximum daily dosage of carbidopa should not exceed 200 mg, since clinical experience with larger dosages is limited. If the patient is taking SINEMET (Carbidopa-Levodopa), the amount of carbidopa in SINEMET (Carbidopa-Levodopa) should be considered when calculating the total amount of LODOSYN to be administered each day.

Patients Receiving SINEMET (Carbidopa-Levodopa) Who Require Additional Carbidopa

Some patients taking SINEMET (Carbidopa-Levodopa) may not have adequate reduction in nausea and vomiting when the dosage of carbidopa is less than 70 mg a day, and the dosage of levodopa is less than 700 mg a day. When these patients are taking SINEMET 10-100** (Carbidopa-Levodopa), 25 mg of LODOSYN may be given with the first dose of SINEMET (Carbidopa-Levodopa) each day. Additional doses of 12.5 mg or 25 mg may be given during the day with each dose of SINEMET (Carbidopa-Levodopa). When patients are taking SINEMET 25-250*** (Carbidopa-Levodopa) or SINEMET 25-100^† (Carbidopa-Levodopa), 25 mg of LODOSYN may be given with any dose of SINEMET (Carbidopa-Levodopa) as required for optimum therapeutic response. The maximum daily dosage of carbidopa, given as LODOSYN and as SINEMET (Carbidopa-Levodopa), should not exceed 200 mg.

Patients Requiring Individual Titration of Carbidopa and Levodopa Dosage

Although SINEMET (Carbidopa-Levodopa) is the preferred method of carbidopa and levodopa administration, there may be an occasional patient who requires individually titrated doses of these two drugs. In these patients, LODOSYN (Carbidopa) should be initiated at a dosage of 25 mg three or four times a day. The two drugs should be given at the same time, starting with no more than one-fifth (20%) to one-fourth (25%) of the previous or recommended daily dosage of levodopa when given without LODOSYN (Carbidopa). In patients already receiving levodopa therapy, at least twelve hours should elapse between the last dose of levodopa and initiation of therapy with LODOSYN (Carbidopa) and levodopa. A convenient way to initiate therapy in these patients is in the morning following a night when the patient has not taken levodopa for at least twelve hours. Physicians who prescribe separate doses of LODOSYN and levodopa should be thoroughly familiar with the directions for use of each drug.

Dosage Adjustment

Dosage of LODOSYN may be adjusted by adding or omitting one-half or one tablet a day. Because both therapeutic and adverse responses occur more rapidly with combined therapy than when only levodopa is given, patients should be monitored closely during the dose adjustment period. Specifically, involuntary movements will occur more rapidly when LODOSYN and levodopa are given concomitantly than when levodopa is given without LODOSYN. The occurrence of involuntary movements may require dosage reduction. Blepharospasm may be a useful early sign of excess dosage in some patients.

Current evidence indicates other standard antiparkinsonian drugs may be continued while carbidopa and levodopa are being administered. However, the dosage of such other standard antiparkinsonian drugs may require adjustment.

Interruption of Therapy

Sporadic cases of a symptom complex resembling the Neuroleptic Malignant Syndrome (NMS) have been associated with dose reductions and withdrawal of SINEMET (Carbidopa-Levodopa) or SINEMET CR (Carbidopa-Levodopa) Sustained-Release. Patients should be observed carefully if abrupt reduction or discontinuation of SINEMET (Carbidopa-Levodopa) or SINEMET CR (Carbidopa-Levodopa) Sustained-Release is required, especially if the patient is receiving neuroleptics. (See WARNINGS.)

If general anesthesia is required, therapy may be continued as long as the patient is permitted to take fluids and medication by mouth. When therapy is interrupted temporarily, the patient should be observed for symptoms resembling NMS, and the usual daily dosage may be resumed as soon as the patient is able to take medication orally.

Tablets LODOSYN, 25 mg, are orange, round, compressed tablets, that are scored and coded 511 on one side and LODOSYN on the other.

They are supplied as follows:

NDC 0056-0511-68 bottles of 100.

Storage

Store at 25° C (77° F), excursions permitted to 15–30° C (59–86° F).

**SINEMET 10-100 (Carbidopa-Levodopa) contains 10 mg of carbidopa and 100 mg of levodopa.
***SINEMET 25-250 (Carbidopa-Levodopa) contains 25 mg of carbidopa and 250 mg of levodopa.
^†SINEMET 25-100 (Carbidopa-Levodopa) contains 25 mg of carbidopa and 100 mg of levodopa.

Manufactured by: MERCK & CO., INC. Whitehouse Station, NJ 08889, USA. Marketed by: Bristol Myers Squibb Co., Princeton, NJ 08543, USA. Revised September 2006. FDA Rev date: 12/18/2002

Last updated on RxList: 10/3/2008

Carbidopa has not been demonstrated to have any overt pharmacodynamic actions in the recommended doses. The only adverse reactions that have been observed have been with concomitant use of carbidopa with other drugs such as levodopa, and with carbidopa-levodopa combination products.

When LODOSYN is administered concomitantly with levodopa or carbidopa-levodopa combination products, the most common adverse reactions have included dyskinesias such as choreiform, dystonic, and other involuntary movements, and nausea. Other adverse reactions reported with LODOSYN when administered concomitantly with levodopa alone or carbidopa-levodopa combination products were psychotic episodes including delusions, hallucinations, and paranoid ideation, depression with or without development of suicidal tendencies, and dementia. Convulsions also have occurred; however, a causal relationship with concomitant use of LODOSYN and levodopa has not been established.

The following other adverse reactions have been reported with levodopa and carbidopa-levodopa combination products. These same adverse reactions may also occur when LODOSYN is administered with these products.

Body as a Whole: abdominal pain and distress, asthenia, chest pain, fatigue.

Cardiovascular: cardiac irregularities, hypertension, myocardial infarction, hypotension including orthostatic hypotension, palpitation, phlebitis, syncope.

Gastrointestinal: anorexia, bruxism, burning sensation of the tongue, constipation, dark saliva, development of duodenal ulcer, diarrhea, dry mouth, dyspepsia, dysphagia, flatulence, gastrointestinal bleeding, gastrointestinal pain, heartburn, hiccups, sialorrhea, taste alterations, vomiting.

Hematologic: hemolytic and non-hemolytic anemia, leukopenia, thrombocytopenia, agranulocytosis.

Hypersensitivity: angioedema, urticaria, pruritus, Henoch-Schonlein purpura, bullous lesions (including pemphigus-like reactions).

Metabolic: edema, weight gain, weight loss.

Musculoskeletal: back pain, leg pain, muscle cramps, shoulder pain.

Nervous System/Psychiatric: agitation, anxiety, ataxia, blepharospasm (which may be taken as an early sign of excess dosage; consideration of dosage reduction may be made at this time), bradykinetic episodes ("on-off" phenomenon), confusion, decreased mental acuity, disorientation, euphoria, dizziness, dream abnormalities including nightmares, extrapyramidal disorder, falling, gait abnormalities, headache, increased tremor, insomnia, memory impairment, muscle twitching, nervousness, numbness, paresthesia, peripheral neuropathy, somnolence, trismus, activation of latent Horner's syndrome, increased libido.

Respiratory: upper respiratory infection, dyspnea, pharyngeal pain, cough.

Skin: flushing, increased sweating, malignant melanoma (see also CONTRAINDICATIONS), rash, alopecia, dark sweat.

Special Senses: oculogyric crises, diplopia, blurred vision, dilated pupils.

Urogenital: dark urine, priapism, urinary frequency, urinary incontinence, urinary retention, urinary tract infection.

Laboratory Tests: abnormalities in alkaline phosphatase, SGOT (AST), SGPT (ALT), lactic dehydrogenase, bilirubin, blood urea nitrogen (BUN), Coombs test; elevated serum glucose; decreased hemoglobin and hematocrit; decreased white blood cell count and serum potassium; increased serum creatinine and uric acid; white blood cells, bacteria and blood in the urine; protein and glucose in the urine.

Miscellaneous: bizarre breathing patterns, faintness, hoarseness, hot flashes, malaise, neuroleptic malignant syndrome, sense of stimulation.

Caution should be exercised when the following drugs are administered concomitantly with LODOSYN (Carbidopa) given with levodopa or carbidopa-levodopa combination products.

Symptomatic postural hypotension has occurred when LODOSYN, given with levodopa or carbidopa-levodopa combination products, was added to the treatment of a patient receiving antihypertensive drugs. Therefore, when therapy with LODOSYN, given with or without levodopa or carbidopa-levodopa combination products, is started, dosage adjustment of the antihypertensive drug may be required.

For patients receiving monoamine oxidase inhibitors, see CONTRAINDICATIONS. Concomitant therapy with selegiline and carbidopa-levodopa may be associated with severe orthostatic hypotension not attributable to carbidopa-levodopa alone (see CONTRAINDICATIONS).

There have been rare reports of adverse reactions, including hypertension and dyskinesia, resulting from the concomitant use of tricyclic antidepressants and carbidopa-levodopa preparations.

Dopamine D2 receptor antagonists (e.g., phenothiazines, butyrophenones, risperidone) and isoniazid may reduce the therapeutic effects of levodopa. In addition, the beneficial effects of levodopa in Parkinson's disease have been reported to be reversed by phenytoin and papaverine. Patients taking these drugs with LODOSYN and levodopa or carbidopa-levodopa combination products should be carefully observed for loss of therapeutic response.

Iron salts may reduce the bioavailability of carbidopa and levodopa. The clinical relevance is unclear.

Although metoclopramide may increase the bioavailability of levodopa by increasing gastric emptying, metoclopramide may also adversely affect disease control by its dopamine receptor antagonistic properties.

Last updated on RxList: 10/3/2008

LODOSYN (Carbidopa) has no antiparkinsonian effect when given alone. It is indicated for use with SINEMET (Carbidopa-Levodopa) or levodopa. LODOSYN (Carbidopa) does not decrease adverse reactions due to central effects of levodopa.

When LODOSYN (Carbidopa) is to be given to carbidopa-naive patients who are being treated with levodopa alone, the two drugs should be given at the same time. At least twelve hours should elapse between the last dose of levodopa and initiation of therapy with LODOSYN (Carbidopa) and levodopa in combination. Start with no more than one-fifth (20%) to one-fourth (25%) of the previous daily dosage of levodopa when given without LODOSYN (Carbidopa). See the DOSAGE AND ADMINISTRATION section before initiating therapy.

As with levodopa, concomitant administration of LODOSYN and levodopa may cause involuntary movements and mental disturbances. These reactions are thought to be due to increased brain dopamine following administration of levodopa. All patients should be observed carefully for the development of depression with concomitant suicidal tendencies. Patients with past or current psychoses should be treated with caution. Because LODOSYN (Carbidopa) permits more levodopa to reach the brain and, thus, more dopamine to be formed, dyskinesias may occur at lower levodopa dosages and sooner with concomitant use of LODOSYN (Carbidopa) and levodopa or carbidopa-levodopa combination products than with levodopa alone. The occurrence of dyskinesias may require levodopa dosage reduction.

Levodopa, with or without LODOSYN, should be administered cautiously to patients with severe cardiovascular or pulmonary disease, bronchial asthma, renal, hepatic, or endocrine disease.

Care should be exercised in administering levodopa, with or without LODOSYN, to patients with a history of myocardial infarction who have residual atrial, nodal, or ventricular arrhythmias. In such patients, cardiac function should be monitored with particular care during the period of initial dosage adjustment, in a facility with provisions for intensive cardiac care.

As with levodopa alone there is a possibility of upper gastrointestinal hemorrhage in patients with a history of peptic ulcer.

Neuroleptic Malignant Syndrome (NMS): Sporadic cases of a symptom complex resembling NMS have been reported in association with dose reductions or withdrawal of certain antiparkinsonian agents such as levodopa, SINEMET (Carbidopa-Levodopa), or SINEMET CR (Carbidopa-Levodopa) Sustained-Release. Therefore, patients should be observed carefully when the dosage of levodopa is reduced abruptly or discontinued, especially if the patient is receiving neuroleptics.

NMS is an uncommon but life-threatening syndrome characterized by fever or hyperthermia. Neurological findings, including muscle rigidity, involuntary movements, altered consciousness, mental status changes; other disturbances, such as autonomic dysfunction, tachycardia, tachypnea, sweating, hyper- or hypotension; laboratory findings, such as creatine phosphokinase elevation, leukocytosis, myoglobinuria, and increased serum myoglobin, have been reported.

The early diagnosis of this condition is important for the appropriate management of these patients. Considering NMS as a possible diagnosis and ruling out other acute illnesses (e.g., pneumonia, systemic infection, etc.) is essential. This may be especially complex if the clinical presentation includes both serious medical illness and untreated or inadequately treated extrapyramidal signs and symptoms (EPS). Other important considerations in the differential diagnosis include central anticholinergic toxicity, heat stroke, drug fever, and primary central nervous system (CNS) pathology.

The management of NMS should include: 1) intensive symptomatic treatment and medical monitoring and 2) treatment of any concomitant serious medical problems for which specific treatments are available. Dopamine agonists, such as bromocriptine, and muscle relaxants, such as dantrolene, are often used in the treatment of NMS; however, their effectiveness has not been demonstrated in controlled studies.

General

As with levodopa alone, periodic evaluations of hepatic, hematopoietic, cardiovascular, and renal function are recommended during extended concomitant therapy with LODOSYN and levodopa, or with LODOSYN and SINEMET (Carbidopa-Levodopa), or any combination of these drugs.

Patients with chronic wide-angle glaucoma may be treated cautiously with LODOSYN and levodopa or SINEMET, or any combination of these drugs, just as with levodopa alone, provided the intraocular pressure is well controlled and the patient is monitored carefully for changes in intraocular pressure during therapy.

Laboratory Tests

Abnormalities in laboratory tests may include elevations of liver function tests such as alkaline phosphatase, SGOT (AST), SGPT (ALT), lactic dehydrogenase, and bilirubin. Abnormalities in blood urea nitrogen and positive Coombs test have also been reported. Commonly, levels of blood urea nitrogen, creatinine, and uric acid are lower during concomitant administration of carbidopa and levodopa than with levodopa alone.

Levodopa and carbidopa-levodopa combination products may cause a false-positive reaction for urinary ketone bodies when a test tape is used for determination of ketonuria. This reaction will not be altered by boiling the urine specimen. False-negative tests may result with the use of glucose-oxidase methods of testing for glucosuria.

Carcinogenesis, Mutagenesis, Impairment of Fertility

Carcinogenesis

There were no significant differences between treated and control rats with respect to mortality or neoplasia in a 96-week study of carbidopa at oral doses of 25, 45, or 135 mg/kg/day.

Combinations of carbidopa and levodopa (10-20, 10-50, 10-100 mg/kg/day) were given orally to rats for 106 weeks. No effect on mortality or incidence and type of neoplasia was seen when compared to concurrent controls.

Mutagenesis

Mutagenicity studies have not been performed with either carbidopa or the combination of carbidopa and levodopa.

Fertility

Carbidopa had no effect on the mating performance, fertility, or survival of the young when administered orally to rats at doses of 30, 60, or 120 mg/kg/day. The highest dose caused a moderate decrease in body weight gain in males.

The administration of carbidopa-levodopa at dose levels of 10-20, 10-50, or 10-100 mg/kg/day did not adversely affect the fertility of male or female rats, their reproductive performance, or the growth and survival of the young.

Pregnancy

Pregnancy Category C: There are no adequate and well-controlled studies with LODOSYN in pregnant women. It has been reported from individual cases that levodopa crosses the human placental barrier, enters the fetus, and is metabolized. Carbidopa concentrations in fetal tissue appeared to be minimal. LODOSYN should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Carbidopa, at doses as high as 120 mg/kg/day, was without teratogenic effects in the mouse or rabbit. In the rabbit, but not in the mouse, carbidopa-levodopa produced visceral anomalies, similar to those seen with levodopa alone, at approximately 7 times the maximum recommended human dose. The teratogenic effect of levodopa in rabbits was unchanged by the concomitant administration of carbidopa.

Nursing Mothers

It is not known whether carbidopa is excreted in human milk. Because many drugs are excreted in human milk, and because of their potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the nursing woman.

Pediatric Use

Safety and effectiveness in pediatric patients have not been established, and use of the drug in patients below the age of 18 is not recommended.

Last updated on RxList: 10/3/2008

No reports of overdose with LODOSYN have been received. Management of overdosage with carbidopa is the same as that with levodopa or carbidopa-levodopa preparations.

In the event of overdosage, general supportive measures should be employed, along with immediate gastric lavage. Intravenous fluids should be administered judiciously, and an adequate airway maintained. Electrocardiographic monitoring should be instituted and the patient carefully observed for the development of arrhythmias; if required, appropriate antiarrhythmic therapy should be given. The possibility that the patient may have taken other drugs as well as LODOSYN should be taken into consideration. To date, no experience has been reported with dialysis; hence, its value in overdosage is not known. Pyridoxine is not effective in reversing the actions of LODOSYN.

Based on studies in which high doses of levodopa and/or carbidopa were administered, a significant proportion of rats and mice given single oral doses of levodopa of approximately 1500-2000 mg/kg are expected to die. A significant proportion of infant rats of both sexes are expected to die at a dose of 800 mg/kg. A significant proportion of rats are expected to die after treatment with similar doses of carbidopa. The addition of carbidopa in a 1:10 ratio with levodopa increases the dose at which a significant proportion of mice are expected to die to 3360 mg/kg.

LODOSYN is contraindicated in patients with known hypersensitivity to any component of this drug.

Nonselective monoamine oxidase (MAO) inhibitors are contraindicated for use with levodopa or carbidopa-levodopa combination products with or without LODOSYN. These inhibitors must be discontinued at least two weeks prior to initiating therapy with levodopa. SINEMET (Carbidopa-Levodopa), or levodopa may be administered concomitantly with the manufacturer's recommended dose of an MAO inhibitor with selectivity for MAO type B (e.g., selegiline HCl) (see PRECAUTIONS: DRUG INTERACTIONS).

Levodopa or carbidopa-levodopa products, with or without LODOSYN, are contraindicated in patients with narrow-angle glaucoma.

Because levodopa or carbidopa-levodopa products, with or without LODOSYN, may activate a malignant melanoma, they should not be used in patients with suspicious, undiagnosed skin lesions or a history of melanoma.

Last updated on RxList: 10/3/2008

Parkinson's disease is a progressive, neurodegenerative disorder of the extrapyramidal nervous system affecting the mobility and control of the skeletal muscular system. Its characteristic features include resting tremor, rigidity, and bradykinetic movements. Symptomatic treatments, such as levodopa therapies, may permit the patient better mobility.

Mechanism of Action

Current evidence indicates that symptoms of Parkinson's disease are related to depletion of dopamine in the corpus striatum. Administration of dopamine is ineffective in the treatment of Parkinson's disease apparently because it does not cross the blood-brain barrier. However, levodopa, the metabolic precursor of dopamine, does cross the blood-brain barrier, and presumably is converted to dopamine in the brain. This is thought to be the mechanism whereby levodopa relieves symptoms of Parkinson's disease.

Pharmacodynamics

When levodopa is administered orally it is rapidly decarboxylated to dopamine in extracerebral tissues so that only a small portion of a given dose is transported unchanged to the central nervous system. For this reason, large doses of levodopa are required for adequate therapeutic effect and these may often be accompanied by nausea and other adverse reactions, some of which are attributable to dopamine formed in extracerebral tissues.

The incidence of levodopa-induced nausea and vomiting is less when LODOSYN is used with levodopa than when levodopa is used without LODOSYN. In many patients this reduction in nausea and vomiting will permit more rapid dosage titration.

Carbidopa inhibits decarboxylation of peripheral levodopa. Carbidopa has not been demonstrated to have any overt pharmacodynamic actions in the recommended doses. It does not appear to cross the blood-brain barrier readily and does not affect the metabolism of levodopa within the central nervous system at doses of carbidopa that are recommended for maximum effective inhibition of peripheral decarboxylation of levodopa.

Since its decarboxylase-inhibiting activity is limited primarily to extracerebral tissues, administration of carbidopa with levodopa makes more levodopa available for transport to the brain. However, since levodopa and carbidopa compete with certain amino acids for transport across the gut wall, the absorption of levodopa and carbidopa may be impaired in some patients on a high protein diet.

Pharmacokinetics

Carbidopa reduces the amount of levodopa required to produce a given response by about 75% and, when administered with levodopa, increases both plasma levels and the plasma half-life of levodopa, and decreases plasma and urinary dopamine and homovanillic acid.

In clinical pharmacologic studies, simultaneous administration of separate tablets of carbidopa and levodopa produced greater urinary excretion of levodopa in proportion to the excretion of dopamine when compared to the two drugs administered at separate times.

Supplemental pyridoxine (vitamin B₆) can be given to patients when they are receiving carbidopa and levodopa concomitantly or as SINEMET* CR (Carbidopa-Levodopa) Sustained-Release or SINEMET* (Carbidopa-Levodopa). Previous reports in the medical literature cautioned that high doses of vitamin B₆ should not be taken by patients on levodopa therapy alone because exogenously administered pyridoxine would enhance the metabolism of levodopa to dopamine. The introduction of carbidopa to levodopa therapy, which inhibits the peripheral decarboxylation of levodopa to dopamine, counteracts the metabolic-enhancing effect of pyridoxine.

Carbidopa is combined with levodopa in SINEMET (Carbidopa-Levodopa) and SINEMET CR (Carbidopa-Levodopa) Sustained-Release tablets. These combination tablets are available in three strengths for SINEMET: SINEMET 10-100 (Carbidopa-Levodopa), SINEMET 25-250 (Carbidopa-Levodopa) (1:10 ratio of carbidopa to levodopa) and SINEMET 25-100 (Carbidopa-Levodopa) (1:4 ratio of carbidopa to levodopa), and in two strengths for SINEMET CR: SINEMET CR 50-200 (Carbidopa-Levodopa) Sustained-Release and SINEMET CR 25-100 (Carbidopa-Levodopa) Sustained-Release (1:4 ratio of carbidopa to levodopa). Clinical trials show that these ratios of carbidopa and levodopa provide useful therapeutic effects in most patients.

Last updated on RxList: 10/3/2008

No information provided. Please refer to the WARNINGS and PRECAUTIONS sections.

Last updated on RxList: 10/3/2008

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.

CARBIDOPA - ORAL

(kar-beh-DOE-puh)

COMMON BRAND NAME(S): Lodosyn

USES: Carbidopa is used with levodopa or the combination levodopa/carbidopa to treat the symptoms of Parkinson's disease or Parkinson-like symptoms (e.g., shakiness, stiffness, difficulty moving). Carbidopa must be taken together with levodopa to be effective. Used alone, carbidopa has no effect on Parkinson's symptoms. It is used to improve the effect of levodopa and reduce some levodopa side effects (e.g., nausea, vomiting).

Carbidopa is known as an enzyme blocker. It works by preventing the breakdown of levodopa in the bloodstream. This allows more levodopa to enter the brain, where it can decrease Parkinson's symptoms. By helping more levodopa get into the brain so that less stays in the bloodstream, carbidopa can reduce some of levodopa's side effects such as nausea. This may allow your doctor to increase your dose of levodopa more quickly to find the best dose for you.

HOW TO USE: Take this medication by mouth with food along with your levodopa or levodopa/carbidopa doses, exactly as directed by your doctor. If you are taking carbidopa for the first time, wait at least 12 hours after your last levodopa dose before starting this medication. Your doctor will usually reduce your levodopa dose when starting carbidopa to prevent side effects from too much dopamine. Be sure to follow your doctor's instructions closely.

Avoid high-protein diets because they may prevent absorption of this medication. Separate your dose of this medication as many hours as possible from any iron supplements or products containing iron (e.g., multivitamins with minerals) you may take. Iron can reduce the amount of carbidopa and levodopa available to the body.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same times each day. Dosage is based on your medical condition and response to therapy. Consult your doctor or pharmacist regarding your dosing schedule.

Do not stop taking this medication without consulting your doctor. Some conditions may become worse when the drug is quickly reduced or suddenly stopped. Your dose may need to be gradually reduced. (See also Side Effects section.)

Inform your doctor if your condition does not improve or if it worsens.

SIDE EFFECTS: Side effects with carbidopa are rare and usually occur due to the effect of levodopa or other drugs used along with this medication. Consult the Side Effects information of the levodopa-containing product(s) as well as any other drugs you are using. If you have any questions or notice any effects, consult your doctor or pharmacist.

Tell your doctor immediately if you notice worsening involuntary muscle movements/spasms, greatly increased eye blinking/twitching, or mental/mood changes (e.g., confusion, depression, hallucinations, thoughts of suicide). Your doctor may decide to lower your levodopa dose.

Dizziness, nausea, and vomiting may occur. If any of these effects persist or worsen, contact your doctor or pharmacist promptly.

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.

Tell your doctor immediately if any of these unlikely but serious side effects occur: irregular heartbeat, fainting.

Tell your doctor immediately if any of these rare but very serious side effects occur: easy bleeding/bruising, signs of infection (e.g., fever, persistent sore throat), change in the appearance/size of moles or other unusual skin changes, tingling of the hands/feet, vision changes (e.g., blurred/double vision).

Seek immediate medical attention if any of these rare but very serious side effects occur: chest pain, seizures, vomit that looks like coffee grounds, black/tarry stools.

Abruptly stopping or reducing the dose of this medication may rarely cause a serious (sometimes fatal) condition (neuroleptic malignant syndrome). Seek immediate medical attention if any of these rare but very serious side effects occur: fast/shallow breathing, confusion, severe dizziness/fainting, high fever, muscle stiffness, unusual sweating.

For males, in the very unlikely event you have a painful or prolonged erection (lasting more than 4 hours), stop using this drug and seek immediate medical attention or permanent problems could occur.

A very serious allergic reaction is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction 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 this medication, 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 medicine, consult your doctor or pharmacist if you have: certain eye problem (narrow-angle glaucoma), past or present skin cancer (e.g., melanoma, undiagnosed skin lesions).

Before using this medication, tell your doctor or pharmacist your medical history, especially of: adrenal gland problems, breathing problems (e.g., asthma, emphysema), diabetes, certain eye problem (wide-angle glaucoma), heart or blood vessel problems (e.g., arrhythmias, heart attack, angina), kidney disease, liver disease, mental/mood disorders (e.g., depression, schizophrenia), thyroid problem, peptic ulcer, seizure.

This drug may make you dizzy or cause blurred vision; use caution engaging in activities requiring alertness or clear vision such as driving or using machinery. Avoid alcoholic beverages.

To minimize lightheadedness, get up slowly when rising from a sitting or lying position.

Before having surgery, tell your doctor or dentist that you are taking this medication.

If you have diabetes, levodopa and carbidopa may make it harder to control your blood sugar levels. Check your blood sugar levels regularly as directed by your doctor. Tell your doctor immediately if you have any symptoms of high blood sugar such as increased thirst and urination. Your anti-diabetic diet or medication may need to be adjusted.

This medication should be used only when clearly needed during pregnancy. Discuss the risks and benefits with your doctor.

Carbidopa combined with levodopa may pass into breast milk and could affect milk production. Because of the potential risk to the infant, breast-feeding while using this drug is not recommended. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: See also How to Use Section.

Your healthcare professional (e.g., doctor or pharmacist) may already be aware of any possible drug interactions and may be monitoring you for it. Do not stop or change the dosage of any medicine without checking with them first.

Avoid taking MAO inhibitors (e.g., furazolidone, isocarboxazid, linezolid, moclobemide, phenelzine, procarbazine, rasagiline, selegiline, tranylcypromine) within 2 weeks before, during, and after treatment with this medication. In some cases a serious (possibly fatal) drug interaction may occur.

Certain MAO inhibitors (rasagiline, selegiline) may be used cautiously with close monitoring by your doctor.

If you are currently using any of these medications listed above, tell your doctor or pharmacist before starting carbidopa. If you are taking rasagiline or selegiline for Parkinson's disease, ask your doctor if you should continue taking it.

Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially: all levodopa-containing products, medicine for high blood pressure (e.g., guanethidine, methyldopa, reserpine), antidepressants (e.g., tricyclics such as amitriptyline/nortriptyline), antipsychotics (e.g., chlorpromazine, thioridazine, risperidone), metoclopramide, phenytoin, papaverine, tryptophan (e.g., l-tryptophan, oxitriptan).

This medication may interfere with certain laboratory tests (including urine glucose/ketone tests), possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.

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. Symptoms of overdose may include: irregular heartbeat, seizures.

NOTES: Do not share this medication with others.

Laboratory and/or medical tests (e.g., blood count, heart/kidney/liver function) may be performed to monitor your progress.

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 at room temperature between 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.