Guanfacine hydrochloride is a centrally acting antihypertensive with a2-adrenoceptor agonist properties in tablet form for oral administration.

The chemical name of guanfacine hydrochloride is N-Amidino-2-(2,6-dichlorophenyl) acetamide monohydrochloride and its molecular weight is 282.55. Its structural formula is:

C₉H₉CI₂N₃O•HCI

Guanfacine hydrochloride is a white to off-white powder; sparingly soluble in water and alcohol and slightly soluble in acetone.

Each tablet, for oral administration, contains guanfacine hydrochloride equivalent to 1 mg or 2 mg guanfacine. The tablets contain the following inactive ingredients:

1 mg - anhydrous lactose, FD&C Red 40 aluminum lake, microcrystalline cellulose, povidone, stearic acid.
2 mg - anhydrous lactose, D&C Yellow 10 aluminum lake, FD&C Red 40 aluminum lake, microcrystalline cellulose, povidone, stearic acid.

Last updated on RxList: 12/6/2007

Guanfacine hydrochloride tablets are indicated in the management of hypertension. Guanfacine may be given alone or in combination with other antihypertensive agents, especially thiazide-type diuretics.

The recommended initial dose of guanfacine (as the hydrochloride) when given alone or in combination with another antihypertensive drug is 1 mg daily given at bedtime to minimize somnolence. If after 3 to 4 weeks of therapy, 1 mg does not give a satisfactory result, a dose of 2 mg may be given, although most of the effect of guanfacine is seen at 1 mg (see CLINICAL PHARMACOLOGY). Higher daily doses have been used, but adverse reactions increase significantly with doses above 3 mg/day.

The frequency of rebound hypertension is low, but it can occur. When rebound occurs, it does so after 2-4 days, which is delayed compared with clonidine hydrochloride. This is consistent with the longer half-life of guanfacine. In most cases, after abrupt withdrawal of guanfacine, blood pressure returns to pretreatment levels slowly (within 2-4 days) without ill effects.

Guanfacine hydrochloride is available in 2 tablet strengths of guanfacine (as the hydrochloride) as follows:

Guanfacine Hydrochloride Tablets 1 mg, are pink, round tablets, debossed with WATSON 444 and are available in bottles of 100.

Guanfacine Hydrochloride Tablets 2 mg, are peach, round tablets, debossed with WATSON 453 and are available in bottles of 100.

Bottles of 100 tablets are supplied with child-resistant closures.

Store at controlled room temperature 15°-30°C (59°-86°F).

Dispense in a tight, light-resistant container.

Watson Laboratories, Inc. Corona, CA 92880 USA. Revised: April 2003. FDA rev date: 3/12/2002

Last updated on RxList: 12/6/2007

Adverse reactions noted with guanfacine are similar to those of other drugs of the central a2 adrenoreceptor agonist class: dry mouth, sedation (somnolence), weakness (asthenia), dizziness, constipation, and impotence. While the reactions are common, most are mild and tend to disappear on continued dosing.

Skin rash with exfoliation has been reported in a few cases; although clear cause and effect relationships to guanfacine could not be established, should a rash occur, guanfacine should be discontinued and the patient monitored appropriately.

In the dose-response monotherapy study described under CLINICAL PHARMACOLOGY, the frequency of the most commonly observed adverse reactions showed a dose relationship from 0.5 to 3 mg as follows:

Adverse Reaction	Placebo	0.5 mg	1 mg	2 mg	3 mg
	n=59	n=60	n=61	n=60	n=59
Dry Mouth	0%	10%	10%	42%	54%
Somnolence	8%	5%	10%	13%	39%
Asthenia	0%	2%	3%	7%	3%
Dizziness	8%	12%	2%	8%	15%
Headache	8%	13%	7%	5%	3%
Impotence	0%	0%	0%	7%	3%
Constipation	0%	2%	0%	5%	15%
Fatigue	2%	2%	5%	8%	10%

The percent of patients who dropped out because of adverse reactions are shown below for each dosage group.

	Placebo	0.5 mg	1 mg	2 mg	3 mg
Percent dropouts	0%	2%	5%	13%	32%

The most common reasons for dropouts among patients who received guanfacine were dry mouth, somnolence, dizziness, fatigue, weakness, and constipation.

In the 12-week placebo-controlled, dose-response study of guanfacine administered with 25 mg chlorthalidone at bedtime, the frequency of the most commonly observed adverse reactions showed a clear dose relationship from 0.5 to 3 mg as follows:

Adverse Reaction	Placebo	0.5 mg	1 mg	2 mg	3 mg
	n=73	n=72	n=72	n=72	n=72
Dry mouth	5 (7%)	4 (5%)	6 (8%)	8 (11%)	20 (28%)
Somnolence	1 (1%)	3 (4%)	0 (0%)	1 (1%)	10 (14%)
Asthenia	0 (0%)	2 (3%)	0 (0%)	2 (2%)	7 (10%)
Dizziness	2 (2%)	1 (1%)	3 (4%)	6 (8%)	3 (4%)
Headache	3 (4%)	4 (3%)	3 (4%)	1 (1%)	2 (2%)
Impotence	1 (1%)	1 (0%)	0 (0%)	1 (1%)	3 (4%)
Constipation	0 (0%)	0 (0%)	0 (0%)	1 (1%)	1 (1%)
Fatigue	3 (3%)	2 (3%)	2 (3%)	5 (6%)	3 (4%)

There were 41 premature terminations because of adverse reactions in this study. The percent of patients who dropped out and the dose at which the dropout occurred were as follows:

Dose:	Placebo	0.5 mg	1 mg	2 mg	3 mg
Percent dropouts	6.90%	4.20%	3.20%	6.90%	8.30%

Reasons for dropouts among patients who received guanfacine were: somnolence, headache, weakness, dry mouth, dizziness, impotence, insomnia, constipation, syncope, urinary incontinence, conjunctivitis, paresthesia, and dermatitis.

In a second 12-week placebo-controlled combination therapy study in which the dose could be adjusted upward to 3 mg per day in 1-mg increments at 3-week intervals, i.e., a setting more similar to ordinary clinical use, the most commonly recorded reactions were: dry mouth, 47%; constipation, 16%; fatigue, 12%; somnolence, 10%; asthenia, 6%; dizziness, 6%; headache, 4%; and insomnia, 4%.

Reasons for dropouts among patients who received guanfacine were: somnolence, dry mouth, dizziness, impotence, constipation, confusion, depression, and palpitations.

In the clonidine/guanfacine comparison described in CLINICAL PHARMACOLOGY, the most common adverse reactions noted were as follows:

Adverse Reactions	Guanfacine	Clonidine
	(n=279)	(n=278)
Dry Mouth	30%	37%
Somnolence	21%	35%
Dizziness	11%	8%
Constipation	10%	5%
Fatigue	9%	8%
Headache	4%	4%
Insomnia	4%	3%

Adverse reactions occurring in 3% or less of patients in the three controlled trials of guanfacine with a diuretic were:

Cardiovascular - bradycardia, palpitations, substernal pain

Gastrointestinal - abdominal pain, diarrhea, dyspepsia, dysphagia, nausea

CNS - amnesia, confusion, depression, insomnia, libido decrease

ENT disorders - rhinitis, taste perversion, tinnitus

Eye disorders - conjunctivitis, iritis, vision disturbance

Musculoskeletal - leg cramps, hypokinesia

Respiratory - dyspnea

Dermatologic - dermatitis, pruritus, purpura, sweating

Urogenital - testicular disorder, urinary incontinence

Other - malaise, paresthesia, paresis

Adverse reaction reports tend to decrease over time. In an open-label trial of one year's duration, 580 hypertensive subjects were given guanfacine, titrated to achieve goal blood pressure, alone (51%), with diuretic (38%), with beta blocker (3%), with diuretic plus beta blocker (6%), or with diuretic plus vasodilator (2%). The mean daily dose of guanfacine reached was 4.7 mg.

Adverse Reaction	Incidence of adverse reactions at any time during the study	Incidence of adverse reactions at end of one year
	n=580	n=580
Dry Mouth	60%	15%
Drowsiness	33%	6%
Dizziness	15%	1%
Constipation	14%	3%
Weakness	5%	1%
Headache	4%	0.20%
Insomnia	5%	0%

There were 52 (8.9%) dropouts due to adverse effects in this 1-year trial. The causes were: dry mouth (n=20), weakness (n=12), constipation (n=7), somnolence (n=3), nausea (n=3), orthostatic hypotension (n=2), insomnia (n=1), rash (n=1), nightmares (n=1), headache (n=1), and depression (n=1).

Postmarketing Experience: An open-label postmarketing study involving 21,718 patients was conducted to assess the safety of guanfacine (as the hydrochloride) 1 mg/day given at bedtime for 28 days. Guanfacine was administered with or without other antihypertensive agents. Adverse events reported in the postmarketing study at an incidence greater than 1% included dry mouth, dizziness, somnolence, fatigue, headache, and nausea. The most commonly reported adverse events in this study were the same as those observed in controlled clinical trials.

Less frequent, possibly guanfacine-related events observed in the postmarketing study and/or reported spontaneously include:

BODY AS A WHOLE: asthenia, chest pain, edema, malaise, tremor

CARDIOVASCULAR: bradycardia, palpitations, syncope, tachycardia

CENTRAL NERVOUS SYSTEM: paresthesias, vertigo

EYE DISORDERS: blurred vision

GASTROINTESTINAL SYSTEM: abdominal pain, constipation, diarrhea, dyspepsia

LIVER AND BILIARY SYSTEM: abnormal liver function tests

MUSCULOSKELETAL SYSTEM: arthralgia, leg cramps, leg pain, myalgia

PSYCHIATRIC: agitation, anxiety, confusion, depression, insomnia, nervousness

REPRODUCTIVE SYSTEM, MALE: impotence

RESPIRATORY SYSTEM: dyspnea

SKIN AND APPENDAGES: alopecia, dermatitis, exfoliative dermatitis, pruritus, rash

SPECIAL SENSES: alterations in taste

URINARY SYSTEM: nocturia, urinary frequency

Rare, serious disorders with no definitive cause and effect relationship to guanfacine have been reported spontaneously and/or in the postmarketing study. These events include acute renal failure, cardiac fibrillation, cerebrovascular accident, congestive heart failure, heart block, and myocardial infarction.

DRUG ABUSE AND DEPENDENCE

No reported abuse or dependence has been associated with the administration of guanfacine.

The potential for increased sedation when guanfacine is given with other CNS-depressant drugs should be appreciated.

The administration of guanfacine concomitantly with a known microsomal enzyme inducer (phenobarbital or phenytoin) to two patients with renal impairment reportedly resulted in significant reductions in elimination half-life and plasma concentration. In such cases, therefore, more frequent dosing may be required to achieve or maintain the desired hypotensive response. Further, if guanfacine is to be discontinued in such patients, careful tapering of the dosage may be necessary in order to avoid rebound phenomena (see Rebound above).

Anticoagulants

Ten patients who were stabilized on oral anticoagulants were given guanfacine, 1-2 mg/day, for 4 weeks. No changes were observed in the degree of anticoagulation.

In several well-controlled studies, guanfacine was administered together with diuretics with no drug interactions reported. In the long-term safety studies, guanfacine was given concomitantly with many drugs without evidence of any interactions. The principal drugs given (number of patients in parentheses) were: cardiac glycosides (115), sedatives and hypnotics (103), coronary vasodilators (52), oral hypoglycemics (45), cough and cold preparations (45), NSAIDs (38), antihyperlipidemics (29), antigout drugs (24), oral contraceptives (18), bronchodilators (13), insulin (10), and beta blockers (10).

Last updated on RxList: 12/6/2007

No information provided.

General

Like other antihypertensive agents, guanfacine should be used with caution in patients with severe coronary insufficiency, recent myocardial infarction, cerebrovascular disease or chronic renal or hepatic failure.

Sedation

Guanfacine, like other orally active central a2 adrenergic agonists, causes sedation or drowsiness, especially when beginning therapy. These symptoms are dose-related (see ADVERSE REACTIONS). When guanfacine is used with other centrally active depressants (such as phenothiazines, barbiturates, or benzodiazepines), the potential for additive sedative effects should be considered.

Rebound

Abrupt cessation of therapy with orally active central a2 adrenergic agonists may be associated with increases (from depressed on-therapy levels) in plasma and urinary catecholamines, symptoms of "nervousness and anxiety" and, less commonly, increases in blood pressure to levels significantly greater than those prior to therapy.

Laboratory Tests

In clinical trials, no clinically relevant laboratory test abnormalities were identified as causally related to drug during short-term treatment with guanfacine.

Drug/Laboratory Test Interactions

No laboratory test abnormalities related to the use of guanfacine have been identified.

Carcinogenesis, Mutagenesis, Impairment of Fertility

No carcinogenic effect was observed in studies of 78 weeks in mice at doses more than 150 times the maximum recommended human dose and 102 weeks in rats at doses more than 100 times the maximum recommended human dose. In a variety of test models, guanfacine was not mutagenic.

No adverse effects were observed in fertility studies in male and female rats.

Pregnancy Category B

Administration of guanfacine to rats at 70 times the maximum recommended human dose and to rabbits at 20 times the maximum recommended human dose resulted in no evidence of harm to the fetus. Higher doses (100 and 200 times the maximum recommended human dose in rabbits and rats respectively) were associated with reduced fetal survival and maternal toxicity. Rat experiments have shown that guanfacine crosses the placenta.

There are, however, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.

Labor and Delivery

Guanfacine is not recommended in the treatment of acute hypertension associated with toxemia of pregnancy. There is no information available on the effects of guanfacine on the course of labor and delivery.

Nursing Mothers

It is not known whether guanfacine is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when guanfacine hydrochloride is administered to a nursing woman. Experiments with rats have shown that guanfacine is excreted in the milk.

Pediatric Use

Safety and effectiveness in pediatric patients under 12 years of age have not been demonstrated. Therefore, the use of guanfacine in this age group is not recommended. There have been spontaneous postmarketing reports of mania and aggressive behavioral changes in pediatric patients with attention-deficit hyperactivity disorder (ADHD) receiving guanfacine. The reported cases were from a single center. All patients had medical or family risk factors for bipolar disorder. All patients recovered upon discontinuation of guanfacine HCl.

Geriatric Use

Clinical studies of guanfacine did not include sufficient numbers of subjects aged 65 and over to determine whether they responded differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients.

In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal or cardiac function, and of concomitant disease or other drug therapy (see CLINICAL PHARMACOLOGY, Pharmacokinetics).

Last updated on RxList: 12/6/2007

Signs and Symptoms: Drowsiness, lethargy, bradycardia, and hypotension have been observed following overdose with guanfacine.

A 25-year-old female intentionally ingested 60 mg. She presented with severe drowsiness and bradycardia of 45 beats/minute. Gastric lavage was performed and an infusion of isoproterenol (0.8 mg in 12 hours) was administered. She recovered quickly and without sequelae.

A 28-year-old female who ingested 30-40 mg developed only lethargy, was treated with activated charcoal and a cathartic, was monitored for 24 hours, and was discharged in good health.

A 2-year-old male weighing 12 kg, who ingested up to 4 mg of guanfacine, developed lethargy. Gastric lavage (followed by activated charcoal and sorbitol slurry via NG tube) removed some tablet fragments within 2 hours after ingestion, and vital signs were normal.

During 24-hours observation in ICU, systolic pressure was 58 and heart rate 70 at 16 hours postingestion. No intervention was required, and child was discharged fully recovered the next day.

Treatment of Overdosage: Gastric lavage and supportive therapy as appropriate. Guanfacine is not dialyzable in clinically significant amounts (2.4%).

Guanfacine hydrochloride tablets are contraindicated in patients with known hypersensitivity to the drug.

Last updated on RxList: 12/6/2007

Guanfacine hydrochloride is an orally active antihypertensive agent whose principal mechanism of action appears to be stimulation of central a2-adrenergic receptors. By stimulating these receptors, guanfacine reduces sympathetic nerve impulses from the vasomotor center to the heart and blood vessels. This results in a decrease in peripheral vascular resistance and a reduction in heart rate.

The dose-response relationship for blood pressure and adverse effects of guanfacine given once a day as monotherapy has been evaluated in patients with mild to moderate hypertension. In this study patients were randomized to placebo or to 0.5 mg, 1 mg, 2 mg, 3 mg, or 5 mg of guanfacine. Results are shown in the following table. A useful effect was not observed overall until doses of 2 mg were reached, although responses in white patients were seen at 1 mg; 24 hour effectiveness of 1 mg to 3 mg doses was documented using 24 hour ambulatory monitoring. While the 5 mg dose added an increment of effectiveness, it caused an unacceptable increase in adverse reactions.

Mean Changes (mm Hg) from Baseline in Seated Systolic and Diastolic Blood Pressure for Patients Completing 4 to 8 Weeks of Treatment with Guanfacine Monotherapy

Mean Change	n=
S/D* Seated	(range)	Placebo	0.5 mg	1 mg	2 mg	3 mg	5 mg
White Patients	11-30	-1/-5	-6/-8	-8/-9	-12/-11	-15/-12	-18/-16
Black Patients	8-28	-3/-5	0/-2	-3/-5	-7/-7	-8/-9	-19/-15
*S/D = Systolic/diastolic blood pressure

Controlled clinical trials in patients with mild to moderate hypertension who were receiving a thiazide-type diuretic have defined the dose-response relationship for blood pressure response and adverse reactions of guanfacine given at bedtime and have shown that the blood pressure response to guanfacine can persist for 24 hours after a single dose. In the 12-week placebo-controlled dose-response study, patients were randomized to placebo or to doses of 0.5, 1, 2, and 3 mg of guanfacine, in addition to 25 mg chlorthalidone, each given at bedtime. The observed mean changes from baseline, tabulated below, indicate the similarity of response for placebo and the 0.5 mg dose. Doses of 1, 2, and 3 mg resulted in decreased blood pressure in the sitting position with no real differences among the three doses. In the standing position there was some increase in response with dose.

Mean Decreases (mm Hg) in Seated and Standing Blood Pressure for Patients Treated with Guanfacine in Combination with Chlorthalidone

		Placebo	0.5 mg	1 mg	2 mg	3 mg
Mean Change	n=	63	63	64	58	59
S/D* Seated		-5/-7	-5/-6	-14/-13	-12/-13	-16/-13
S/D* Standing		-3/-5	-5/-4	-11/-9	-9/-10	-15/-12
*S/D = Systolic/diastolic blood pressure

While most of the effectiveness of guanfacine in combination (and as monotherapy in white patients) was present at 1 mg, adverse reactions at this dose were not clearly distinguishable from those associated with placebo. Adverse reactions were clearly present at 2 and 3 mg (see ADVERSE REACTIONS).

In a second 12-week placebo-controlled study 1, 2, or 3 mg of guanfacine hydrochloride administered with 25 mg chlorthalidone once daily, a significant decrease in blood pressure was maintained for a full 24 hours after dosing. While there was no significant difference between the 12 and 24 hour blood pressure readings, the fall in blood pressure at 24 hours was numerically smaller, suggesting possible escape of blood pressure in some patients and the need for individualization of therapy.

In a double-blind, randomized trial, either guanfacine or clonidine was given at recommended doses with 25 mg chlorthalidone for 24 weeks and then abruptly discontinued. Results showed equal degrees of blood pressure reduction with the two drugs and there was no tendency for blood pressures to increase despite maintenance of the same daily dose of the two drugs. Sign and symptoms of rebound phenomena were infrequent upon discontinuation of either drug. Abrupt withdrawal of clonidine produced a rapid return of diastolic and especially, systolic blood pressure to approximately pretreatment levels, with occasional values significantly greater than baseline, whereas guanfacine withdrawal produced a more gradual increase to pretreatment levels, but also with occasional values significantly greater than baseline.

Pharmacodynamics

Hemodynamic studies in man showed that the decrease in blood pressure observed after single-dose or long-term oral treatment with guanfacine was accompanied by a significant decrease in peripheral resistance and a slight reduction in heart rate (5 beats/min). Cardiac output under conditions of rest or exercise was not altered by guanfacine.

Guanfacine lowered elevated plasma renin activity and plasma catecholamine levels in hypertensive patients, but this does not correlate with individual blood-pressure responses.

Growth hormone secretion was stimulated with single oral doses of 2 and 4 mg of guanfacine. Long-term use of guanfacine had no effect on growth hormone levels.

Guanfacine had no effect on plasma aldosterone. A slight but insignificant decrease in plasma volume occurred after one month of guanfacine therapy. There were no changes in mean body weight or electrolytes.

Pharmacokinetics

Relative to an intravenous dose of 3 mg, the absolute oral bioavailability of guanfacine is about 80%. Peak plasma concentrations occur from 1 to 4 hours with an average of 2.6 hours after single oral doses or at steady state.

The area under the concentration-time curve (AUC) increases linearly with the dose.

In individuals with normal renal function, the average elimination half-life is approximately 17 hr (range 10-30 hr). Younger patients tend to have shorter elimination half-lives (13-14 hr) while older patients tend to have half-lives at the upper end of the range. Steady state blood levels were attained within 4 days in most subjects.

In individuals with normal renal function, guanfacine and its metabolites are excreted primarily in the urine. Approximately 50% (40-75%) of the dose is eliminated in the urine as unchanged drug; the remainder is eliminated mostly as conjugates of metabolites produced by oxidative metabolism of the aromatic ring.

The guanfacine-to-creatinine clearance ratio is greater than 1, which would suggest that tubular secretion of drug occurs.

The drug is approximately 70% bound to plasma proteins, independent of drug concentration.

The whole body volume of distribution is high (a mean of 6.3 L/kg), which suggests a high distribution of drug to the tissues.

The clearance of guanfacine in patients with varying degrees of renal insufficiency is reduced, but plasma levels of drug are only slightly increased compared to patients with normal renal function. When prescribing for patients with renal impairment, the low end of the dosing range should be used. Patients on dialysis also can be given usual doses of guanfacine hydrochloride as the drug is poorly dialyzed.

Last updated on RxList: 12/6/2007

Patients who receive guanfacine should be advised to exercise caution when operating dangerous machinery or driving motor vehicles until it is determined that they do not become drowsy or dizzy from the medication. Patients should be warned that their tolerance for alcohol and other CNS depressants may be diminished. Patients should be advised not to discontinue therapy abruptly.

Last updated on RxList: 12/6/2007

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.

GUANFACINE - ORAL

(GWAN-fuh-seen)

COMMON BRAND NAME(S): Tenex

USES: This medication is used alone or with other medications to treat high blood pressure (hypertension). Lowering high blood pressure helps prevent strokes, heart attacks, and kidney problems. Guanfacine belongs to a class of drugs known as centrally acting antihypertensives. It works by decreasing the levels of certain brain chemicals (neurotransmitters), causing relaxation of blood vessels and decreasing blood pressure.

HOW TO USE: Take this medication by mouth, usually once daily at bedtime or exactly as prescribed by your doctor. You may take this medication with or without food, but it is important to choose one and take the medication that way every time. It is best to take guanfacine at bedtime to decrease side effects during the day.

Dosage is based on your medical condition, tolerance of side effects, and response to treatment. The dose may be increased 3 to 4 weeks after starting this medication if your blood pressure is not lowered enough.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day. It is important to continue taking this medication even if you feel well. Most people with high blood pressure do not feel sick. It may take up to several weeks before the full benefit of this drug takes effect.

Do not stop taking this medication without first consulting your doctor. Some conditions may become worse when the drug is abruptly stopped. Your dose may need to be gradually decreased.

Inform your doctor if your condition worsens (e.g., your routine blood pressure readings increase) or you experience severe side effects.

SIDE EFFECTS: Dry mouth, drowsiness, dizziness, constipation, weakness, headache, and sleeping problems may occur. Less common side effects may include headache, stomach upset, and nausea. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

To relieve dry mouth, suck on (sugarless) hard candy or ice chips, chew (sugarless) gum, drink water, or use a saliva substitute. To help prevent constipation, eat adequate fiber, drink plenty of fluids, and exercise. If constipation occurs, ask your pharmacist for help selecting a laxative.

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: sudden pounding heartbeat, fainting, tingling, leg pain, joint/muscle aches, blurred vision, mental/mood changes (e.g., depression, anxiety, confusion, nervousness), unusually slow heartbeat, decreased sexual ability/interest, shakiness.

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: 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 guanfacine, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: liver problems, kidney problems, severely blocked heart blood vessels (coronary artery disease), severe and returning chest pain (angina), heart attack in the last year, blockage of blood vessels in the brain (cerebrovascular disease).

This drug may cause dizziness or drowsiness. Use caution while driving, using machinery, or doing any activity that requires alertness. Use of alcohol or certain other medications that cause drowsiness could increase these effects (see Drug Interactions section). Limit alcoholic beverages.

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

Caution is advised when using this guanfacine in the elderly because they may be more sensitive to the drowsiness and dizziness effects.

Caution is advised when using this guanfacine in children with a certain behavior problem (attention-deficit hyperactivity disorder-ADHD). Use of guanfacine in some children with this problem has caused unusual changes in behavior (e.g., aggression, mania).

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

It is not known whether this drug passes into breast milk. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: Your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor or pharmacist first.

Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially of: phenobarbital, phenytoin, other blood pressure medications (e.g., beta blockers such as propranolol, diuretics such as hydrochlorothiazide, calcium channel blockers such as nifedipine or amlodipine, ACE inhibitors such as lisinopril, among others).

Before using this medication, tell your doctor or pharmacist if you use any other prescription and nonprescription products that cause drowsiness such as certain antihistamines (e.g., diphenhydramine), anti-seizure drugs (e.g., carbamazepine), medicine for sleep or anxiety (e.g., alprazolam, diazepam, zolpidem), muscle relaxants (e.g., methocarbamol), narcotic pain relievers (e.g., codeine), psychiatric medicines (e.g., chlorpromazine, risperidone, trazodone).

Check the labels on all your medicines (e.g., cough-and-cold products) because they may contain ingredients that can worsen blood pressure control if used with this medication (e.g., phenylephrine, pseudoephedrine). Ask your pharmacist about using those products safely.

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. Canada residents can call a provincial poison control center. Symptoms of overdose may include: severe drowsiness, severe tiredness, unusually slow heartbeat, low blood pressure.

NOTES: Do not share this medication with others.

Lifestyle changes such as stress reduction programs, exercise, and dietary changes may increase the effectiveness of this medicine. Talk to your doctor or pharmacist about lifestyle changes that might benefit you.

Keep all medical appointments so that your doctor can monitor your progress or check for side effects. Consult your doctor for more details.

Have your blood pressure checked regularly while taking this medication. Learn how to monitor your own blood pressure, and share the readings with your doctor.

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.