GENERIC NAME: clonidine

BRAND NAME: Catapres

DRUG CLASS AND MECHANISM: Clonidine is an oral and topical antihypertensive drug. It also has been used in several other conditions including narcotic and nicotine withdrawal, certain types of vascular headaches, and diarrhea associated with diabetes. Clonidine acts by stimulating adrenergic receptors on nerves in the brain. This stimulation actually reduces messages that originate in the central nervous system (brain) and are transmitted to the body by the sympathetic nervous system. As a result, clonidine slows the heart rate and reduces blood pressure. Clonidine was approved by the FDA in 1974.

PRESCRIPTION: yes

GENERIC AVAILABLE: yes (tablets). No (patches).

PREPARATIONS: Tablets: 0.1mg, 0.2mg, 0.3mg. Transdermal patches releasing 0.1mg, 0.2mg. or 0.3mg over 24 hours.

STORAGE: Tablets and patches should be kept at room temperature, 15-30°C
(59-86°F).

PRESCRIBED FOR: Clonidine is most often prescribed for the treatment of hypertension. It has also been used to manage the symptoms of narcotic withdrawal, nicotine withdrawal, diabetes-associated diarrhea, diabetic neuropathy, hot flashes associated with menopause, and as an adjunct to manage severe cancer-related pain.

DOSING: Clonidine tablets are usually given twice daily. Patches should be applied to an area of hairless skin on the upper arm or torso, once every 7 days. When applying a new patch, a different area of skin should be used.

DRUG INTERACTIONS: Clonidine can increase the sedating effects of other medications that cause sedation. Such drugs include narcotic pain relievers, barbiturates, sedatives such as alprazolam (Xanax) and clonazepam (Klonopin), and ethanol. Tricyclic antidepressants [e.g., amitriptyline (Elavil), imipramine (Tofranil), desipramine (Norpramin), clomipramine (Anafranil)] can block the blood pressure lowering effects of clonidine. This may cause blood pressure to rise.

Since clonidine can reduce the heart rate, it should be used cautiously in persons who are receiving other medications that lower the heart rate such as beta-blockers [e.g., atenolol (Tenormin), metoprolol (Lopressor), propranolol (Inderal)], digoxin (Lanoxin), diltiazem (Cardizem), or verapamil (Calan; Covera HS). Abnormal heart rhythms can occur with the combination of clonidine and verapamil. Cyclosporine (Sandimmune; Neoral) blood concentrations can increase when clonidine is begun. This interaction could result in kidney damage. Nonsteroidal anti- inflammatory drugs [e.g., ibuprofen (Motrin, Advil), naproxen (Naprosyn, Aleve), nabumetone (Relafen)] can reduce the antihypertensive effects of clonidine. Cocaine, pseudoephedrine, phenylephrine, and phenylpropanolamine can reverse the blood pressure lowering effects of clonidine.

PREGNANCY: There is very little information about the effects on the fetus of clonidine given to pregnant women. Clonidine has been used during pregnancy, but reported use during the first trimester is limited. Physicians may use it if its benefits are deemed to outweigh its potential (and unknown) risks.

NURSING MOTHERS: Clonidine is excreted into breast milk. Although clonidine has been found in the blood of nursing newborns whose mothers took clonidine, there are no cases reported of reduced blood pressure in the infants. Nonetheless, since reports are very limited, caution is warranted in treating nursing mothers with clonidine.

SIDE EFFECTS: The most common side effects noted with clonidine are tiredness, lethargy, drowsiness, constipation, and dry mouth. Headache, dizziness, fatigue, and weakness also occur with clonidine. Most persons who experience one of these side effects will usually note that the effects subside with more prolonged therapy or if doses are reduced (approved by the physician). Skin reactions including redness, itching, and darkening of skin, have occurred with clonidine patches.

Sexual dysfunction including impotence, decreased sexual desire, and ejaculatory dysfunction, have been reported with clonidine therapy. Such reactions also have been reported with other medications used to treat hypertension.

Severe rebound high blood pressure can occur following withdrawal from clonidine. This reaction is more likely to occur if clonidine is stopped suddenly (without a gradual dose reduction). Symptoms can include increased salivation, nervousness, headache, heart palpitations, agitation, anxiety, sweating, nausea, muscle pain, and abdominal pain. Slowly reducing the dose of clonidine over several days will prevent this problem.

Last Editorial Review: 5/11/1998

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