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CLORPRES (clonidine hydrochloride and chlorthalidone) ® is generally well tolerated. Most adverse effects are mild and tend to diminish with continued therapy. The most frequent (which appear to be dose-related) are dry mouth, occurring in about 40 of 100 patients; drowsiness, about 33 in 100; dizziness, about 16 in 100; constipation and sedation, each about 10 in 100. In addition to the reactions listed above, certain less frequent adverse experiences, which are shown below, have also been reported
in patients receiving the component drugs of CLORPRES (clonidine hydrochloride and chlorthalidone) ® but in many cases patients were receiving concomitant medication and a causal relationship has not been established:
Gastrointestinal:Nausea and vomiting, about 5 in 100 patients; anorexia and malaise, each about 1 in 100; mild transient abnormalities in liver function tests, about 1 in 100; rare reports of hepatitis; parotitis, rarely.
Metabolic: Weight gain, about 1 in 100 patients; gynecomastia, about 1 in 1000, transient elevation of blood glucose or serum creatine phosphokinase, rarely.
Central Nervous System: Nervousness and agitation, about 3 in 100 patients; mental depression, about 1 in 100; headache, about 1 in 100; insomnia, about 5 in 1000. Vivid dreams or nightmares, other behavioral changes, restlessness, anxiety, visual and auditory hallucinations and delirium have been reported.
Cardiovascular: Orthostatic symptoms, about 3 in 100 patients; palpitations and tachycardia, and bradycardia, each about 5 in 1000. Raynaud's phenomenon, congestive heart failure, and electrocardiographic abnormalities, i.e., conduction disturbances and arrhythmias, have been reported rarely. Rare cases of sinus bradycardia and atrioventricular block have been reported, both with and without the use of concomitant digitalis.
Genitourinary: Decreased sexual activity, impotence and loss of libido, about 3 in 100 patients; nocturia, about 1 in 100; difficulty in micturition, about 2 in 1000; urinary retention, about 1 in 1000.
Other: Weakness, about 10 in 100 patients; fatigue, about 4 in 100; discontinuation syndrome, about 1 in 100; muscle or joint pain, about 6 in 1000 and cramps of the lower limbs, about 3 in 1000. Dryness, burning of the eyes, blurred vision, dryness of the nasal mucosa, pallor, weakly positive Coombs' test, increased sensitivity to alcohol and fever have been reported.
Cardiovascular: Orthostatic hypotension may occur and may be aggravated by alcohol, barbiturates or narcotics.
Whenever adverse reactions are moderate or severe, chlorthalidone dosage should be reduced or therapy withdrawn.
Read the Clorpres (clonidine hydrochloride and chlorthalidone) Side Effects Center for a complete guide to possible side effects
If a patient receiving clonidine hydrochloride is also taking tricyclic antidepressants, the effect of clonidine may be reduced, thus necessitating an increase in dosage. Clonidine hydrochloride may enhance the CNS-depressive effects of alcohol, barbiturates or other sedatives. Amitriptyline in combination with clonidine enhances the manifestation of corneal lesions in rats (see Ocular Toxicity).
In several studies, oral clonidine hydrochloride produced a dose-dependent increase in the incidence and severity of spontaneously occurring retinal degeneration in albino rats treated for six months or longer. Tissue distribution studies in dogs and monkeys revealed that clonidine hydrochloride was concentrated in the choroid of the eye. In view of the retinal degeneration observed in rats, eye examinations were performed in 908 patients prior to the start of clonidine hydrochloride therapy, who were then examined periodically thereafter. In 353 of these 908 patients, examinations were performed for periods of 24 months or longer. Except for some dryness of the eyes, no drug-related abnormal ophthalmologic findings were recorded and clonidine hydrochloride did not alter retinal function as shown by specialized tests such as the electroretinogram and macular dazzle.
In rats, clonidine hydrochloride in combination with amitriptyline produced corneal lesions within 5 days.
Chlorthalidone may add to or potentiate the action of other antihypertensive drugs. Insulin requirements in diabetic patients may be increased, decreased or unchanged. Higher dosage of oral hypoglycemic agents may be required. Chlorthalidone and related drugs may increase the responsiveness to tubocurarine. Chlorthalidone and related drugs may decrease arterial responsiveness to norepinephrine. This diminution is not sufficient to preclude effectiveness of the pressor agent for therapeutic use. Lithium renal clearance is reduced by chlorthalidone, increasing the risk of lithium toxicity.
Drug/Laboratory Test Interactions
Chlorthalidone and related drugs may decrease serum PBI levels without signs of thyroid disturbance.This monograph has been modified to include the generic and brand name in many instances.
Last reviewed on RxList: 5/28/2009
Additional Clorpres Information
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