Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.
Most adverse effects are mild and tend to diminish with continued therapy. The most frequent (which appear to be dose-related) are dry mouth (40%), drowsiness (33%); dizziness (16%); constipation and sedation (10%, respectively).
The following less frequent adverse experiences have also been reported in patients receiving clonidine hydrochloride tablets, but in many cases patients were receiving concomitant medication and a causal relationship has not been established.
Body as a Whole: Fatigue, headache, pallor, malaise, weakness, and withdrawal syndrome.
Cardiovascular: Bradycardia, congestive heart failure, electrocardiographic abnormalities (i.e., sinus node arrest, junctional bradycardia, high degree AV block and arrhythmias), orthostatic symptoms, palpitations, syncope, and tachycardia.
Central Nervous System: Agitation, anxiety, delirium, hallucinations (including visual and auditory), insomnia, mental depression, behavioral changes, paresthesia, sleep disorder, and vivid dreams or nightmares.
Gastrointestinal: Anorexia, constipation, nausea, and vomiting.
Hematologic: Thrombocytopenia.
Hepatobiliary: Hepatitis and transaminitis.
Hypersensitivity: Angioedema, hives, pruritus, rash, and urticaria.
Metabolic: Transient elevation of blood glucose or serum creatine phosphokinase, and weight gain.
Musculoskeletal: Leg cramps and muscle or joint pain.
Ophthalmological: Accommodation disorder, blurred vision, burning of the eyes, decreased lacrimation, and dryness of eyes.
Renal and Urinary: Difficulty in micturition, nocturia, and urinary retention.
Reproductive System and Breast Disorders: Gynecomastia. erectile dysfunction, and loss of libido.
Vascular: Raynaud’s phenomenon.