Adverse effects due to the use of terazosin are mild to moderate.
Terazosin, like other α-blocking agents, can cause syncope (clinical manifestation rate: About 1%). Occasionally, syncopal episodes have been preceded by episodes of severe tachycardia with heart rate of 120-160 beats per minute, but mostly severe orthostatic hypotension may be accompanied. Syncope has been reported within 30-90 min after administering initial dose. It has also been reported in association with rapid dosage increases. If syncope occurs, the patient should be placed in a recumbent position and treated supportively as necessary. Because this adverse reaction is self-controlled, it may not reoccur after administering initial dose or during dosage increases.
In patients exceeding up to 40 mg dose of terazosin, dizziness, energy deficiency and peripheral edema generally occurs. Mostly, this adverse reaction is reduced by sustained therapy or is tolerated without dosage decreases.
Central Nervous System: Depression, hypersensitivity, occasionally headache, dizziness, cenesthopathy, debility, sweating, insomnia, frigidity and shoulder stiffness, rarely drowsiness and numbness may occur.
Circulatory System: Tachycardia, vasodilation, occasionally orthostatic dysregulation, cardiopalmus edema, arrhythmia (extrasystole, atrial fibrillation, etc), cardialgia, rarely cardiagra, tachycardia may occur.
Hepatic: Occasionally, AST, ALT, ALP, total bilirubin increases may occur.
Digestive System: Dyspepsia, abdominal distention, stomach disorder, occasionally abdominalgia, diarrhea, constipation, nausea and vomiting, rarely anorexia may occur.
Respiratory System: Nose bleeding, flu symptom, pharyngitis, rhinitis, dyspnea, cold symptom, nasal hyperemia, cough increase and sinusitis may occur.
Urogenital System: Occasionally oliguria, rarely incontinence (female after menopause), BUN and CPK rise may occur.
Sensory Organ: Paresthesia, balance disturbance, visual disorder, amblyopia, syndesmitis and tinnitus may occur.
Metabolism: Water retention, rarely edema may occur.
Hypersensitivity: Occasionally eruption may occur. If they occur, the administration should be discontinued.
Others: Weight increase, spasticity, arthrocus, arthrorisis asthenia, myalgia, celebitas sexualis, sweating, impotence, priapism and thrombocytopenia, occasionally erethism, stuffed nose, breathless feeling, eye sense of incompatibility and pruritus may occur. Occasionally, antinuclear antibody (ANA) positive may also occur.