The most common side effect of<unk>  is constipation (7.3%). While the definite mechanism by which<unk>  causes constipation has not been studied, studies have been conducted to rule out mechanisms of actions that might yield this adverse effect. In a study conducted by The National Library of Medicine titled, "Effect of<unk>  on the Human Intestinal Transit", the study found that<unk>  does not have an effect on upper GI transit but rather in the colon. Other side effects include dizziness (3.3%), nausea (2.7%), low blood pressure (2.5%), and headache 2.2%. Other side effects seen in less than 2% of the population include: edema, congestive heart failure, pulmonary edema, fatigue, elevated liver enzymes, shortness of breath, low heart rate, atrioventricular block, rash and flushing. Along with other calcium channel blockers,<unk>  is known to induce gingival enlargement. Overdose Acute overdose is often manifested by nausea, weakness, slow heart rate, dizziness, low blood pressure, and abnormal heart rhythms. Plasma, serum, or blood concentrations of<unk>  and norverapamil, its major active metabolite, may be measured to confirm a diagnosis of poisoning in hospitalized patients or to aid in the medicolegal investigation of fatalities. Blood or plasma<unk>  concentrations are usually in a range of 50–500 μg/L in persons on therapy with the drug, but may rise to 1–4 mg/L in acute overdose patients and are often at levels of 5–10 mg/L in fatal poisonings.
Verapamil
Amiodarone
Flecainide
Sotalol
Procainamide
Tocainide
Acecainide
Ibutilide