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Side Effects & Adverse Reactions
Verapamil has a negative inotropic effect which, in most patients, is compensated by its afterload reduction (decreased systemic vascular resistance) properties without a net impairment of ventricular performance. In clinical experience with 4,954 patients, 87 (1.8%) developed congestive heart failure or pulmonary edema. Verapamil should be avoided in patients with severe left ventricular dysfunction (e.g., ejection fraction less than 30%, or moderate to severe symptoms of cardiac failure) and in patients with any degree of ventricular dysfunction if they are receiving a beta adrenergic blocker (see, Drug Interactions). Patients with milder ventricular dysfunction should, if possible, be controlled with optimum doses of digitalis and/or diuretics before verapamil treatment (Note interactions with digoxin under: PRECAUTIONS).
Occasionally, the pharmacologic action of verapamil may produce a decrease in blood pressure below normal levels which may result in dizziness or symptomatic hypotension. The incidence of hypotension observed in 4,954 patients enrolled in clinical trials was 2.5%. In hypertensive patients, decreases in blood pressure below normal are unusual. Tilt table testing (60 degrees) was not able to induce orthostatic hypotension.
Elevated Liver Enzymes
Elevations of transaminases with and without concomitant elevations in alkaline phosphatase and bilirubin have been reported. Such elevations have sometimes been transient and may disappear even in the face of continued verapamil treatment. Several cases of hepatocellular injury related to verapamil have been proven by rechallenge; half of these had clinical symptoms (malaise, fever, and/or right upper quadrant pain) in addition to elevations of SGOT, SGPT and alkaline phosphatase. Periodic monitoring of liver function in patients receiving verapamil is therefore prudent.
Accessory Bypass Tract (Wolff-Parkinson-White or Lown-Ganong-Levine)
Some patients with paroxysmal and/or chronic atrial fibrillation or atrial flutter and a coexisting accessory AV pathway have developed increased antegrade conduction across the accessory pathway bypassing the AV node, producing a very rapid ventricular response or ventricular fibrillation after receiving intravenous verapamil (or digitalis). Although a risk of this occurring with oral verapamil has not been established, such patients receiving oral verapamil may be at risk and its use in these patients is contraindicated (see CONTRAINDICATIONS).
Treatment is usually DC-cardioversion. Cardioversion has been used safely and effectively after oral verapamil HCl.
The effect of verapamil on AV conduction and the SA node may cause asymptomatic first-degree AV block and transient bradycardia, sometimes accompanied by nodal escape rhythms. PR interval prolongation is correlated with verapamil plasma concentrations, especially during the early titration phases of therapy. Higher degrees of AV block, however, were infrequently (0.8%) observed. Marked first-degree block or progressive development to second- or third-degree AV block requires a reduction in dosage or, in rare instances, discontinuation of verapamil HCI and institution of appropriate therapy depending upon the clinical situation.
Patients with Hypertrophic Cardiomyopathy (IHSS)
In 120 patients with hypertrophic cardiomyopathy (most of them refractory or intolerant to propranolol) who received therapy with verapamil at doses up to 720 mg/day, a variety of serious adverse effects were seen. Three patients died in pulmonary edema; all had severe left ventricular outflow obstruction and a past history of left ventricular dysfunction. Eight other patients had pulmonary edema and/or severe hypotension; abnormally high (greater than 20 mmHg) pulmonary wedge pressure and a marked left ventricular outflow obstruction were present in most of these patients. Concomitant administration of quinidine (see, Drug Interactions) preceded the severe hypotension in 3 of the 8 patients (2 of whom developed pulmonary edema). Sinus bradycardia occurred in 11% of the patients, second-degree AV block in 4% and sinus arrest in 2%. It must be appreciated that this group of patients had a serious disease with a high mortality rate. Most adverse effects responded well to dose reduction and only rarely did verapamil have to be discontinued.
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Verapamil Hydrochloride Extended-Release Tablets, USP is indicated for the management of essential hypertension.
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Verapamil hydrochloride is a calcium ion influx inhibitor (slow channel blocker or calcium ion antagonist). Verapamil Hydrochloride Extended-Release Tablets, USP is available for oral administration as light green, capsule shaped, scored, biconvex film-coated tablets containing 240 mg verapamil hydrochloride; pink, oval shaped, scored, biconvex film-coated tablets containing 180 mg verapamil hydrochloride; and light pink, oval shaped, biconvex film-coated tablets, containing 120 mg verapamil hydrochloride. The tablets are designed for sustained-release of the drug in the gastrointestinal tract, sustained-release characteristics are not altered when the tablet is divided in half.
The structural formula of verapamil HCl is given below:
C 27H 38N 2O 4•HCl............. M.W. 491.06
Benzeneacetonitrile, α [3-[[2-(3,4-dimethoxyphenyl) ethyl] methylamino]propyl]-3,4 dimethoxy-α‑-(1-methylethyl) hydrochloride
Verapamil HCl is an almost white, crystalline powder, practically free of odor, with a bitter taste. It is soluble in water, chloroform and methanol. Verapamil HCl is not chemically related to other cardioactive drugs.
In addition to verapamil HCl, the verapamil hydrochloride extended-release tablet contains the following ingredients: sodium alginate, hypromellose, hydroxypropyl cellulose, magnesium stearate, colloidal silicon dioxide, polyethylene glycol, and titanium dioxide. The following are the color additives per tablet strength:
Strength (mg) Color Additive(s)
120 Ferric Oxide Red and Black Iron Oxide
180 Ferric Oxide Orange
240 Indigotine Aluminium Lake 12-14% and D&C Yellow #10 Aluminium Lake
USP Dissolution Test pending.