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The effects of metabolic enzyme induction by rifampin on the pharmacokinetics of tocainide were studied in eight healthy volunteers. In an open, unrandomized fashion, volunteers received tocainide hydrochloride 600 mg orally. Blood samples were obtained immediately before and at various time intervals up to 48 hours after the dose. Urine samples were collected before and at various intervals up to 72 hours after the dose. Serum and urine samples were assayed for tocainide content by high-performance liquid chromatography. After a four-week washout period, volunteers ingested 300 mg of rifampin by mouth every 12 hours. After 10 doses, subjects received a second oral dose of tocainide hydrochloride 600 mg, and blood and urine samples were collected as before. During the sampling period, subjects continued to ingest rifampin 300 mg orally every 12 hours. Significant differences in elimination rate constant (average increase, 0.0545 to 0.0748 hr-1), elimination half-life (average reduction, 13.2 to 9.4 hours), oral clearance, and area under the concentration-time curve (average reduction, 76.8 to 55.0 mg.hr/L) between the control and rifampin treatment phases were observed. Volume of distribution and renal clearance of tocainide were not significantly different after rifampin treatment. Tocainide appears to be susceptible to significant drug-drug interactions mediated by metabolic enzyme induction.

The pathophysiology and treatment of esophageal varices are reviewed. The cause of esophageal varices is generally thought to be portal hypertension. The most common cause of portal hypertension in the United States is alcoholic liver disease. Other etiologies of portal hypertension include portal vein thrombosis, schistosomiasis, and inferior vena caval obstruction by tumor or thrombus. Although short-term balloon tamponade and vasopressin infusion will control acute variceal hemorrhage, they do not affect the underlying problem and are not indicated for long-term treatment of esophageal varices. Surgical procedures either ablate varices or lower portal vein pressure. Portal-systemic shunts have emerged as the preferred surgical technique, but the superiority of total versus selective shunts is unclear. Pharmacological management can include administration of vasopressin, somatostatin, verapamil, or isosorbide dinitrate for short-term treatment or verapamil, isosorbide dinitrate, or propranolol for prolonged treatment. Use of sclerotherapy for treatment and prevention of hemorrhage from esophageal varices has grown recently. Because there are several sclerosing agents and combinations of agents available for use, assessing their relative safety and efficacy is difficult. Innovative approaches to management of varices include a shunt procedure involving the left lung, use of a tissue adhesive, and laser treatment. Because of its effectiveness and ease of administration, sclerotherapy appears to be a rational method of treatment for acute hemorrhage from esophageal varices.