The FDA has announced that it is requiring changes in the labeling of the macrolide antibiotic azithromycin (Zithromax, Zmax) to warn about the risk of QT prolongation and cardiac arrhythmias.1 The new warnings are based on a retrospective study in The New England Journal of Medicine (reviewed previously in The Medical Letter2), which found that among patients who received 347,795 prescriptions for azithromycin, there were 29 cardiovascular deaths, a significantly higher rate than the 42 that occurred among patients who received 1,348,672 prescriptions for amoxicillin (which does not prolong...

Astemizole (Hismanal - Janssen), a new antihistamine, was recently marketed in the USA for treatment of seasonal allergic rhinitis and chronic idiopathic urticaria. Like terfenadine (Seldane - Medical Letter, 27:65, 1985), astemizole is claimed to be no more sedating than placebo, but the new drug offers the advantage of a once-daily dosage schedule.

Carteolol (Cartrol - Abbott) and penbutolol (Levatol - Reed & Carnrick), two oral beta-adrenergic blocking drugs, were recently approved by the US Food and Drug Administration for once-daily treatment of systemic hypertension. Both drugs are non-selective beta-blockers with mild partial agonist activity. Beta-blockers currently available in the USA for treatment of hypertension are listed in the table on the next page.

Advertisements for clemastine (Tavist-1 - Sandoz), an ethanolamine oral antihistamine, have recently appeared on television and in major newspapers in the USA. Clemastine is an old drug (Medical Letter, 21:24, 1979) that has now become available without a prescription.

Acute toxic reactions to drugs of abuse continue to be important problems. Some patients may have mixed intoxications with complex combinations of signs and symptoms.

Paliperidone (Invega - Janssen) has been approved by the FDA in an extended-release formulation for treatment of schizophrenia. It is the primary active metabolite of the second-generation antipsychotic risperidone (Risperdal - Janssen), which is scheduled to lose its patent exclusivity in December 2007.

The US Food and Drug Administration recently approved the marketing of ioversol (Optiray - Mallinckrodt), a new iodinated, low-osmolality, non-ionic X-ray contrast agent. Low-osmolality contrast agents are much more expensive, but they provide as good diagnostic quality as older, high-osmolality contrast media and are claimed to be both better tolerated and safer (Medical Letter, 29:43, 1987).

The FDA has warned that prolonged use of a proton pump inhibitor (PPI) can lead to hypomagnesemia.1 Normal serum concentrations of magnesium are 0.7-1.0 mmol/L. About 30 cases of severe hypomagnesemia (<0.5 mmol/L) have been reported in long-term PPI users; when the PPI was stopped, serum magnesium levels returned to normal in less than 2 weeks.2-5 The exact mechanism is unknown, but in some patients PPIs apparently interfere with active transport of magnesium across the intestinal wall or cause excessive loss into the intestinal lumen.6 Hypomagnesemia is often accompanied by hypocalcemia...

The FDA recently warned that accidental ingestion of the antitussive benzonatate (Tessalon Perles, and others) by children less than 10 years old can be fatal.1 This widely prescribed oral agent, which has been available in the US since 1958, can also cause severe morbidity and death in older children and adults, and not only in overdosage.Benzonatate is a polyglycol derivative structurally related to procaine and tetracaine. It acts peripherally on stretch receptors in the lower respiratory tract to suppress the cough reflex. If the patient chews or sucks the liquid-filled capsules or...

The FDA has approved an IV formulation of the antifungal drug posaconazole (Noxafil - Merck) for prophylaxis of Aspergillus and Candida infections in adults at high risk for these infections, such as those with prolonged neutropenia. Posaconazole is also available as delayed-release tablets and an oral suspension.With activity against Aspergillus and Candida, posaconazole has an antifungal spectrum similar to that of voriconazole (Vfend, and generics), but unlike voriconazole it is also active against many species of Mucorales (formerly called Zygomycetes), such as Mucor and Rhizopus....