Conivaptan hydrochloride (Vaprisol - Astellas), a vasopressin antagonist, has been approved by the FDA for short-term intravenous (IV) treatment of euvolemic hyponatremia in hospitalized patients. Euvolemic hyponatremia is most often caused by the syndrome of inappropriate ADH secretion (SIADH), or by hypothyroidism or adrenal insufficiency. The drug has not been approved for treatment of hypervolemic hyponatremia, which is associated with congestive heart failure (CHF), cirrhosis and renal disease. It should not be used in hypovolemic hyponatremia, such as occurs when fluid losses are...

The FDA has approved the marketing of tolvaptan (Samsca - Otsuka), an oral vasopressin receptor antagonist, for treatment of hypervolemic or euvolemic hyponatremia due to congestive heart failure (CHF), cirrhosis or the syndrome of inappropriate antidiuretic hormone secretion (SIADH). A similar drug, conivaptan (Vaprisol) is already available for intravenous (IV) treatment of euvolemic hyponatremia in hospitalized patients. Tolvaptan was approved by the FDA for both inpatient and outpatient use, but it should be started in a hospital.

The FDA has announced changes in the labeling of simvastatin to reduce the risk of myopathy. These changes include limiting the use of the 80-mg maximum dose to patients who have been taking it for 12 months or more without evidence of myopathy and new recommendations for use of simvastatin with other drugs. Simvastatin is available alone (Zocor, and others) and in combination with ezetimibe (Vytorin) and with niacin (Simcor).

Many prescriptions for eye drops call for instillation of 1-2 drops. But Medical Letter consultants in ophthalmology seem to agree that all eye drops should generally be given in doses of only one drop. The volume of a single drop can vary with the viscosity of the solution, the design of the dropper, and patient technique. The average volume of a drop is 35-50 microliters, but can be as high as 75 microliters. An eye brimming with fluid holds 30 microliters at best, so even one drop is often an overdose. A second either washes out the first or increases the possibility of systemic toxicity,...

A recent letter to the editor of the Annals of Internal Medicine documented a single case of myopathy apparently due to an interaction between simvastatin (Zocor, and others) and green tea. Since it became available generically, simvastatin has surpassed atorvastatin (Lipitor) as the best selling statin. As such, it is probably the most common cause of statin-induced myopathy, which is often a result of drug interactions.