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 replaced by excessive amounts of hypotonic solutions.

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, and doubles the cost.

When two different drops are being used, they should be instilled at least 5 minutes apart.

A transdermal patch formulation of methylphenidate (Daytrana - Noven/Shire) has been approved by the FDA for treatment of attention-deficit/hyperactivity disorder (ADHD) in patients ≥ 6 years old. Like other methylphenidate products, the patch is a schedule II controlled substance. According to the manufacturer, it will be available in pharmacies by the end of June.