Pharmacology Update

The Latest Information on New Drugs and New Indications

By William T. Elliott, MD, FACP

Pharmacoeconomics is a concept in search of legitimacy. most pharmacoeconomic studies are funded by the pharmaceutical industry and are often viewed by physicians and formulary committees as no more than marketing ploys. Now, the FDA is stepping in to attempt to regulate marketing based on pharmacoeconomic data by developing guidance regarding promotional claims. The guidelines will attempt to level the playing field. When claims based on pharmacoeconomic studies are made, the FDA wants those claims to be based on valid data. The guidelines are in the process of being drafted (a process that has turned out to be long and arduous), but expect to see them by mid year.

A recent article in JAMA has caused concern for millions of patients on chronic coumadin therapy (Hylek et al. 1998;279:657-662). Generally unable to take non-steroidal anti-inflammatory drugs (NSAIDs) because of their antiplatelet effect, most coumadin patients have turned to acetaminophen for relief of mild pain. Researchers from Harvard have reported that taking four or more regular strength acetaminophen daily for a week dramatically increases the risk of having an INR of greater than 6. It is felt that acetaminophen may affect hepatic metabolism of coumadin. Taking seven or less acetaminophen a week poses no risk of excess anticoagulation.

In the competitive anti-herpes market, acyclovir still dominates the scene, with new generics cutting into Glaxo Wellcome's brand name Zovirax product, but newcomers Valtrex (valacyclovir) and Famvir (famciclovir) are making inroads. Valtrex has now surpassed Famvir in total dollars. Both products represent about 10% of the total $1.3 billion market.

Periurethral injections of collagen have become a popular method of treating stress incontinence in women. Now, researchers from Canada are reporting that 20% of women treated with the injections are at risk of developing complications. The study, published in the Journal of Urology, finds that urgency developed de novo in more than 12% of women after the collagen injections (Stothers L, et al. 1998;159). Other problems included hematuria and urinary retention.

Aspirin may have more benefits than previously thought. The drug's anti-platelet aggregation effect has been thought to be responsible for the benefit in patients with atherosclerosis. Now, researchers have demonstrated that aspirin also improves endothelial function in atherosclerotic arteries. A recent study in Circulation reported that vasodilation of the femoral artery was found to be enhanced after aspirin administration. (Husain S, et al. 1998;97:716-720.)

A new triple therapy kit is available for treating H. pylori. The kit, called Prevpac, contains lansoprazole 30 mg (Prevacid), amoxicillin 1 g, and clarithromycin 500 mg. The patients take one dose twice a day for two weeks. The kit costs approximately $200.

If patients are questioning you about taking folic acid to prevent heart disease, it may not be such a silly question. Taking folic acid has been shown to reduce levels of homocysteine-the amino acid that is under intense scrutiny-and may turn out to be major risk factor for heart disease. Some doctors are using homocysteine levels as a basis for recommending folic acid or other B vitamins such as pyridoxine (B6), much like high cholesterol levels are treated. This may be premature, but taking double or triple the RDA of folic acid (currently set at 200 mcg/d) is probably harmless and may turn out to be of benefit.

Reports of a cure for hepatitis C should be taken with caution, according to U.S. and Canadian physicians. The reports stem from research carried out at Szent Laszlo Hospital in Budapest, Hungary, by Hungarian and American researchers. The researchers claim to have discovered a naturally occuring virus that destroys hepatitis C and leads to cure in the majority of treated patients, although their numbers are small (42 patients tested). Publication of the group's findings will occur within a month.

The hepatitis B vaccine is one of the true medical success stories of the 1990s. Now, Glaxo has penned an agreement with Powderject Pharmaceuticals to jointly develop a hepatitis B vaccine using Powderject's unique delivery system. The system does not involve an injection, but, instead, finely powered drugs triggered by a tiny helium cylinderare are fired at supersonic speeds through the skin. The single-use system is reported to be painless. Glaxo has the option of developing other DNA vaccines using the same system.

Revitalizing a debate that has raged for years, a new article in the Annals of Internal Medicine reexamines the link between cholesterol lowering and violent death and violent behavior (Golomb BA. 1998;128:478-487). The paper postulates that low cholesterol levels may lead to low brain serotonin levels, which may contribute to behavioral changes. This is especially of concern with many recent papers showing the benefits of primary prevention of cardiovascular disease with cholesterol drugs-especially statins.