Our article on Antiviral Drugs for Prophylaxis and Treatment of Influenza (Med Lett Drugs Ther 2005;47:93) mentioned possible use of amantadine (Symmetrel, and others) and rimantadine (Flumadine, and others), but warned that the incidence of resistance has increased substantially. The CDC recently issued a Health Alert (www.cdc.gov) saying that current evidence indicates that a high proportion of circulating influenza A viruses in the US are now resistant to amantadine and rimantadine and they should not be used for this indication, at least this year. Click here to go to this update...

Rimantadine hydrochloride (Flumadine - Forest), the alpha-methyl derivative of amantadine (Symmetrel, and others), was recently approved by the US Food and Drug Administration for prevention and treatment of influenza A virus infections in adults and for prevention of influenza in children.

Bupropion hydrochloride, currently available as an antidepressant (Wellbutrin - Medical Letter, 31:97, 1989; Wellbutrin SR), is now being marketed in a sustainedrelease formulation as Zyban (Glaxo Wellcome) for use as an aid in smoking cessation.

Zanamivir, a neuraminidase inhibitor taken by inhalation, has been approved by the FDA for treatment of influenza. Oseltamivir phosphate, an oral neuraminidase inhibitor, will probably be approved soon.

The physiologic changes that occur with aging can affect the pharmacokinetics and pharmacodynamics of many prescription and over-the-counter drugs, increasing the likelihood of adverse effects.

Since publication of our recent article on antiviral drugs for influenza, increased levels of resistance to oseltamivir (Tamiflu) have been detected in influenza A H1N1 strains.

FluMist (MedImmune), the first live-attenuated and first intranasally administered influenza vaccine, has been approved by the FDA to prevent influenza in healthy people 5-49 years old. Given as a nasal spray, it stimulates immunity by viral replication in the upper respiratory tract. This vaccine apparently will be advertised directly to the public as a "needle-free" alternative to intramuscular influenza vaccine.

Tetrabenazine (Xenazine - Ovation Pharmaceuticals), an old drug first synthesized 50 years ago for treatment of schizophrenia, was recently approved by the FDA for the treatment of chorea associated with Huntington's disease. It has been available in other countries for decades.

The enzyme alpha-galactosidase (Beano - AkPharma), derived from a mold and classified as a food, is sold without presecription in pharmacies and food stores. The manufacturer recommends taking the anzyme to decrease intestinal gas producted by eating the high-fiber diets now widely recommended in the USA.

As the weather becomes warmer, physicians may see more photosensitivity reactions due to systemic or topical drugs, perfumes, cosmetics or sunscreens. Even brief exposure to sunlight in warm or cold weather can cause intense cutaneous reactions in patients with drug-induced photosensitivity, and some patients may continue to be sensitive to sunlight long after stopping use of the offending agent.