Pharmacology Update

The Latest Information on New Drugs and New Indications

Editor's Note: Due to favorable response, the Pharmacology Update column will appear on the cover page of each issue and bring you the latest breaking news from the pharmaceutical industry and clinical pharmacy issues. These updates will include reports of new medications, new indications for medications, adverse drug reactions, and updates on prescribing guidelines. Many of these issues will be expanded upon in future issues of PTDA, but the intent of this column is to report new developments as they are happening.

By William T. Elliott, MD, FACP

Treating hiv is becoming more of a specialty as treatment regimens become more complicated. Now, a group of Dutch researchers are suggesting that combination therapy with four or five antiretrovirals may be more effective in rapidly decreasing HIV RNA than standard therapy with three drugs. It is postulated that rapid decrease in viral load acheived with four or five drugs is important because it reduces the risk of resistant strains or viral "sanctuaries." The Dutch study was presented at the 5th Conference on Retrovirues and Opportunistic Infections in New York.

1997 was a banner year for the pharmaceutical industry. Overall, drug prices increased by 2.5% for the year, and prices for the top selling drugs rose more than 3% for the year. The top selling drugs in 1997 were Prilosec, Prozac, Zocor, Epogen, Zoloft, Paxil, Lipitor, Norvasc, Augmentin, Imitrex, and Claritin.

The CDC has issued new STD treatment guidelines (Morb Mort Wkly Rep MMWR 1998;47[RR-1]). Several single-dose regimens are recommended for the treatment of uncomplicated gonococcal infections. For infections of the cervix, urethra, or rectum, the regimens include cefixime 400 mg orally once, ciprofloxacin 500 mg orally once, ofloxacin 400 mg orally once, or ceftriaxone 125 mg IM once. The ceftriaxone, ciprofloxacin, and ofloxacin regimens are also effective for infections of the pharynx. The CDC also recommends coverage for chlamydial infections with these regimens, either azithromycin 1 g orally once or doxyclycline 100 mg bid for seven days. The azithromycin single-dose treatment along with single-dose gonococcal coverage allows for effective single-dose treatment while the patient is in the clinic. The CDC's guidelines also cover the treatment of herpes simplex infections, genital warts, bacterial vaginosis, scabies, and treating possible STDs associated with sexual assault.

Glaxo has received approval to market a new, long-acting triptan for the treatment of migraine headache. Naratriptan (Amerge) will compete with Glaxo's other anti-migraine product sumatriptan (Imitrex) and Zeneca's new triptan zolmitriptan (Zomig). Naratriptan has a longer duration of action-up to 24 hours-but may take several hours to reach it's peak effect.

Two nasal sprays are now available for the treatment of acute migraine headache; one is a triptan, while the other is an ergot compound. Sumatriptan nasal spray (Imitrex Nasal Spray) begins working as early as 15 minutes after dosing. Dihydroergotamine mesylate (Migranal Nasal Spray) also works quickly-often within 30 minutes-and has a 70% response rate within 23 hours. Both need to be used with caution or avoided in patients with vasospastic conditions or ischemic heart disease.

A new fibrate has been introduced. Fenofibrate (Tricor, Abbott) is indicated for the treatment of hyper-triglyceridemia, especially those who are at risk for pancreatitis. The drug should be available in the next few months.

The anti-leukotriene drug, zafirlukast (Accolate, Zeneca), has received widespread use since it's introduction nearly two years ago. The drug is particularly effective in reducing the need for corticosteroids in steroid dependent asthmatics. A recent report in JAMA (Wechsler ME, et al. JAMA 1998;279(6):455-457) describes a syndrome of pulmonary infiltrates, esosinophilia, and cardiomyopathy similar to Churg-Strauss syndrome in asthmatic patients on zafirlukast. The syndrome was described in eight patients, all of whom had been on chronic steroid therapy, and had reduced or discontinued their steroids when therapy with zafirulkast was initiated. It is unclear whether it is the drug, the steroid withdrawal, or a combination of both that triggers the syndrome. The patients improved dramatically with a discontinuation of the drug and reinitiation of steroids or cyclophosphamide.

The FDA has issued a safety warning about the use of astemizole (Hismanal, Janssen) concomitantly with a long list of other medications and grapefruit juice. Astemizole has carried warnings regarding life-threatening ventricular arrhythmias similar to the warnings given to terfenadine (Seldane) prior to its withdrawal from the market. The FDA has long warned about using astemizole with certain antibiotics and antifungals, but the warnings now recommend against use with clarithromycin, troleandomycin, mibefradil, all the SSRIs (fuloxetine, fluvoxamine, nefazadone, paroxetine, and sertraline), protease inhibitors (ritonavir, indinavir, saquinavir, nelfinavir), and zileuton. Janssen is working with Sepracor, the same company that developed fexofenadine (Allegra) to replace Hoechst's terfenadine (Seldane), to develop a non-cardiotoxic metabolite of astemizole-norastemizole. (See Table for a complete list of commonly used antihistamines and their therapeutic profiles.)