Generic Paxil Scheduled to Hit Market this Fall
Pharmacology Watch

A generic form of paroxetine (Paxil—GlaxoSmithKline) will soon be on the market. The drug marks the second SSRI antidepressant to go generic after fluoxetine (Prozac) last year. US sales of Paxil reached $2.23 billion last year, and the approval of a generic is a blow to GSK’s bottom-line but is welcome news to consumers. Generic paroxetine will be launched by Canadian drugmaker Apotex almost a year earlier than most analysts had anticipated because of continued legal wrangling over patents. If generic companies launch a drug that is later found in violation of the branded drugs patents, they are liable for treble damages, a threat that has impeded generic competition in the past. In this case, Apotex feels it has a strong legal basis for defending any claims by GSK, a pattern that is being seen more frequently among generic companies in the last year. Generic paroxetine should be available this fall in 4 different dosing strengths.

New Study Questions CHD and C pneumoniae

An association between Chlamydia pneumoniae infection and coronary heart disease has been suggested by several lines of evidence; however, a new, large, multicenter study fails to confirm this association. Nearly 8000 adults with a recent myocardial infarction and positive C pneumoniae titers were randomized to 12 weeks of azithromycin (600 mg/d for 3 days then 600 mg/wk through week 12) or placebo. The primary outcomes were death from any cause, non-fatal reinfarction, coronary revascularization, or hospitalization for angina. After a median of 14 months of follow-up, there was no significant risk reduction with azithromycin vs placebo (any primary event 7% risk reduction with azithromycin, P =.23). Adverse reactions to the study drug occurred in 13.2% of patients randomized to azithromycin and were generally mild—predominately diarrhea. The study represents the largest antibiotic trial to date for the eradication of C pneumoniae, and although there were indications that there might be an early benefit, this was not sustained at 14 weeks. The authors suggest that there’s no justification for the use of antibiotics in treating patients with coronary disease (JAMA. 2003;290:1459-1466).

Warfarin Patients: Limit Cranberry Juice

Cranberry juice may increase the risk of hemorrhage in patients taking warfarin according to British researchers. The British Committee on Safety of Medicines recommended patients taking warfarin should limit or avoid drinking cranberry juice until they can sort out 5 reports of hemorrhage associated with the combination, including 1 death. In all cases, increases in INR were noted when patients who had been stabilized on warfarin started drinking cranberry juice. The committee postulates that the juice inhibits cytochrome P450 activity, thus slowing metabolism of warfarin. Cranberry juice has been touted in recent years for its antioxidant properties as well as its purported ability to prevent or treat urinary tract infections.

Therapeutic Magnets Put to Test

A randomized double-blind trial has finally put therapeutic magnets to the test for the treatment of foot pain. Researchers at the Mayo Clinic randomized 101 adults with the diagnosis of plantar heel pain to treatment with cushioned insoles with bipolar magnets and sham magnets. The insoles were worn daily for 8 weeks. The main outcome was reported average daily for pain and the effect of the insoles on work performance and enjoyment. Again, at 8 weeks no significant difference was noted between the 2 groups, with both groups reporting significant improvements in foot pain (33% improvement nonmagnetic group, 35% improvement magnetic group [P = .78]). The authors conclude that embedded bipolar magnets to add nothing to cushioned insoles and the treatment of plantar heel pain (JAMA. 2003;290:1474-1478).

St. John’s Wort Might Block Certain Medications

St. John’s wort, the popular herbal product that is widely used to self-treat depression may significantly reduce the effectiveness of at least 50% of all marketed medications. A new study looked at the effect of St. John’s wort on cytochrome P450 (CYP) enzymes. Twelve healthy volunteers (6 men and 6 women) were given St. John’s wort for 14 days. Participants were given dextromethorphan and alprazolam before and after administration of St. John’s wort to assess plasma pharmacokinetics. After 14 days use of St. John’s wort, a 2-fold decreased area under the curve for alprazolam plasma concentration and a 2-fold increase in alprazolam clearance was found as well as an elimination half-life that decrease from 12.4 h to 6.0 h suggesting a significantly induced activity of CYP 3A4 (all findings significant at P < .001). Dextromethorphan metabolism, a measure of CYP 2D6, was unchanged. The effect of St. John’s wort on CYP 3A4 is quite significant, however, since at least 50% of all medications currently on the market are at least partially metabolized by this enzyme. This, coupled with 2 recent multicenter double-blind, placebo-controlled studies questioning the effectiveness of St. John’s wort for the treatment of depression, should alert clinicians to question their patients about their use of herbal medications, especially St. John’s wort (JAMA. 2003;290:1500-1504).

Parathyroid Hormone and Alendronate Offer No Improved Osteoporosis Treatment

Parathyroid hormone and alendronate in combination offer no advantage and may in fact be less effective than either drug alone in treating osteoporosis according to 2 studies in the Sept. 25 issue of New England Journal of Medicine. In a study of 83 men with low bone density, 28 were randomized to receive alendronate 10 mg/d, 27 received parathyroid hormone 40 mg subcutaneously daily, while 28 men received both. The bone mineral density of the lumbar spine, proximal femur, radial shaft, and total body was measured every 6 months and trabecular bone mineral density of the lumbar spine was measured at baseline and 30 months. The most effective treatment was parathyroid hormone alone (P < 0.001 for both comparisons), and it appeared that alendronate impaired the ability of parathyroid hormone to increase bone mineral density at the lumbar spine and femoral neck. In the second study, 238 postmenopausal women with low bone mineral density at the hip or spine were randomly assigned to daily treatment with parathyroid hormone 100 mg/d (119 women), alendronate 10 mg/d (60 women), or both (59 women). After 12 months of follow-up, bone mineral density was assessed at the spine and hip. Bone mineral density increased in all treatment groups, but the volumetric density of trabecular bone in his spine increase substantially more in the parathyroid hormone group than either of the other groups. The authors suggest that there is no evidence of synergy between parathyroid hormone and alendronate and there may be evidence that alendronate reduces the anabolic effects of parathyroid hormone in the study group (N Engl J Med. 2003;349:1207-1215, 1216-1226).

FDA Actions

Barr laboratories has received approval to market an extended-cycle birth control pill that cuts the number of a women’s menstrual cycles from 13 to 4 per year. Marketed under the trade name "Seasonale," the product is a 91-day ethinyl estradiol/levonorgestrel oral contraceptive regimen that includes 84 days of active hormones and 7 days of placebo. The new product seems to be as effective as other oral contraceptives; however, the label does note that the longer interval between menstrual periods may allow for unintended pregnancies to go undetected for longer period of time.

This supplement was written by William T. Elliott, MD, FACP, Chair, Formulary Committee, Kaiser Permanente, California Division; Assistant Clinical Professor of Medicine, University of California-San Francisco. Telephone: (404) 262-5517. E-mail: In order to reveal any potential bias in this publication, we disclose that Dr. Elliott reports no consultant, stockholder, speaker’s bureau, research, or other financial relationships with companies having ties to this field of study.