A watch list of 13 drugs based on potential signs of serious risks or new safety information collected by the Adverse Event Reporting System (AERS) of the US Food and Drug Administration (FDA) during the first quarter of 2010 has been released.

The FDA is studying all of the drugs to determine the need for any regulatory action.

A drug’s appearance on the watch list does not mean the agency has determined that the drug poses the health risk in question. Physicians should not stop prescribing the drug, and patients should not stop taking it, according to the FDA.

The FDA is evaluating 2 antibiotics — azithromycin (Zithromax; Pfizer) and clarithromycin (Biaxin; Abbott) — to find out whether they are associated with liver failure. Suspicions about azithromycin and liver failure are not new. The label for the antibiotic states that adverse events discovered after the drug entered the marketplace — and for which a causal relationship may not be established — include “abnormal liver function including hepatitis and cholestatic jaundice, as well as rare cases of hepatic necrosis and hepatic failure, some of which have resulted in death.” During clinical trials, cholestatic jaundice was a rarely reported adverse effect.

Postmarketing adverse events for clarithromycin have included infrequent cases of sometimes severe, but usually reversible, hepatic dysfunction, including cholestatic hepatitis, with or without jaundice. There also have been rare and fatal cases of hepatic failure “associated with serious underlying diseases and/or concomitant medications,” according to the drug label. Cholestatic jaundice did not emerge as an adverse effect in clinical trials.

Two other antibiotics made it on the latest watch list. AERS turned up reports of pyloric stenosis linked to azithromycin extended release 2 g (Zmax; Pfizer) and pulmonary eosinophilia and eosinophilic pneumonia linked to daptomycin (Cubicin; Cubist Pharmaceuticals).

FDA Studying Anticoagulant to Determine Whether It Causes Blood Clots

Three other medications on the watch list are in the cardiovascular camp. The anticoagulant prasugrel (Effient; Eli Lilly), is being watched on account of thrombotic thrombocytopenic purpura — a rare and life-threatening disorder that causes clots to form in small blood vessels throughout the body. The drug’s label warns that this disorder emerged as an adverse effect during clinical trials. Heartwire recently reported that researchers continue to debate whether the medication increases the risk for cancer.

Another drug, dronedarone (Multaq; Sanofi-Aventis), used to treat atrial fibrillation and atrial flutter, has come under surveillance because of reports of congestive heart failure. As reported by Heartwire, clinicians have considered dronedarone a safer alternative to amiodarone (Cordarone; Wyeth-Ayerst; Pacerone; Upsher-Smith) for patients with atrial fibrillation.

The third cardiovascular drug on the watch list is ranolazine (Ranexa; Gilead), prescribed for patients with angina. Here, the FDA is investigating reports of torsades de pointes — a ventricular tachycardia that can lead to sudden death.

Two medications prescribed for narcolepsy — modafinil (Provigil; Cephalon) and sodium oxybate (Xyrem; Jazz Pharmaceuticals) — are under study for a possible association with convulsions. Physicians prescribe modafinil to counteract excessive sleepiness caused by narcolepsy, sleep apnea, or shift work. Likewise, sodium oxybate reduces daytime sleepiness, as well as the number of cataplexy attacks suffered, in patients with narcolepsy.

Perhaps the most well-known product on the watch list is the blend of estrogens marketed as Premarin (Wyeth), used to treat symptoms of menopause. It landed on the list based on reports of angioedema.

Potential Signals of Serious Risks/New Safety Information Identified by AERS, First Quarter 2010

The current list of drugs is available on the FDA Web site.