The U.S. Food and Drug Administration requested black box warnings on fluoroquinolone antibiotics, citing the yet poorly understood risk of tendon rupture. Also, the FDA announced it pushes for black box warnings on epilepsy drugs, claiming they carry a risk of suicidal thoughts and behavior.

Ciprofloxacin is the primary antimicrobial drug targeted by the black box warning, sold by Bayer A.G. under the brand names Cipro, Ciproxin and Ciprobay. It is a broad-spectrum antibiotic which causes double-stranded breaks in the bacterial chromosome and is effective gainst both Gram-positive and Gram-negative bacteria.

Cipro already carries, since 2005 and per FDA request, the warning for tendon ruptures and the development of irreversible neurological conditions. However, the regulator now wants it enclosed in a black box. However, the incidence and severity of side effects is comparatively lower than those triggered by other drugs in its class.

Levofloxacin is also targeted, sold by Ortho-McNeil under the trade name Levaquin and is usually prescribed in respiratory infections. Also, the drug is currently the only respiratory fluoroquinolone approved by the U.S. FDA for the treatment of nosocomial pneumonia. The drug is also targeted by the black box request, as well as Factive (gemifloxacin), Avelox (moxifloxacin), Noroxin (norfloxacin) and Floxin and generic ofloxacin.

Regarding the push for a black box warning on epilepsy drugs, the U.S. Food and Drug Administration underlined the risk of suicide, associated with all drugs used to treat seizures. The FDA found, after analyzing 200 cases, that those taking the drugs face twice the risk of people who are not on anti-epileptic drugs.

However, FDA Director of Neurology Products Russell Katz said that there is no explanation as to why this happens, but reminded there is strong empirical evidence in this direction. Pfizer's Lyrica and GlaxoSmithKline's Lamictal are the drugs most commonly used.

Reuters reports that Pfizer maintains its drug is safe, while Glaxo said the information gathered by the FDA should make it into the drugs' labels. Russell Katz said that at least one company challenges the FDA findings with its own research data, which will be presented to the regulator Thursday.