Oral drugs approved to treat men with erectile dysfunction should carry stronger warnings on their labelling about the risk of blindness, according to US consumer group Public Citizen.

The pressure group has filed a Citizen’s Petition with the US Food and Drug Administration asking that all three erectile dysfunction drugs in the phosphodiesterase-5 inhibitor class – Pfizer’s Viagra (sildenafil), Lilly ICOS‚ Cialis (tadalafil) and GlaxoSmithKline/Bayer’s Levitra (vardenafil) - have a ‘black box’ warning added to their label. This type of warning is the strongest at the FDA’s disposal.

A similar warning should be added to Pfizer’s recently introduced pulmonary hypertension drug Revatio, which is also based on sildenafil [[07/06/05b]].

Earlier this year, the manufacturers of the drugs agreed to put information on their labels to draw attention to the risk of vision loss caused by non-arteritic anterior ischaemic optic neuropathy or NAION - a condition where blood flow is blocked to the optic nerve [[11/07/05a]]. But Public Citizen claims the warnings lack prominence and have “ambiguous” wording that lessens their impact.

The agency should establish a registry of patients who take the drugs and develop vision loss, the petition says. Drug companies should be required to send “Dear Doctor” letters to all US physicians about the signs and symptoms of vision loss associated with the erectile dysfunction drugs.