MANILA, Philippines - Pills marketed as herbal alternatives to sex-enhancing drugs such as Viagra pose a danger to health, pharmaceutical giant Pfizer warned the public on Tuesday, July 24.

Pfizer senior medical manager Dr James Wee said that herbal pills being sold over-the-counter (OTC) may contain phosphodiesterase type 5 (PDE5) inhibitors or prescription-only Sildenafil drugs, which are used to treat erectile dysfunction.

Wee said many of the pills are produced through substandard processes and may be unsafe.

"PDE5 inhibitors are never bought as OTC medicines. They should only be purchased with a prescription from a physician, thus if you’re buying OTC meds with this compound, then you are putting your life at risk," he added.

Wee gave tips in determining whether a sex-enhancing drug is substandard or counterfeit.

He said counterfeit drugs, in particular, usually do not have generic names, their colors are different from the original and they are "more friable" than the hard original tablets.

"If prints on labels are blurred or hazy and containers look like they have been tampered or recycled, these are usually fake medicines."

"Always look for the DR#, lot#, expiry date, and the logo of the pharmaceutical company. Patients should also ask for official sales invoice of every purchase. Make sure the sales invoice indicates the lot# and expiration date of the drug product," he added. - Rappler.com