In the letter from the Food and Drug Administration dated Oct. 11, the agency says BioMarin's Web site "suggests Orapred is safer and more effective than has been demonstrated." According to the agency, the company fails to highlight risks of taking the drug, which is known to cause mood swings and is contraindicated in patients with systemic fungal infections. The Web site also does not mention adverse reactions associated with the drug, which include fluid retention, hypertension, increased appetite and weight gain.

Orapred is primarily used to treat asthma in children because it contains flavor additives to mask the taste of its active ingredient, prednisolone. The drug is also prescribed to control inflammation from other conditions, including types of dermatitis and drug hypersensitivity.

In the warning letter, FDA takes issue with claims that the drug's flavor makes it easier to take. According to the agency, "these claims misleadingly suggests that because of its formulation, patients gag less often when taking Orapred." FDA says there is no documented evidence to support the claim.

BioMarin said Thursday it will comply with FDA by taking the site down immediately. Company spokesman Joshua Grass said BioMarin was surprised by the warning letter because FDA reviewed the content of the site last year and found no problems.

The company entered a North American licensing agreement for Orapred with privately held Alliant Pharmaceuticals in March 2006. In August Biomarin reported receiving a $7.5 million payment from Alliant under the agreement.

Shares of BioMarin Pharmaceutical rose 8 cents Thursday to $16.54 in midday trading on the Nasdaq.