Total US dispensing rates for generic versions of four newly patent-expired drugs reached more than 86% within 30 days of being launched, leading pharmacy benefit manager Medco Health Solutions has reported. And, for its mail-order operations, the generic fill rate for these products averaged 95%, it adds.The biggest-selling drug of the four is Pfizer’s antibiotic Zithromax (azithromycin), whose annual domestic sales exceeded $1.7 billion and rose 19% in third-quarter 2005. Its US patent expired on November 1, 2005, and three generic versions were approved by the US Food and Drug Administration on November 14. Medco reports that the generic dispensing rate for the antibiotic reached more than 90% as of the first week in January, a level which the firm describes as “unprecedented.”The other three products, all made by Sanofi-Aventis, are:
- the anti-allergy drug Allegra (fexofenadine), which had total US sales of $1.4 billion for the 12 months to end-June 2005, according to IMS data. FDA approved the generic version produced by Barr Laboratories in early September 2005;
- Amaryl (glimepiride), indicated to help lower glucose in patients with type 2 diabetes whose hyperglycaemia cannot be controlled by diet and exercise alone. The generic version was approved on October 7 last year, and Prasco, a privately-held drugmaker which began shipping an authorised generic version later that month, estimated that the branded product’s sales had reached $353 million in the previous 12 months, with over 8 million prescriptions filled; and
- Arava (leflunormide), an oral disease-modifying antirheumatic drug used to treat rheumatoid arthritis in adults, whose US sales in 2004 exceeded $175 million. The generic version became available on September 15, 2005.