Florida, USA-based Ranbaxy Pharmaceuticals Inc, a wholly-owned subsidiary of India’s largest pharmaceutical company Ranbaxy Laboratories Ltd, has received final approval from the US Food and Drug Administration to manufacture and market gabapentin in 600mg and 800mg strengths.

The FDA has determined these formulations to be bioequivalent and to have the same therapeutic effect as US drug giant Pfizer’s blockbuster Neurontin, which generates annual sales of around $2.2 billion with tablets the 600mg and 800mg totaling $964 million, according to IMS Health data.

Gabapentin is approved for the management of post-herpetic neuralgia in adults, and as adjunctive therapy in the treatment of partial seizures with and without secondary generalization in patients over 12 years of age with epilepsy and is also indicated as adjunctive therapy in the treatment of partial seizures in paediatric patients age 3 - 12 years.

Jim Meehan, the company’s Vice President of Sales and Marketing, commented: “We will now focus on maximising the value of this formulation to the company that will have a positive impact on our performance for the balance of this year. Ranbaxy will begin shipping this affordable generic alternative immediately.”

Pfizer, the world’s largest pharmaceutical group, has absorbed substantial losses in Neurontin sales and prescription volume since the entry of generic competition, led by the USA’s Ivax Corp in the form of 100mg, 300mg and 400mg dosage strengths in August last year [[19/08/04d]]. The company was hit by a 39% fall in turnover of Neurontin in the fourth quarter of 2004, while revenues tumbled 74% in the first quarter of this year.

The US market for major neuropathic pain treatments is currently estimated to be worth around $741.0 million, according to market research consultant WWMR. Accelerated growth over the past two years in this market has been primarily driven by the US approval of Neurontin’s first neuropathic pain indication, post-herpetic neuralgia. Generic competition to this drug is currently retarding near-term growth of the sector, but this should be countered by neuropathic pain launches of drugs such as Eli Lilly’s Cymbalta (duloxetine) and Pfizer’s Lyrica (pregabalin), spurring an annual rate of 17% through 2014, according to WWMR.