GSK revamps blockbuster migraine drug
GlaxoSmithKline claims to have significantly improved its migraine
treatment Imitrex (sumatriptan) with a new formulation that
dissolves rapidly in the stomach.
The new version of the product is designed to overcome a problem called gastric stasis, which often accompanies a migraine attack. This is a slowing down of the passage of material through the stomach which can impair the absorption of migraine drugs, and delay the onset of pain relief.
The rapid-release technology used in the new version of Imitrex works differently from oral disintegrating tablets, also known as oral melts, which dissolve on the tongue. The new tablets are swallowed whole with water like conventional tablets and dissolve within minutes.
"In an in vitro study, the new tablet dissolved five times faster than conventional tablets, which may allow the drug to be absorbed into the blood stream quickly, said the company, although it stressed that further studies are needed to establish the relationship between dissolution and efficacy.
Previous studies with the original Imitrex tablets showed that 57 per cent of patients who treated with 100 mg tablets in the mild pain phase - and 50 per cent with 50 mg - were pain-free at two hours. A study of the new formulation showed that pain-free rates were 66 per cent with the 100 mg dose and 51 per cent with 50 mg.
The 432-patient study looked at how patients handled a single migraine attack, and those enrolled were given explicit instructions on how to dose themselves. Aside from taking the dose in the mild pain phase, they were told to take Imitrex within one hour of the onset of pain and to avoid the use of other medications.
If only the 313 patients who fully complied with the instructions were evaluated, the pain-free rate improved to 75 per cent for the 100 mg dose at two hours, and 53 per cent for the 50 mg dose.
Imitrex is one of GSK's top products, with sales in excess of $1.2 billion in 2002. The product is scheduled to lose patent protection in the European Union in 2006, followed by the US in 2008, and the new formulation could provide some means of extending the lifespan of the franchise.
Migraines, which can last anything from a couple of hours to two days, occur in about 10 per cent of the adult population, although they are about three times more common in women than in men.
About 74 million people are estimated to be affected by the disease in the world's top seven pharmaceutical markets, according to a recent report published by Decision Resources.