Pfizer's Lyrica (pregabalin) is effective in treating restless leg syndrome (RLS) but also less likely than standard therapy with dopamine agonist pramipexole to worsen symptoms of the condition, a study has found.

Research from Massachusetts General Hospital, funded by Pfizer and published in the New England Journal of Medicine, has backed earlier findings that suggest long-term treatment with dopamine agonists - popular treatments for RLS - can actually drive a significant worsening symptoms in some patients.

The year-long study included more than 700 RLS patients and was carried out by more than 100 sites on both sides of the pond. After an initial two-week treatment break, patients were randomised to receive pramipexole, pregabalin or a placebo.

Both groups of patients receiving pregabalin and those taking pramipexole showed a significantly greater symptom improvement compared with the placebo arm.

But, over the 12 months, only 2% of patients receiving pregabalin saw their symptoms worsen versus almost 8% of those on pramipexole 0.5 mg and 5% on the 0.25 mg dose. 

“Our key finding is that dopaminergic drugs, while very effective for many people with RLS, can worsen symptoms in some patients over time, while non-dopaminergic pregabalin is not associated with this disturbing side effect,” said senior study author John Winkelman, Massachusetts General Hospital.

"Probably the most important message for physicians treating patients with RLS is to be aware of the risk of augmentation with dopaminergic drugs, to regularly follow up with patients and not to just increase dosage if symptoms worsen," Winkelman said.

RLS is a neurological disorder characterised by an uncontrollable urge to move the legs that occurs when resting – usually during the evening or at night, interfering with normal sleep and this often leaving affected individuals with chronic exhaustion. Serious RLS affects 2% to 3 % of the US and European populations.  

Lyrica, Pfizer's best-selling drug, is on the market for epilepsy, fibromyalgia and neuropathic pain. But despite not having been approved by the FDA for RLS, the drug is on a number of published treatment guidelines as a first-line treatment option (off-label).