Phase II trials of a drug designed to assess how effective it is at treating postherpetic neuralgia (PHN) have been launched.

Valeant Pharmaceuticals revealed that its drug retigabine, which is already being tested as a complementary treatment for partial-onset seizures, is to be examined in a trial of 180 patients who have PHN, a complication of the skin condition shingles.

For ten weeks, 120 patients will receive a daily dose of between 300 mg and 900mg of the drug, with a further 60 receiving a placebo.

In a statement the firm said: "The primary outcome assessment will be the comparison of the average pain intensity over the last seven days of maintenance therapy with retigabine versus placebo."

According to the Mayo Clinic, PHN can cause severe pain to patients, even after they have recovered from the initial outbreak of shingles.

Symptoms can also include itching and sensitivity to temperature.

Global healthcare solutions provider Masters can source drugs currently undergoing clinical trails for people with a unique unmet need through its named patient supply programme.