The Medicines and Healthcare products Regulatory Agency has approved the first anti-seizure medication in the UK for patients with a rare epileptic seizure disorder.

Ganaxolone (Ztalmy) treats cyclin-dependent kinase-like 5 (CDKL5) deficiency disorder (CDD) which affects about one in 42,000 people in the country and is caused by mutations in the CDKL5 gene.

The disorder, which can cause seizures from as early as the first week of life, can impact brain function, movement, speech and sight.

Ganaxolone is administered orally through a dosing syringe and the MHRA said prescribing doctors or pharmacists should advise patients about the number of doses they should take.

The regulator said its approval was “supported by evidence” taken from a phase 3 randomised, double-blind, placebo-controlled clinical trial involving 101 patients with CDD aged two to 19 years.

As part of the trial, 51 patients were given the placebo and the other 50 received ganaxolone for 17 weeks. The MHRA said there “was a statistically significant difference in 28-day seizure frequency between the two groups” after 13 weeks.

“Patients receiving ganaxolone saw an average reduction in seizure frequency of almost 30 per cent, while those receiving the placebo had a reduction of almost 6.5 per cent,” it said, adding that ganaxolone’s most common side effects include drowsiness or sleepiness and fever which affects more than one in 10 people.

Julian Beach, the MHRA’s interim executive director, healthcare quality and access, said: “Keeping patients safe and enabling their access to high quality, safe and effective medical products are key priorities for us.

“We’re assured that the appropriate regulatory standards for the approval of this medicine have been met. As with all medicines, we will keep its safety under close review.”