The US Food and Drug Administration has tightened its dosing rules for women taking a certain type of sleeping pill.
The agency said that at current dose levels, patients taking zolpidem-containing insomnia medicines – including Ambien or Ambien CR, Edluar and Zolpimist – can be left with a high level of the active ingredient in their blood in the morning.
This can impair their ability to drive, as well as other activities that require alertness.
The requirement just covers women, whose bodies eliminate zolpidem more slowly than men, although the FDA also said the drug’s labelling should be updated to recommend healthcare professionals consider a lower dose for men.
Evidence supporting the decision comes from a series of driving simulations and studies that demonstrated about 15 per cent of women and 3 per cent of men had zolpidem concentrations that exceeded a safe range eight hours after they took a 10m dose of Ambien (or a bioequivalent product).
The figures were even higher for the extended release version of Ambien at 12.5mg dose, with about 33 per cent of women and 25 per cent of men left with an unsafe concentration of zolpidem, while for the 6.25mg dose, the respective proportions were 15 per and 5 per cent.
Dr Ellis Unger, a director in the FDA’s Center for Drug Evaluation and Research, explained the reason behind these studies.
“Over the years FDA has received spontaneous adverse event reports of driving impairment and motor vehicle accidents associated with zolpidem, but these reports lacked the information necessary to fully understand whether and how zolpidem affected people’s mental alertness and ability to drive,” she said.
The new FDA requirements now mean the recommended dosage of zolpidem for women is cut from 10mg to 5 mg for immediate-release products, while the recommended dosage for extended-release products is lowered from 12.5mg to 6.25mg.
For men, the FDA said it has informed manufactures of the products that the label should recommend that healthcare professionals consider prescribing these lower doses.
Ambien was originally developed by Sanofi, but is now available in a generic form. Edluar is a sublingual version marketed by Meda Pharmaceuticals and Zolpimist is an oral spray version marketed by NovaDel.