Pharmacokinetics
After oral administration of loprazolam on an empty stomach, it takes 2 hours for serum concentration levels to peak, significantly longer than other benzodiazepine hypnotics. This delay brings into question the benefit of loprazolam for the treatment of insomnia when compared to other hypnotics, although some studies show that loprazolam may induce sleep within half an hour, indicating rapid penetration into the brain. The peak plasma delay of loprazolam, therefore, may not be relevant to loprazolam's efficacy as a hypnotic. If taken after a meal it can take even longer for loprazolam plasma levels to peak. Loprazolam significantly alters electrical activity in the brain as measured by EEG, with these changes become more pronounced as the dose increases. Roughly half of each dose is metabolized in humans to produce an active metabolite with similar potency to loprazolam, the other half is excreted unchanged. The half-life of the active metabolite is about the same as the parent compound loprazolam.
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