Among the benzodiazepine tranquillisers, lorazepam – marketed in the UK under the trade names Ativan and Almazine – has acquired a particularly bad public reputation for causing drug dependence and withdrawal symptoms.(1,2) Clear scientific evidence is lacking, but clinical impressions in general support lorazepam's bad press,(3,4) and in a recent study, 20 out of 50 patients consecutively referred for help with benzodiazepine withdrawal were receiving lorazepam.(5)
Why does lorazepam seem to cause greater problems than other benzodiazepines? There are several reasons:
Lorazepam is extremely potent: its anxiety-relieving activity per milligram is estimated to be up to 10 times that of diazepam [Valium].(6) A patient taking what appears to he a small to moderate dose of lorazepam (typically 1mg three or four times a day) may actually be taking the equivalent of 30-40mg diazepam, a very considerable dose. The high potency of lorazepam has not been fully appreciated by medical practitioners. It is thought to result from the especially high affinity of this drug for benzodiazepine receptors in the brain, coupled with a slow rate of disassociation after binding to these receptors.(7) Other potent benzodiazepines, such as triazolam and alprazolam, give rise to similar withdrawal problems.