Failure of IV atropine to abolish nasal irritation caused by chlormethiazole infusion in elderly patients undergoing spinal anaesthesia

The pharmacology of chlormethiazole: a potential neuroprotective agent?

Chlormethiazole is a thiazole derivative with a long history of use as a sedative agent. The mode of action of the drug has been partly worked out and has been established with recognition that its mechanism of action involves potentiation of GABA activity, the major intrinsic inhibitory neurotransmitter. Animal models of stroke ranging from rodents to primates have suggested an optimistic role for chlormethiazole in preventing both anatomical and functional deleterious effects of stroke. Phase III clinical trials, therefore, proceeded but unfortunately with very little success. Recently, the animal models have been revisited in an attempt to identify causes for this discrepancy between the results from preclinical and clinical studies. This review studies the pharmacological roots of chlormethiazole from its origin through to its licensed and novel applications. Emphasis is placed on discussing the animal experiments which led to its grooming as a neuroprotective agent and also on the human trials. The review seeks to explain the discrepancies between animal and human studies, which include short survival times of experimental subjects, speed of drug administration and fundamental differences between species. The primate model of stroke perhaps offers the nearest alternative to phase III trials and has recently been used to compare a number of newer neuroprotective agents with greater efficacy than chlormethiazole. In addition, novel approaches involving human neurochemical analyses in vivo are described which may help bridge the gap between animal models and future phase III trials.

Sudden unexpected sneezing during the insertion of peribulbar block under propofol sedation

The author presents a case report where, following propofol sedation for a peribulbar block, sneezing was induced once the local anaesthetic needle was placed in the orbital cavity. The physiology of sneezing is discussed, as well as the pathophysiology of the ACHOO (Autosomal Dominant Compelling Helio-Ophthalmic Outburst) syndrome, an autosomal dominant condition, present in approximately 25% of the population, where sneezing is provoked upon exposure to bright light. It is suggested that the anaesthesia induced by propofol may have sensitized patients with this condition to sneeze, since there appeared to be no other excitatory sequelae which have previously been described with propofol.