A large family of drugs which are very widely used in man as sedatives and anxiolytics, they are not good sedatives in domestic animals but potentiate other drugs. When given alone, they sometimes cause paradoxical excitement - probably by making the animal forget it is supposed to be tame! Many also have active metabolites.
The short acting water soluble drug midazolam is useful as an intravenous premed, although it will not induce anaesthesia on its own in most animals (as it will in man). The most widely used drug is diazepam. It has a medium duration of action in most species (about 20 minutes) although active metabolites may prolong this, especially in combination with other sedatives. Brotizolam has recently be licensed as an appetite stimulant for cattle.
Bind to GABAA receptors and potentiate chloride conductance - hyperpolarise neurones. This can cause generalised reduction in neuronal activity (sedation), or at lower doses can reduce activity in specific pathways, eg, the tonic inhibitory pathway from the ventromedial hypothalamus to the appetite centre in the lateral hypothalamus.
sedative in ruminants, only sedative in combination with other drugs in other species
anticonvulsant
appetite stimulant - useful in cats and possible cattle
anxiolytic?
These are useful emergency drugs as they do not depress the cardiovascular or respiratory systems at normal doses.
emergency treatment for convulsions
potentiate anaesthesia
stimulate appetite in cats & cattle
sedation in shocked animals
An antagonist, flumazenil, is available but too expensive to use.
As a pharmacological curiosity, benzodiazepine inverse agonists (eg β carboline) also exist. These bind to the receptor but produce the opposite effects to an agonist such as diazepam, ie, excitement and anxiety. They are not used clinically!
There is also a plethora of benzodiazepine like drugs on the human market, usually used as sleeping tablets (eg zopiclone). Most of these have not been used in domestic animals but you may sometimes see animals which have eaten their owners’ sleeping pills!
