Benzodiazepine Dependence - Mechanism - Cross Tolerance

Benzodiazepines share a similar mechanism of action with various sedative compounds that act by enhancing the GABAA receptor. Cross tolerance means that one drug will alleviate the withdrawal effects of another. It also means that tolerance of one drug will result in tolerance of another similarly-acting drug. Benzodiazepines are often used for this reason to detoxify alcohol-dependent patients and can have life-saving properties in preventing and/or treating severe life-threatening withdrawal syndromes from alcohol, such as delirium tremens. However, although benzodiazepines can be very useful in the acute detoxification of alcoholics, benzodiazepines in themselves act as positive reinforcers in alcoholics, by increasing the desire for alcohol. Low doses of benzodiazepines were found to significantly increase the level of alcohol consumed in alcoholics. Alcoholics dependent on benzodiazepines should not be abruptly withdrawn but be very slowly withdrawn from benzodiazepines, as over-rapid withdrawal is likely to produce severe anxiety or panic, which is well known for being a relapse risk factor in recovering alcoholics.

There is cross tolerance between alcohol, the benzodiazepines, the barbiturates, the nonbenzodiazepine drugs, and corticosteroids, which all act by enhancing the GABAA receptor's function via modulating the chloride ion channel function of the GABAA receptor.

Neuroactive steroids, e.g., progesterone and its active metabolite allopregnanolone, are positive modulators of the GABAA receptor and are cross tolerant with benzodiazepines. The active metabolite of progesterone has been found to enhance the binding of benzodiazepines to the benzodiazepine binding sites on the GABAA receptor. The cross-tolerance between GABAA receptor positive modulators occurs because of the similar mechanism of action and the subunit changes that occur from chronic use from one or more of these compounds in expressed receptor isoforms. Abrupt withdrawal from any of these compounds, e.g., barbiturates, benzodiazepines, alcohol, corticosteroids, neuroactive steroids, and nonbenzodiazepines, precipitate similar withdrawal effects characterized by central nervous system hyper-excitability, resulting in symptoms such as increased seizure susceptibility and anxiety. While many of the neuroactive steroids do not produce full tolerance to their therapeutic effects, cross-tolerance to benzodiazepines still occurs as had been demonstrated between the neuroactive steroid ganaxolone and diazepam. Alterations of levels of neuroactive steroids in the body during the menstrual cycle, menopause, pregnancy, and stressful circumstances can lead to a reduction in the effectiveness of benzodiazepines and a reduced therapeutic effect. During withdrawal of neuroactive steroids, benzodiazepines become less effective.

Read more about this topic:  Benzodiazepine Dependence, Mechanism

Famous quotes containing the words tolerance and/or cross:

    For all the injustices in our past and our present, we have to believe that in the free exchange of ideas, justice will prevail over injustice, tolerance over intolerance and progress over reaction.
    Hillary Rodham Clinton (b. 1947)

    In Russia there is an emigration of intelligence: émigrés cross the frontier in order to read and to write good books. But in doing so they contribute to making their fatherland, abandoned by spirit, into the gaping jaws of Asia that would like to swallow our little Europe.
    Friedrich Nietzsche (1844–1900)