Toxicity of benzodiazepines

Buckley NA, McManus PR (2002) Fatal toxicity of serotoninergic and other antidepressant drugs analysis of United Kingdom mortality data. BMJ 325 1332-1333 Buckley NA, Dawson AH, Whyte IM, O Connell DL (1995) Relative toxicity of benzodiazepines in overdose. BMJ 310 219-221... 

Although rare, benzodiazepine toxicity may occur from an overdose of the drug. Benzodiazepine toxicity causes sedation, respiratory depression, and coma. Flumazenil (Romazicon) is an antidote (antagonist) for benzodiazepine toxicity and acts to reverse die sedation, respiratory depression, and coma within 6 to 10 minutes after intravenous administration. The dosage is individualized based on the patient s response, widi most patients responding to doses of 0.6 to 1 mg. However, die drug s action is short, and additional doses may be needed. Adverse reactions of flumazenil include agitation, confusion, seizures, and in some cases, symptoms of benzodiazepine withdrawal. Adverse reactions of flumazenil related to the symptoms of benzodiazepine withdrawal are relieved by die administration of die benzodiazepine. 

Anxiety disorders are common in the population of opioid-addicted individuals however, treatment studies are lacking. It is uncertain whether the frequency of anxiety disorders contributes to high rates of illicit use of benzodiazepines, which is common in methadone maintenance programs (Ross and Darke 2000). Increased toxicity has been observed when benzodiazepines are co-administered with some opioids (Borron et al. 2002 Caplehorn and Drummer 2002). Although there is an interesting report of clonazepam maintenance treatment for methadone maintenance patients who abuse benzodiazepines, further studies are needed (Bleich et al. 2002). Unfortunately, buspirone, which has low abuse liability, was not effective in an anxiety treatment study in opioid-dependent subjects (McRae et al. 2004). Current clinical practice is to prescribe SSRIs or other antidepressants that have antianxiety actions for these patients. Carefully controlled benzodiazepine prescribing is advocated by some practitioners. 

There have been no formal studies of the toxicity of passionflower, but adverse effects have not been reported. There is one report of a case of inflammatory vasculitis associated with a preparation of passionflower (Smith et al. 1993). Like other herbs in this category, its putative benzodiazepine action contraindicates its combined use with other CNS depressants. 

Since GABA-ergic synapses are confined to neural tissues, specific inhibition of central nervous functions can be achieved for instance, there is little change in blood pressure, heart rate, and body temperature. The therapeutic index of benzodiazepines, calculated with reference to the toxic dose producing respiratory depression, is greater than 100 and thus exceeds that of barbiturates and other sedative-hypnotics by more than tenfold. Benzodiazepine intoxication can be treated with a specific antidote (see below). 

Zopiclone is a chiral cyclopyrrolone with hypnotic properties, possessing a pharmaceutical profile of high efficacy and low toxicity, similar to that of benzodiazepines. Zopiclone has been commercialized as a racemic mixture however, the (S)-enantiomer is more active and less toxic than the (R)-enantiomer [11]. Although enzymatic hydrolysis of esters or transesteriflcation processes of alcohols have been widely applied for enzymatic resolution or desymmetrization... 

Toxic effects, such as seizures and arrhythmias, of other drugs taken in overdose, especially tricyclic antidepressants, may emerge with reversal of sedative effect of benzodiazepines,... 

Ashton, H. (1995). Toxicity and adverse consequences of benzodiazepine use. Psychiatric Annals, 25, 158-165. 

The role of benzodiazepines in brain damage has been reviewed (SEDA-14, 36). Cognitive impairment in longterm users can be detected in up to half of the subjects, compared with 16% of controls, but the issue of reversibility with prolonged abstinence is unresolved. Cognitive toxicity is more common with benzodiazepines than other anticonvulsants, with the possible exception of phenobar-bital (84). 

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