PsychoTropical Research - Dr Ken Gillman, Serotonin Syndrome, Mirtazapine, Dual Action Drugs. Amnesia - Side effects.

PsychoTropicalResearch, serotonin and serotonin syndrome research.

Amnesia - Side effects

Amnesia - Side effects

Date Created: 04/09/1999   Last Modified: 11/10/1999    Last Checked: 21/10/2002

Memory impairment secondary to drug treatment has probably received insufficient consideration and attention. Anti-muscarinic activity (see 'receptor affinities' and 'delirium') is very undesirable in older people and produces measurable impairment in memory in young subjects also. Benzodiazepines give significant amnesia and the potent short acting ones, when used intra-venously, usually produce complete amnesia for the event (eg gastroscopy).

Mixtures of scopolamine and benzodiazepines have been reported to have been used by criminals to incapacitate crime victims who are subsequently unable to give any account of the events or their assailants.

It is quite possible for such combinations to be given inadvertently; for instance a sea-sickness patch (scopolamine-- anti-muscarinic) and a benzodiazepine for anxiety symptoms related to going in boats. A couple of drinks on the trip and bingo, complete amnesia for the 'Great barrier reef' experience (what's left of it that is).

Mixtures of TCAs (all have at least some anti-muscarinic affinity) and benzodiazepines given for depression may cause significant memory problems. One might also consider 'medical' drugs not usually thought of as having anti-muscarinic properties like cimetidine (see 'Brain failure').

Cimetidine is an especially good example in this context. It inhibits cytochrome P450 3A4 and that will raise blood levels of some potent short acting benzodiazepines like alprazolam (which are metabolised by cytochrome P450 3A4) and potentially exacerbate amnesic effects. That is a good example of a combined pharmacokinetic and pharmacodynamic interaction which requires a high level of knowledge and expertise to predict.