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Antidepressants - SSRI side effects

Date Created: 14/01/1998   Last Modified: 07/10/2002   Last Checked: 21/10/2002

GI symptoms are more common in patients on SSRIs.

I have had a significant number of patients who have required endoscopy soon after starting a selective serotonin reuptake inhibitor. SSRIs, by the very nature of their action (see other notes), deplete platelet 5-HT. This might be expected to produce a bleeding tendency. Indeed it sometimes does, and there are quite a few reports of this. What is perhaps puzzling is that it does not happen more often; or maybe it does and we do not notice it because we do not look for it.

Serotonin (5-HT) acquired its name in the 1940s. It is a etymological contracture of the descriptive phrase 'serum tonic factor' which it was given because of its ability to cause contractions in preparations of ileum. It is a 'pro-kinetic' neuro-transmitter in the gut.

There is now epidemiological evidence of a significant association between being on SSRIs and having a GI bleed.

This is compounded by co-administration of NSAIDs and aspirin. This adds further weight to the advice about taking careful account of this (small) risk in those with GI symptoms or conditions; this caution may now be extended to those with a history of GI upset, particularly reflux and ulceration.

I have seen a number of cases of transient global amnesia when people have combined quite small quantities of alcohol with SSRIs. I now routinely warn people about this and would ask anyone who thinks they have seen a case to let me know because, to my knowledge, it has not yet been documented in the literature.

There is some concern that the development of a lethargic amotivational state after initial response to treatment may be related to serotonin mediated inhibition of dopamine. This has been adduced to explain the extra-pyramidal side-effects of SSRIs which are documented but not common. This is a little bit worrying especially for older patients who may have impaired dopamine reserves.

Hyponatremia may occur in approx 10 per 1000 patients on some SSRIs and can be a major concern causing significant iatrogenic morbidity. Clinical experience suggests these research figures could be a substantial underestimate; it is prudent to be wary.

Meta-analysis has managed to evince evidence to show that fluvoxamine may actually have more side effects than TCAs as well as being less effective. It also appears worse than the other SSRIs, especially for causing nausea.

Paroxetine may be associated with a higher rate of male sexual dysfunction, sweating and withdrawal symptoms than other SSRIs.

Gillman's maxim No. 2

"The longer a new drug is in use the smaller the side effect advantages are compared with the previously existing drugs."

All text ©Dr Ken Gillman MRC Psych - PsychoTropical Research®


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