Editor,—We were interested to read Kirwanet al’s report of acute angle closure glaucoma (AACG) associated with the antidepressant paroxetine (Seroxat),1 as we have reported a similar case.2 In Kirwan’s report, AACG occurred within 24 hours of the first dose, suggesting an anticholinergic mechanism. Our case became symptomatic some 2 weeks after daily dosage was commenced, leading us to postulate that the effect could have been mediated by serotoninergic pathways. This raises the possibility of other important ocular side effects with drugs of this class.

Paroxetine is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class. SSRIs act by inducing a gradual rise in postsynaptic levels of serotonin (5-hydroxytryptamine, 5-HT) via desensitisation of the feedback systems which control the rate limiting enzyme in 5-HT synthesis.3 The 5-HT receptors involved have not yet been fully elucidated, and their role in ocular physiology is a subject of ongoing research. In animal studies, serotoninergic stimulation may cause mydriasis, and can have an independent effect in raising the intraocular pressure (IOP).4 Receptors for 5-HT have been demonstrated in the human eye.5

It is therefore possible that SSRIs could have an effect on IOP in humans. Consequently, we should look for raised IOP and open angle glaucoma as a side effect of SSRIs. A recent study has shown a significant short term rise in IOP after a single oral dose of the SSRI fluoxetine (Prozac). Twenty depressed patients were given either fluoxetine 20 mg or placebo in a randomised crossover blinded study, and fluoxetine was associated with a mean IOP elevation of over 4 mm Hg, lasting 6–8 hours.6 We have been unable to find any publication regarding the effect on IOP in the longer term, but we have recently become aware of previously unpublished …