"Reason to be cheerful" chirrups the advertisement for sertraline, a heavyweight antidepressant for people who have suffered a major bout of depression, and who may have attempted suicide. Manufactured by Pfizer, it's marketed in the UK as Lustral an

As a selective serotonin reuptake inhibitor (SSRI), setraline can be fatal if taken with a monoamine oxidase inhibitor (MAOI). Early warning signs of a likely drug interaction include confusion, irritability and extreme agitation which leads to delirium and coma, and possibly death. These reactions have also been noticed in people who have recently come off an SSRI and started a MAOI.

You are advised to wait at least 14 days between taking either of the drugs.

Similarly, the drug should be prescribed to people with liver disease only with caution, Pfizer advises. Overall, it's designed for short term use of up to 16 weeks at a daily dosage of 50 mg.

Even without the help of a MAOI, sertraline can pack a punch all on its own. The most common reactions include gastrointestinal complaints, including nausea, diarrhea, tremors, dizziness, insomnia, sleepiness, sweating, dry mouth and male sexual dysfunction.

In premarketing trials, 15 per cent of the 2700 patients the drug was tested on had to come off sertraline because of an adverse reaction. Central nervous system disorders come a close second to the gastrointestinal ones in terms of frequency, and include headaches, dizziness and tremors.

Then, of course, there are the paradoxical effects of drugs in other words, they cause the very symptoms they are supposed to be treating. Setraline can cause abnormal dreams, aggression, amnesia, delusion, depersonalization, hallucinations, and, yes, depression, aggravated depression and suicidal tendencies.

Reason to be cheerful indeed.