Antidepressant drugs are effective in the treatment of moderate and severe depression, including following childbirth. Antidepressants are not generally recommended for milder forms of acute depression, but may be trialled if the patient is not responding to psychological treatments. There are three major classes of antidepressants: tricyclic and related antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), and monoamine oxidase inhibitors (MAOIs). Choice should be based on the individual patient's requirements, with either a TCA or SSRI generally favoured over an MAOI.

Dosage regimen

* Selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine, are taken once a day.

* Tricyclic antidepressants (TCAs), such as amitriptyline, are taken in divided doses during the day or as a single dose at bedtime.

* The most commonly used monoamine oxidase inhibitor phenelzine is taken three times a day.

Patient's knowledge of the medicine's use

* Explain to the patient that SSRIs and MAOIs can take upto three weeks to work, and that the full effect will not be seen until six to eight weeks have passed.

* TCAs can taken up to two weeks to work.

Is the medicine working?

* Has the patient been taking the correct number of tablets a day for at least four weeks, but without feeling any benefit? If so, refer to the prescriber as the medication strength may need to be increased, or a different agent tried (either in the same or a different class).

Side-effects

* SSRIs commonly cause GI disturbances such as nausea, vomiting and dyspepsia.

* TCAs commonly cause antimuscarinic side effects such as dry mouth, sedation, blurred vision and constipation.

* MAOIs can cause dizziness, drowsiness and a headache.

* If antidepressants are initiated slowly and carefully, tolerance of side effects may develop, but this needs balancing against the need to obtain a rapid therapeutic effect.

Monitoring

* All patients started on antidepressants should be reviewed every one to two weeks initially.

*SSRIs can cause suicidal tendencies. Check whether the patient is harbouring suicideal ideation, and encourage them to seek immediate medical attention if so.

* All antidepressants, but particularly SSRIs, can cause hyponatraemia. The elderly are particularly susceptible, so any such patients reporting drowsiness, confusion or convulsions should be urgently referred.

* Patients who have been taking antidepressants for a long time may want to stop. However, this should only be done under the supervision of the prescriber and only after remission of symptoms has been achieved for a minimum of four months. The antidepressant dose must be reduced slowly, over a period of at least four weeks, to avoid the emergence of withdrawal symptoms.

* Patients with a history of recurrent depression should be advised that they will need maintenance treatment for at least five years, and possibly even indefinitely.

Lifestyle

* Patients on MAOIs should be warned against eating any tyramine-containing foods, such as mature cheese, pickled herrings, and meat or yeast extracts eg. Marmite, because of the risk of a sudden increase in blood pressure. Patients who forget this advice, or who eat meat, fish or poultry that is past its best, and experience a throbbing headache should be referred immediately. The risk persists for up to weeks after an MAOI is discontinued. Similarly, patients on MAOIs should avoid alcohol and low alcohol drinks.

* Exercise can help reduce depression, so encourage the patient to join the gym or try yoga.

* The patient could try computerized cognitive behaviour therapy (CBT). This therapy helps a person to alter negative thoughts into positive ones. The GP will be able to advise on local availability.

Uzma Chaudhry, relief pharmacist, Lloydspharmacy, Oxfordshire

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