8.3 How to Use an Antidepressant

Summary

• Give an adequate dose for an adequate duration
• Avoid premature dosage increase
• Avoid premature change of drugs
• Avoid using antidepressant combinations

 

It has been well established that the major reason for failure to recover from depression is the inadequate or inappropriate use of antidepressant medication or ECT. Full therapeutic doses must be used and if not tolerated, then an alternative medication should be tried. It is important to allow sufficient time for the drug to work and not to give up and change drugs too soon, unless side effects are an issue. Premature increases in doses are not only unnecessary but are expensive and expose the patient to the increased risk of intolerable side effects. For example, when using SSRI's, the starting dose is also the therapeutic dose and at least three to four weeks should elapse before attempting to increase the dose. An adequate course of treatment is generally at least six to nine months.

The practice of combining antidepressants involves considerable risk with little promise of benefit to the patient. There is no good evidence that combining SSRI's with tricyclic antidepressants produces greater efficacy and, because of the potential for undesirable drug-drug interaction this practice is hazardous. The SSRI's to a greater or lesser extent inhibit the liver enzymes (cytochrome P450) which metabolise tricyclics. Combining the two risks exposing the patient to high plasma levels of tricyclic with all the associated risks. Other antidepressant combinations carry significant risk. The combination of other types of antidepressant with MAOI's or clomipramine (Anafranil) may lead to the potentially fatal serotonin syndrome and must be avoided.

8.4 Summary - Rational Use of Antidepressant Drugs

All of the above antidepressants are effective and all have a place in the treatment of depression, although as new drugs are added, the older drugs tend to be used less as first line treatments. The choice of a particular antidepressant should rarely be made on the basis of drug efficacy alone. In general, the newer antidepressants are safer and better tolerated than the TCA's and irreversible MAOI's and overall are a better first choice in mild - moderate depression. But, in order to make a clinically appropriate choice of antidepressant, detailed consideration of the issues above will be needed on a case by case basis.

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