Imipramine (Depsonil), Amitriptyline (Sarotena), Trimipramine (Surmontil), Clomipramine (Clofranil), Amoxapine, (Demolox) Doxepin (Spectra).



Tricyclic antidepressants are commonly used in the treatment of mental depression. The exact mechanism of action is not known. Of all tricyclics, imipramine has been most extensively used. These drugs raise the spirits or improve the mood of depressed patient but do not have an effect in a normal person as is the case with stimulants. In fact, in a normal person these may cause drowsiness, fatigue, and uneasiness. The onset of the antidepressant action of these drugs is very slow, and it usually take 2 to 3 weeks, although the side-effect appear much earlier. It is during this period that the patient needs reassurance. These agents are ineffective in controlling violent symptoms which are sometimes associated with mental depression. In such cases the phenothiazines can be used simultaneously to overcome these symptoms. If the patient also has insomnia, amitriptyline, or trimipramine, which cause some sedation may be helpful. Imipramine is also useful in preventing bedwetting by children. For this reason, it is given at bedtime.

Dosage: The tricyclic antidepressants are given orally in small doses initially for a week or so, and then gradually increased. The smaller doses help in minimizing the adverse effects which generally disappear in due course of time, and the larger doses can then be continued without much discomfort. The doses of imipramime, amitriptyline, and trimipramine are nearly the same. These are usually given in a dose of 50 to 100 mg during the first week and then gradually Increased upto 300 mg. The dose can be further increased or decreased, depending upon the response of the patient.

Adverse Effects: Imipramine and the drugs of this group cause dryness of the mouth, constipation (which may be very severe at times), thirst, difficulty in passing urine, visual disturbances, and palpitation. Clinically, these adverse effects can be minimized by

reducing the doses or changing from one drug to another. In rare cases, skin rashes, neutritis, and fits may occur.

Precautions

These drugs should be administered only to an established patient of mental depression. Once the treatment starts, it must be continued for at least a few months.

If the patient gets excited and agitated, a phenothiazine tranquillizer should be given.

These drugs should not be given to a patient receiving monoamine oxidase inhibitors (such as nialamide), as their interaction may cause high fever, depression of respiration, and marked excitement. A gap of at least two weeks should be allowed before switching from one group of drugs to another.

The action of sedatives like phenobarbitone, meprobamate, diazepam, alcohol is enhanced, and may lead to a dangerous depression of the central nervous system.

These drugs block the blood pressure lowering effect of guanethidine and some other drugs used in hypertension or high blood pressure.

Drugs like phenothiazines or thyroid preparation enhance the action of tricyclic antidepressants; their doses must, therefore, be regulated.

Pregnant and lactating mothers should avoid these drugs as they may cause interference with the development of the foetus.