Tricyclic antidepressants

Tricyclic antidepressants (tricyclics), named for their chemical structure (3 rings), came into widespread use in the 1950s.

Some of the available tricyclics include:

  • imipramine (e.g. Tofranil, Tolerade);
  • nortriptyline (e.g. Allegron);
  • amitriptyline (e.g. Endep);
  • dothiepin (e.g. Dothep);
  • clomipramine (e.g. Anafranil);
  • trimipramine (e.g. Surmontil); and
  • doxepin (e.g. Sinequan).

There may be some evidence that tricyclic antidepressants are most effective for people with severe depression compared with those with mild to moderate depression, but they are also given as alternatives to SSRIs (selective serotonin reuptake inhibitors) and are sometimes used in panic disorder, obsessive compulsive disorder and the treatment of chronic pain.

They can produce sedation, so they are sometimes taken at bedtime to help with sleep and to minimise drowsiness during the day.

How they work

These medicines allow more of the brain chemicals serotonin and noradrenaline to be available to nerve cells. This helps nerve signalling in the brain, which can help relieve depression.

Unfortunately, as well as making more serotonin and noradrenaline available, tricyclic antidepressants also affect the amounts of other chemicals, such as histamine and acetylcholine, which are involved in other nerve signalling systems that are responsible for a wide range of other bodily processes. Because of this, tricyclics have a variety of side effects, some of which can be inconvenient.

Side effects

Depending on the medicine your doctor prescribes, you may get some side effects. These can include:

  • drowsiness;
  • difficulty urinating;
  • dizziness when standing up;
  • dry mouth;
  • blurred vision;
  • constipation;
  • changes in sexual function; and, sometimes,
  • weight gain.

However, if you are getting these side effects from one medicine you may not get them from another, as each tricyclic is different.

You may not experience any side effects at all. If you do get side effects, they may go away after a week or so of treatment or continue throughout the course of treatment.

Some side effects can be mistaken for some of the symptoms of depression, so it is very important to talk to your doctor about any side effects you experience — your doctor may need to change the dose or change the medicine altogether.

It’s important that you don’t stop taking tricyclic antidepressants abruptly as this can cause withdrawal symptoms. Talk to your doctor, and if your medicine needs to be stopped, they the dose should generally be reduced slowly.

Alcohol and driving

If you are prescribed a tricyclic, you should avoid alcohol. Alcohol can increase the sedative effects of the medicine and you should not drink and drive while taking tricyclics.

Your doctor may advise you not to drive until they can judge whether you are suffering from any sedating side effects.

Who should not take tricyclic antidepressants?

Tricyclic antidepressants can be dangerous or cause problems if taken by people with:

  • heart problems;
  • prostate enlargement;
  • glaucoma;
  • thyroid problems;
  • diabetes;
  • epilepsy; or
  • a history of head injury.

They can also interact with other medicines, including:

  • other antidepressants;
  • the contraceptive pill;
  • some medicines for high blood pressure; and
  • certain medicines for sleep disturbances.

Your doctor will need to monitor you regularly if you have any of these medical conditions or are taking any medicine that could interact with a tricyclic antidepressant. Even some complementary medicines, such as St John’s wort, may interact with antidepressants, so always tell your doctor if you are taking any.

Mianserin

Mianserin (e.g. Tolvon) is a tetracyclic (4 rings) antidepressant with similar effectiveness to the tricyclics but it appears to have fewer side effects. However, it is more sedating than most tricyclics.

Last Reviewed: 19 December 2012
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References

1. Depression: failure to respond to initial pharmacological therapy (revised February 2013). In: eTG complete. Melbourne: Therapeutic Guidelines Limited; 2013 Mar. http://online.tg.org.au/complete/ (accessed Mar 2013).
2. MayoClinic.com. Tricyclic antidepressants (updated 9 Dec 2010). http://www.mayoclinic.com/health/antidepressants/MH00071 (accessed Mar 2013).
3. Chapter 4.3.1. Tricyclic and related antidepressant drugs. British National Formulary. London: BMJ Group; March 2011.
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