Tricyclic antidepressants
Tricyclics, named for their chemical structure (3 rings), came into widespread use in the 1950s.
Some commonly used tricyclics are imipramine (e.g. Tofranil); nortriptyline (e.g. Allegron); amitriptyline (e.g. Endep); dothiepin (e.g. Prothiaden); 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 migraines and 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 signals in the brain to be normal and so 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, 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 are having — your doctor may need to change the dose or change the medicine altogether.
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 them?
Tricyclic antidepressants can be dangerous if taken by people with heart problems, epilepsy or a history of head injury. They can also interact with other medicines, including the contraceptive pill, and some medicines for high blood pressure and 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: 25 March 2009
- 1. eMIMS Prescribing Information, May 2009
