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Antidepressant drugs

Antidepressant drugs are used to treat the symptoms of depression.

Antidepressant drugs
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Antidepressant drugs help to relieve many symptoms of depression, such as despair, lethargy, poor appetite, insomnia, and thoughts of suicide. Some types of antidepressants, such as selective serotonin reuptake inhibitors (SSRIs), are also effective in treating certain other psychological problems, such as anxiety and post-traumatic stress.

People who are depressed have been shown to have reduced levels of certain chemicals called neurotransmitters in the brain. Serotonin and norepinephrine (noradrenaline) are two neurotransmitters that are thought to increase brain activity and improve mood. They are usually reabsorbed by brain cells and inactivated by an enzyme called monoamine oxidase. In a depressed person, levels of serotonin or norepinephrine are frequently lower than normal. Antidepressants work by helping to restore these chemicals to normal levels.

Antidepressants are taken orally and usually take 1-3 weeks to have an effect on depression. Side effects may develop immediately but gradually lessen. Your doctor will usually advise you to take an antidepressant for at least 4-6 months after your depression has lifted to prevent symptoms recurring and then to reduce the dose gradually. You should avoid alcohol while you are taking these drugs because it enhances the sedative effect.

Lithium, which is a mood-stabilizing drug, may be used on its own or in combination with an antidepressant to treat severe depression.

Common drugs

Selective serotonin reuptake inhibitors: Citalopram, Fluoxetine, Fluvoxamine, Paroxetine, Sertraline Tricyclics: Amitriptyline, Clomipramine, Imipramine
Monoamine oxidase inhibitors: Phenelzine, Tranylcypromine Other antidepressant drugs: Maprotiline, Trazodone, Venlafaxine

What are the types of antidepressant drugs?

Most of the drugs used to treat depression belong to one of three main groups: selective serotonin reuptake inhibitors (SSRIs), tricyclics, and monoamine oxidase inhibitors (MAOIs). There are also several other types of antidepressant. All of these drugs treat depression by increasing levels of the neurotransmitters in the brain that lift mood.

SSRIs drugs

These drugs are the most commonly used type of antidepressant. They may also be used to treat anxiety disorders and post-traumatic stress disorder. SSRIs cause fewer side effects than other types of antidepressant and are less toxic if more than the prescribed amount is taken. The drugs work by blocking the reabsorption of the neurotransmitter serotonin, leaving more of the chemical to stimulate brain cells (see How Ssris work). SSRIs may cause side effects, including diarrhoea, nausea and vomiting, reduced sex drive, and headache. They may also cause restlessness and anxiety.

Tricyclics

Tricyclics are often used to treat depression. They interfere with the reabsorption of serotonin and norepi-nephrine in the brain; as a result, levels of these mood-lifting chemicals increase. They are also sometimes used to treat pain from damaged nerves in conditions such as trigeminal neuralgia.

Tricyclics cause a number of side effects, including a dry mouth, blurred vision, constipation, and difficulty in passing urine. The side effects are usually worse when the drug is first started and become less of a problem as you get used to the drug. Tricyclics are dangerous if you exceed the usual dose. They may cause seizures and heart rhythm irregularities, which can be fatal.

Maois drugs

These drugs are usually only used when other types of antidepressant drug are ineffective. They work by blocking the activity of monoamine oxidase (the enzyme that makes serotonin and norep-inephrine inactive) in brain cells. The side effects may include light-headedness, drowsiness, insomnia, headache, a dry mouth, constipation, and other digestive problems. The drugs interact with other drugs and some foods, including mature cheese, pickled herring, broad bean pods, meat and yeast extract, and fermented soya bean extract. It is therefore important that you follow your doctor's instructions. If you plan to stop taking an MAOI, the dose should be reduced gradually to minimize the risk of dangerous changes in blood pressure.

Other antidepressant drugs

Map-rotiline and trazodone are related to tricyclic antidepressants. Maprotiline is used to treat both depression and anxiety when sedation is required. Trazodone is also used to treat depression when sedation is required. It is less likely to cause heart rhythm problems than other tricyclics.

Venlafaxine blocks the reuptake of serotonin and norepinephrine in the brain. It has fewer side effects than many antidepressants, but consult your doctor if you develop a rash while taking it.

Warning

Antidepressant drugs can cause drowsiness and may affect your ability to drive vehicles or operate machinery.

DRUG ACTION: How SSRIs work

SSRI drugs are often used to treat depression. Depression is associated with low levels of serotonin, a chemical that acts on certain brain cells involved in thoughts and mood. Nerve cells in the brain constantly release and reabsorb the chemical serotonin. SSRIs reduce the rate of reabsorption, resulting in higher levels of serotonin in the brain.

Posted 09.09.2010

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