Working of Antidepressants
Antidepressants are a type of medication that is primarily used in the treatment of depression. Depression is thought to be associated with low levels of certain neurotransmitters, particularly noradrenaline (norepinephrine) and serotonin (5-hydroxytryptamine or 5-HT). Most Antidepressant Drugs are therefore designed either to prolong the effects of the neurotransmitters by blocking their re-uptake into the neuron that released them, or to increase the amount that is accumulated in that neuron and so available for release. Most types of neurotransmitters work at several different sites in the brain, and in other parts of the body as well. This means that drugs that interfere with neurotransmitters in the brain will affect the same neurotransmittersin other parts of the body and brain causing ‘side’ effects, that is, not the intended effect of the drug.
Types of Antidepressants
There are almost thirty different kinds of antidepressants available today and there are four main types:
- MAOIs (Monoamine oxidase inhibitors)
- SSRIs (Selective Serotonin Reuptake Inhibitors)
- SNRIs (Serotonin and Noradrenaline Reuptake Inhibitors)
- NASSAs (Noradrenaline and Specific Serotoninergic Antidepressants)
This type of antidepressant is effective, but is used less often because the side effects are often more extreme.
Common side effects caused by these medicines include dry mouth, blurred vision, constipation, difficulty urinating, worsening of glaucoma, impaired thinking and tiredness. These antidepressants can also affect a person’s blood pressure and heart rate. They are not usually recommended for older patients, people who have glaucoma or men who have enlarged prostates.
Monamine Oxidase Inhibitors (MAOIs)
MAOIs are used less commonly than the other antidepressants. They can have serious side effects, including weakness, dizziness, headaches and trembling. Taking an MAOI antidepressant while you’re taking another antidepressant or certain over-the-counter medicines for colds and flu can cause a dangerous reaction. You should not take an MAOI unless you clearly understand what medications and foods to avoid.
Selective Serotonin Reuptake Inhibitors (SRRIs).
Collectively known as Selective Serotonin Reuptake Inhibitors (SRRIs), these were introduced at the beginning of the 1980s. Fluoxetine is probably the best known SSRI (sold under the brand name Prozac).
SSRIs quickly became widely used because they were as effective as TCAs and MAOIs but caused far less troublesome side effects.
Serotonin and Norepinephrine Reuptake Inhibitors (SNRIS)
These medicines are sometimes chosen because they don’t interfere with certain other medicines.
Some common side effects caused by these medicines include nausea (especially in the first two weeks), loss of appetite, anxiety and nervousness, headache, insomnia and tiredness. Dry mouth, constipation, weight loss, sexual problems, increased heart rate and increased cholesterol levels also can occur.
Norepinephrine and Dopamine Reuptake Inhibitors (NDRIs)
This kind of medicine is sometimes recommended for people who also have attention-deficit hyperactivity disorder, cocaine dependence or want to quit smoking.
One should not take this kind of medicine if you have a seizure disorder or bulimia. Some of the common side effects of NDRIs include agitation, nausea, headache, loss of appetite and insomnia. However, this type of antidepressant medication typically has no sexual side effects.
Duration of Antidepressant Medication
People should keep taking the effective dose for at least six months (about 12 months in older people) after the depression has lifted. If you stop treatment too soon, the depression is likely to come back. If you have recurrent depression, you may need to take an effective dose of your antidepressants for several years.
Side Effects of Antidepressants
The most common side effects of tricyclic antidepressants, and ways to deal with them, are as follows:
- Dry mouth – it is helpful to drink sips of water; chew sugarless gum; brush teeth daily.
- Constipation – bran cereals, prunes, fruit, and vegetables should be in the diet.
- Bladder problems – emptying the bladder completely may be difficult, and the urine stream may not be as strong as usual. Older men with enlarged prostate conditions may be at particular risk for this problem. The doctor should be notified if there is any pain.
- Sexual problems – sexual functioning may be impaired; if this is worrisome, it should be discussed with the doctor.
- Blurred vision – this is usually temporary and will not necessitate new glasses. Glaucoma patients should report any change in vision to the doctor.
- Dizziness – rising from the bed or chair slowly is helpful.
- Drowsiness as a daytime problem – this usually passes soon. A person who feels drowsy or sedated should not drive or operate heavy equipment. The more sedating antidepressants are generally taken at bedtime to help sleep and to minimize daytime drowsiness.
- Increased heart rate – pulse rate is often elevated. Older patients should have an electrocardiogram (EKG) before beginning tricyclic treatment.
The newer antidepressants, including SSRIs, have different types of side effects, as follows:
- Sexual problems – fairly common, but reversible, in both men and women. The doctor should be consulted if the problem is persistent or worrisome.
- Headache – this will usually go away after a short time.
- Nausea – may occur after a dose, but it will disappear quickly.
- Nervousness and insomnia (trouble falling asleep or waking often during the night) – these may occur during the first few weeks; dosage reductions or time will usually resolve them.
- Agitation (feeling jittery) – if this happens for the first time after the drug is taken and is more than temporary, the doctor should be notified.
- Any of these side effects may be amplified when an SSRI is combined with other medications that affect serotonin. In the most extreme cases, such a combination of medications (e.g., an SSRI and an MAOI) may result in a potentially serious or even fatal “serotonin syndrome,” characterized by fever, confusion, muscle rigidity, and cardiac, liver, or kidney problems.