Nearly one in seven people will be diagnosed with depression at some point in their lives. Antidepressants are medicines used to treat people who have depression.

Most people with depression get better with treatment that includes these medicines. They help increase the number of chemical messengers in the brain (serotonin and norepinephrine) that affect our mood. They are very effective at treating depression. These drugs aren't tranquilisers and generally aren’t addictive.

There are many different kinds of antidepressants, including:

• Tricyclic antidepressants (tricyclics).
• Selective serotonin reuptake inhibitors (SSRIs).
• Monoamine oxidase inhibitors (MAOIs).

Tricyclics:

The tricyclics have been used to treat depression for a long time. They include amitriptyline, desipramine, imipramine and nortriptyline.

SSRIs:

SSRIs are a newer group of antidepressants and include drugs such as fluoxetine paroxetine and sertraline. These medicines tend to have fewer side effects than the tricyclics.

Monoamine Oxidase Inhibitors (MAOIs):

Monoamine oxidase inhibitors (MAOIs) are usually only used when other antidepressants prove ineffective. They may be effective for people with eating disorders (such as anorexia or bulimia) or post-traumatic stress disorder. MAOIs include phenelzine, isocarboxazid, and tranylcypromine.

Mechanism of Action

We do not know how exactly antidepressants work. Antidepressants appear to correct a chemical imbalance or dysfunction in the brains of depressed people. An antidepressant boosts the level of neurotransmitters important in fighting depression.

Each of the major classes of antidepressants - monoamine oxidase inhibitors (MAOIs), tricyclics, and serotonin inhibitors - affects different neurotransmitter systems in a different way.

• Tricyclic antidepressants are a class of traditional drugs that treat depression by boosting the level of several different neurotransmitters (norepinephrine, epinephrine, serotonin, and dopamine)
• MAOIs destroy enzymes responsible for burning up neurotransmitters, boosting the neurotransmitter levels. In general, MAOIs are used to treat those who don't respond to tricyclics.
• Serotonin inhibitors interfere with the re-absorption of one specific neurotransmitter (serotonin).

Selecting an Antidepressant

The complex array of brain chemicals and processes that influence depression tends to differ from one patient to the next; because there's no foolproof way to identify what's causing your depression, prescribing antidepressants may be a trial-and-error process until the right one is found.

The best your GP can do is to look at your symptoms and try to match those symptoms with an antidepressant. If the first choice antidepressant does not work your GP may change you to a different one.
No one antidepressant is more effective than another, and no one drug successfully treats all cases of depression. Only about half of people find relief with the first antidepressant they are prescribed.

Psychotherapy together with antidepressants is slightly more effective than an antidepressant alone. Psychotherapy seems to work by helping you understand your problems and relieving stress that may worsen symptoms.

Your GP generally will consider the following points while choosing an antidepressant:

• If you had depression before and a certain antidepressant worked well, or if any of your blood relatives had depression and a certain antidepressant worked well for them, this might be the best choice of medicine for you.
• The choice of an antidepressant also depends on your health.
• The best medicine for you is the one that gives you the fewest side effects but effectively treats your depression.
• If you have symptoms like sleeplessness, anxiety and lack of energy, your GP will want to choose a medicine that will help you right away with these symptoms.
• If you're taking other medicines, it's important to consider how an antidepressant will work with the other medicines.

MAOI antidepressants may interact  with some foods. Your GP will warn you about this if he is going to prescribe this type of medication

Combining Drugs

If the first drug fails, your GP  may try a different drug. If this second drug also fails, he may try combining several different drugs. It may also involve the use drugs not typically thought of as antidepressants in combination with an antidepressant. They usually include use of lithium, psychostimulants, thyroid hormones, beta-blockers, and anti-anxiety drugs.

Side effects

Different types of antidepressants produce different side effects.
Tricyclics might have the following side effects

• Dry mouth
• Blurred vision
• Increased sleepiness or drowsiness
• Excessive tiredness
• Hand tremors
• Feeling of weakness
• Constipation
• Worsening of glaucoma
• Bladder problems
• Weight gain
• Muscle twitching
• Increased heart rate
• Dizziness when standing up

SSRIs might have the following side effects:

Nausea,particularly in the first few days and usually settles within the first week.

• Vomiting
• Decreased appetite
• Tremor
• Dry mouth
• Sexual dysfunction (inability to ejaculate or to have an orgasm)
• Sleepiness
• Diarrhoea
• Headache
• Insomnia (difficulty sleeping)
• Anxiety

MAOIs interact with certain foods and other medications to produce potentially fatal high blood pressure- your GP or psychiatrist will warn you about which foods to avoid. Other side effects are

• Orthostatic hypotension (a sudden drop in blood pressure upon standing).
• Drowsiness
• Dizziness
• Sexual dysfunction
• Insomnia

If you are getting a lot of side effects, talk to your GP. He may change your dosage or your medicine to get rid of the side effects. Usually, side effects will disappear or diminish in a week or two. In addition, many antidepressants can be taken before bed so the side effects will occur while you sleep.

Talk to your GP about when to take your medicines.

Ask your GP:

When your GP prescribes an antidepressant be sure you understand:

• What to do if you miss one dose or several doses.
• The best time of day to take your medication, and how you should take it.
• Do you have to avoid any particular food during treatment.
• Can you take alcohol while taking antidepressants.
• What side affects you should expect and how you should manage them.
• How long it will take for the drug to work and how you will know when it's working.
• Which side effects are serious enough that you need to contact the GP immediately.
• What drugs might interact with your antidepressant.

Duration of Treatment

When you start your antidepressant, you will not start to feel better for a week or two. You may only gradually start to feel better and for some people it may take up to six weeks for the antidepressant to start working. You may notice that the first thing to improve is your sleep or your appetite comes back, before you feel your mood improving.

Studies have also found that the longer you are on the antidepressant, the less likely you are to relapse after stopping treatment. 70 percent of patients become depressed again if they stop taking their antidepressants too early.

Many GP prescribe antidepressants for six months to a year following the end of a depressive episode, gradually tapering off the dosage over several weeks.

Some people may require indefinite maintenance therapy of  antidepressant. These people include those who have had three or more recurrences of depression, people over 50 who have never had major depression before, those with two episodes and a family history of depression, and people who have had severe, sudden, or life-threatening depressions within the past five years