Types of Antidepressants
There are many different kinds of antidepressants, including:
- Selective serotonin reuptake inhibitors (SSRIs)
- Tricyclic antidepressants (tricyclics)
- Novel antidepressants and others
Like most medicines, antidepressant drugs can cause side effects. Not all people get these side effects. Any side effects you have will depend on the medicine your doctor has chosen for you. Your doctor should talk to you about your medicine.
Selective serotonin reuptake inhibitors (SSRIs)
SSRIs are a group of antidepressants that includes drugs such as escitalopram (brand name: Lexapro) citalopram (brand name: Celexa), fluoxetine (brand name: Prozac), paroxetine (brand name: Paxil) and sertraline (brand name: Zoloft). Selective serotonin reuptake inhibitors act only on the neurotransmitter serotonin, while tricyclic antidepressants and MAO inhibitors act on both serotonin and another neurotransmitter, norepinephrine, and may also interact with other chemicals throughout the body.
Selective serotonin reuptake inhibitors have fewer side effects than tricyclic antidepressants and MAO inhibitors, perhaps because selective serotonin reuptake inhibitors act only on one body chemical, serotonin. Some of the side effects that can be caused by SSRIs include dry mouth, nausea, nervousness, insomnia, headache and sexual problems. People taking fluoxetine might also have a feeling of being unable to sit still. People taking paroxetine might feel tired. People taking sertraline might have runny stools and diarrhea.
The tricyclics have been used to treat depression for a long time. They act on both serotonin and another neurotransmitter, norepinephrine, and may also interact with other chemicals throughout the body. They include amitriptyline (brand name: Elavil), desipramine (brand name: Norpramin), imipramine (brand name: Tofranil) and nortriptyline (brand names: Aventyl, Pamelor). 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.
Other antidepressants exist that have different ways of working than the SSRIs and tricylics. Commonly used ones are venlafaxine, nefazadone, bupropion, mirtazapine and trazodone. Less commonly used are the monoamine oxidase inhibitors (MAOIs).
Some of the most common side effects in people taking venlafaxine (brand name: Effexor) include nausea and loss of appetite, anxiety and nervousness, headache, insomnia and tiredness. Dry mouth, constipation, weight loss, sexual problems, increased blood pressure, increased heart rate and increased cholesterol levels can also occur.
Nefazodone (brand name: Serzone) can give people headaches, blurred vision, dizziness, nausea, constipation, dry mouth and tiredness.
Bupropion (brand name: Wellbutrin) can cause agitation, insomnia, headache and nausea. Mirtazapine (brand name: Remeron) can cause sedation, increased appetite, weight gain, dizziness, dry mouth and constipation. Some of the most common side effects of trazodone (brand name: Desyrel) are sedation, dry mouth and nausea. MAOI antidepressants like phenelzine (brand name: Nardil) and tranylcypromine (brand name: Parnate) commonly cause weakness, dizziness, headaches and tremor.
Interactions of Antidepressants
Antidepressants Can Affect Other Medications You May Be Taking
Antidepressants can have an effect on many other medicines. If you’re going to take an antidepressant, tell your doctor about all the other medicines you take, including over-the-counter medicines and herbal health products (such as St. John’s wort). Ask your doctor and pharmacist if any of your regular medicines can cause problems when combined with an antidepressant. When taken together, some medicines can cause serious problems.
Taking an MAOI antidepressant at the same time as any other antidepressants or certain over-the-counter medicines for colds and flu can cause a dangerous reaction. Your doctor will tell you what foods and alcoholic beverages you should avoid while you are taking an MAOI. You should not take an MAOI unless you clearly understand what medications and foods to avoid. If you are taking a MAOI and your doctor wants you to start taking one of the other antidepressants, he or she will have you stop taking the MAOI for a while before you start the new medicine. This gives the MAOI time to clear out of your body.
Another risk of antidepressants is serotonin syndrome, a drug reaction resulting from the over-stimulation of serotonin receptors. This can occur when an antidepressant is taken either with another antidepressant, with certain recreational and other drugs (see below), or more rarely, even when one antidepressant is taken alone. Symptoms include hyperactivity, mental confusion, agitation, shivering, sweating, fever, lack of coordination, seizure, and diarrhoea.
To minimise the risk of serotonin syndrome, there must be a ‘washout’ period of at least two weeks when switching from one antidepressant drug to another.
Drugs that may induce serotonin syndrome when taken with antidepressants (not a complete list)
- St John’s wort (Hypericum) – herbal antidepressant
- diethylproprion – an amphetamine
- dextromethorphan – found in many cough suppressants
- Buspar (buspirone) – for anxiety
- Selgene, Eldepryl (selegiline) – for Parkinson’s Disease
- anti-epileptics – Tegretol, Carbium, Teril (carbamazepine)
- analgesics – pethidine, Fortral (pentazocine), Tramal (tramadol), fentanyl
- anti-migraine drugs – Naramig (naratriptan), Imigran (sumatriptan), Zomig (zolmitriptan)
- appetite suppressants – phentermine and fenfluramine
- tryptophan – an amino acid
Which Antidepressant Drug Is Best For Me?
Because the neurotransmitters involved in the control of moods are also involved in other processes, such as sleep, eating, and pain, drugs that affect these neurotransmitters can be used for more than just treating depression. Headache, eating disorders, bed-wetting, and other problems are now being treated with antidepressants.
All antidepressant drugs are effective, but certain types work best for certain kinds of depression. For example, people who are depressed and agitated do best when they take an antidepressant drug that also calms them down. People who are depressed and withdrawn may benefit more from an antidepressant drug that has a stimulating effect.
Antidepressants Are Not A Magic Bullet
While antidepressant drugs help people feel better, they cannot solve problems in people’s lives. Some mental health professionals worry that people who could benefit from psychotherapy rely instead on antidepressant drugs for a “quick fix.” Others point out that the drugs work gradually and do not produce instant happiness. The best approach is often a combination of counseling and medicine, but the correct treatment for a specific patient depends on many factors. The decision of how to treat depression or other conditions that may respond to antidepressant drugs should be made carefully and will be different for different people.