A Basic Guide to Antidepressants: Types, Dosage, Side Effects and Other Helpful Information

Myths about antidepressant medicines include they will change your personality, deaden your feelings or make you feel numb. If these do occur, see you doctor. It may be from the depression or you may not be on the right medication or the dose may be incorrect.

It is important to discuss with your doctor if you are trying to get off (or switch) your antidepressant medication. Your doctor can help you taper off slowly and minimize any adverse effects. For example, some drugs prescribed for depression are short acting or have a short-half life (i.e. remain in your body for a short time) and as a result people may experience withdrawal symptoms or SSRI discontinuation syndrome (see below) when stopping too quickly.

There has been concern regarding increased suicide risk and worsening of depression with antidepressant use among children. Short-term studies have shown a greater risk of suicidal thinking and behavior among children who use antidepressant medication during the first few months of treatment. Upon starting depression medicine or a change in dosing, children should be carefully monitored for any unusual behavior, increase in depressive symptoms or suicidal thinking and behavior. Similarly, adults with depression and other psychiatric illnesses (and a history of suicidal behavior) should also be closely monitored.

Below are the different types of depression medication, broken down by drug class. The list of anti-depressants includes antidepressant names (brand / manufacturer & generic), typical daily dosage for an adult, potential antidepressant side effects and other common uses³. The information provided pertains to adults and not children.

Types of Anti-depressants

Selective Serotonin Reuptake Inhibitors (SSRIs)

SSRI medications change brain chemistry by increasing the neurotransmitter, Serotonin. This increase is accomplished by blocking the process (which is called reuptake) by which Serotonin is eliminated. They are the most popular class of antidepressant drugs that are prescribed because of their lower adverse effects and safety (higher toxic dose) compared to other types of depression medicine. SSRIs are also considered depression anxiety medications because they treat anxiety among other mental conditions. Overall, these anti-depressant drugs are not prescribed for treating manic depression (which is characterized by episodes of depression and/or extreme elevated mood or irritability).

For some SSRI medication, especially ones (e.g. Paxil, Zoloft, Effexor) that remain in the body for a short time, can cause a set of withdrawal symptoms called SSRI discontinuation syndrome when these anti-depressant medicines are stopped or decreased. When this occurs, you may feel like you have the flu and experience symptoms like fatigue, nausea, chills, diarrhea, headache, vomiting and dizziness. These symptoms will vary in intensity and may last from one to seven weeks.

Tricyclic Anti-depressants (TCAs)

A class of anti depression drug that is named after its chemical structure (a three ring molecular core). In addition to increasing levels of Serotonin, TCAs affect Norepinephrine, Dopamine and to varying degrees Acetylcholine and Histamine. In the past, these depression pills were the first choice in treating depression until SSRIs and new antidepressant medications were developed. These anti-depressants are prescribed less often because they have more unpleasant side effects than SSRI medications and some are potentially dangerous such as a lower toxic/lethal dose and effects on the heart. Tricyclics are often prescribed when someone is experiencing resistant depression or not responding to SSRI meds.

Because its effect on the neurotransmitters Histamine and Acetylcholine, Tricyclic medicines can cause drowsiness and anticholinergic side effects which include dry mouth, rapid heartbeat, blurred vision, constipation and difficulty urinating. TCA medication use in the elderly should be done with caution because of these adverse effects and others such as confusion, delirium and sedation. Overall, this class of anti-depressants have similar side effects, but differ in terms of level of sedation and anticholinergic side effects (see table below).

Example of Potential Side Effects²: dry mouth, sedation or drowsiness, blurred vision, rapid heartbeat, constipation, difficulty urinating, confusion or disorientation, nausea, increased appetite or weight gain, tremor, dizziness when changing positions, hypotension, weakness, change in sexual desire / decrease in sexual ability, irregular heart rhythm, headache

Monoamine Oxidase Inhibitors (MAOIs)

MAOIs were the first medicines developed to successfully treat depression. MAOIs are named after an enzyme (monoamine oxidase) that breaks down neurotransmitters which include Serotonin and Norepinephrine. Since MAOIs inhibit this break down, the levels of these neurotransmitters are increased. These depression medications are used to treat severe or atypical depression which is associated with symptoms such as anxiety, increased sleeping, overeating, weight gain, rejection sensitivity and temporary improvement in mood in response to positive events. These anti-depressants are often prescribed when other depression meds have not been effective.

These medicines are not prescribed as often as SSRIs or TCAs because of serious side effects and interactions with certain foods. For example, foods containing a high level of tyramine cannot be taken with MAOIs (e.g. aged cheeses, sour cream, yogurt, cured meats, dry sausages, wine, beer, soy sauce, banana peel, liver, fava or broad bean pods, anchovies, pickled herring, caviar, yeast extracts and sauerkraut). MAOI anti-depressants and these foods may interact and increase blood pressure to dangerous levels. There are many drug interactions (e.g. over-the-counter cold medicines, nasal sprays) with these antidepressant meds. It is important to inform your doctor about any other medications you are taking while on MAOIs.

Example of Potential Side Effects2: dietary interactions, headache, insomnia or sleep problems, change in blood pressure (blood pressure crisis), drowsiness, nausea, dry mouth, constipation, blood changes/problems, dizziness when changing positions, fluid retention, tremors, change in sexual ability, weakness, stomach upset or pain, blurred vision, restlessness, urinary problems

Other Antidepressant Medicines

These drugs don’t fit in the above categories. These anti-depressants have a combination of different properties and effects on neurotransmitters. Most of these depression medications also affect Serotonin and/or Norepinephrine except Wellbutrin, which affects more Dopamine and Norepinephrine than Serotonin and Eldepryl, which primarily affects Dopamine.

Notes:

1. Some people may take an effective dose that is outside this range. Information for Typical Daily Dosage Range obtained from “Alphabetical Checklist of Dosages and Uses of 100 Common Psychotropic Medications“ by Ed Zuckerman, Ph.D. and Dan Egli, Ph.D.
2. The side effects described give only a sample of the most common and do not comprise a complete listing. Other less common and rarer adverse effects have not been included. Please consult a psychiatrist, physician or health care provider for more information. Side effects information was obtained from the drug’s manufacturer.
3. Other common uses include FDA approved and anecdotal uses (commonly reported but not officially studied). Other common uses do not comprise a complete listing.
4. The manufacturer has withdrawn this anti-depressant. Often the generic version is still available.
5. Source: “A Primer of Drug Action” by Robert M. Julien, M.D. Ph.D.

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The medication and depression information provided is for educational and informational purposes only. This information should not replace the advice of a physician, psychiatrist or health care provider. Before taking any action, please consult with a health care professsional. Please see Terms of Use for more information.