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Obsessive-Compulsive Disorder: An Information Guide Centre for Addiction
and Mental Health

Treatments for OCD: Medications

From: Obsessive-compulsive disorder: An information guide ( © 2001 CAMH)

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If left untreated, OCD can be a disabling and chronic illness. In addition to cognitive-behavioural therapy, drug therapy can help to reduce symptoms of OCD.

As outlined in the section, “Regulating of Brain Chemistry”, research as shown that people with OCD often benefit from drugs that increase the levels of serotonin available to transmit messages in the brain.

The main medications that do this are known as serotonin reuptake inhibitors (SRIs). They are the most commonly prescribed drugs in the treatment of OCD, and are also used to treat depression. SRIs belong to a class of drugs called antidepressants.

Most doctors treating OCD with medication will prescribe an SRI. This medication helps to reduce the symptoms of OCD for about 70 per cent of the people who take it. For those who do not benefit from taking SRI drugs, other drug treatments may provide relief. Other drugs may also be prescribed to address specific symptoms, and taken in addition to SRIs. An overview of the range of drug therapy options, with a discussion of side-effects and other concerns, is as follows.

Serotonin Reuptake Inhibitors

There are two types of serotonin reuptake inhibitors (SRIs). The newer kinds are known as "selective" serotonin reuptake inhibitors (SSRIs) because their primary effect is on serotonin neurotransmitters. The SSRIs currently available in Canada are fluoxetine (Prozac), fluvoxamine (Luvox), sertraline (Zoloft), paroxetine (Paxil) and citalopram (Celexa). Of these, citalopram (Celexa) is the newest and its effectiveness has not yet been proven through research. These medications are considered to be equally effective, although some may work for some people and not for others.

Clomipramine (Anafranil) is the oldest and best studied of the SRI medications.
Existing research indicates that clomipramine may be slightly more effective than the SSRIs, with about 80 per cent of people who take it reporting a reduction in symptoms of OCD.

Clomipramine, however is known to have a more complicated set of side-effects than the newer SSRIs. For this reason, most doctors advise people with OCD to try one of the newer SSRIs first. While all SRIs are effective, the newer SSRIs are known to have milder side-effects.

What's Involved in Trying SRIs?

For best results, SRIs should be taken regularly, generally once each day. Most doctors recommend starting at a low dose and then, if the patient tolerates the medication well, slowly increasing the dose. People who take SRIs may experience side-effects, therefore the ideal dose is one that provides the greatest benefit with a minimum of side-effects.

Once a person has begun to take an SRI, he or she should continue for at least three months. This allows time for the dosage to be adjusted correctly and for the benefits of the drug to become clear.When these drugs work, the effects come on gradually. Usually several weeks pass before any change in symptoms is noticed. Then, obsessions and compulsions slowly become less intense. It is important to realize that although these medications can be of great help to some people, only rarely do they provide relief from all symptoms of OCD.

If no benefits are derived from a particular SRI medication after a trial period of three months, doctors often recommend that another SRI be tried. Some individuals respond well to one drug, and not at all to another. If a person does not benefit from the first medication, a second choice may be clomipramine.

It is not uncommon for someone to try two or three SRI drugs before finding the one that works best. People usually try at least three drugs in the SRI class before considering other drugs.

The question of whether or not to take SRIs while pregnant or nursing should be discussed with your doctor. In some cases, the benefit of the drug clearly outweighs the possible risks.

How Long Should I Take an SRI?

When the right SRI drug has been found, doctors usually advise taking the medication for at least six to 12 months. In some cases, it may be best to take the medication for the long term, as there may be a high risk of relapse if the medication is stopped. Even when taken for the long term, these medications are safe and not "addictive."

If people begin to feel better and stop taking their medication too soon, or too quickly, the risk of relapse increases. The decision to stop taking medication should only be made in consultation with a doctor. The following guidelines can help to lower the risk of relapse when a person stops using medication:

  • Lower the dosage gradually by tapering or reducing the medication over a period of time, possibly several months.
  • Follow-up with a health care professional regularly to help monitor the severity of any symptoms of OCD.
  • Combine cognitive-behavioural therapy with medication and use the skills learned to control any symptoms that may arise when medication is discontinued.

Side-Effects of SRIs

People who take SRIs may experience side-effects. For some, the side-effects are mild, an easy trade-off for the benefits of the medication. For others, the side-effects may be more troubling. People often experience the side-effects of SRIs before they experience the benefits.

In general, the side-effects of SRIs diminish over time, allowing people to tolerate these medications quite well over the long term. Some side-effects may be reduced by an adjustment in dose, or by taking the dose at a different time of day.

The side-effects of SRIs have no permanent effect and will disappear completely when the medication is discontinued. When taking SRIs, or any medication, it is important to discuss any side-effects that are troubling you with your doctor.

The possible side-effects of the newer SSRIs are generally considered to be more manageable than the older SRI, clomipramine. Many of the common side-effects of the newer and older drugs are the same. These include dry mouth, sweating, constipation, drowsiness, tremor and sexual side-effects ranging from lowering of sex drive, to delayed orgasm, to inability to have an orgasm. Weight gain is considered to be more of an issue with clomipramine, although it can occur with long-term use of the SSRIs.

Other common possible side-effects of SSRIs are nausea, sleeplessness and headaches.

Other common possible side-effects of clomipramine are dizziness with sudden changes in posture, and blurred vision. Possible, but rare, side-effects are manic episodes and seizures. Individuals with a history of certain heart problems should use clomipramine with caution, as this drug affects how electrical impulses are conducted through the heart.

Drug Interactions with SRIs

When taking SRIs, or any medication, it is always wise to check with a doctor or pharmacist for possible drug interactions before taking any other prescription or over-the-counter drugs.

Generally, the SRIs are safe drugs to use. However, taking the antihistamines terfenadine (Seldane) and astemizole (Hismanal) while taking SRIs can be dangerous. Other types of antihistamines are safe. SRIs are also known to interfere with the effectiveness of some commonly prescribed drugs.

When taking SRIs, it may be wise to avoid alcohol. SRIs may intensify the effect of alcohol, making it more difficult to control how alcohol affects your behaviour. Alcohol may also interfere with the effectiveness of SRIs.

Other Medications

For those who try several SRIs without benefit, there are other medications that may help. In some cases, other types of antidepressants are more effective. In others, a second drug is given in addition to an SRI.

Other Antidepressants

These drugs also affect serotonin, a chemical messenger in the brain, but they work differently from the SRIs.

Older Drugs (Monoamine Oxidase Inhibitors)
The monoamine oxidase inhibitors (MAOIs) are effective antidepressants and are known to have some limited benefits in OCD. The two MAOIs available are phenelzine (Nardil) and tranylcipramine (Parnate). Both are less effective against obsession than are SRIs and both have more complicated side-effects than SRIs. The MAOIs are used to treat OCD only when SRI medications fail.

Newer Drugs
The antidepressants venlafaxine (Effexor), and nefazadone (Serzone) are sometimes prescribed as treatment for OCD. Evidence of their effectiveness, however, is not conclusive.

Secondary Medications

In some cases, a second medication in combination with an SRI can be very helpful in treating the symptoms of OCD. Adding a second drug to a primary drug is known as "augmentation."

Drugs to Relieve Anxiety

These medications have a calming effect and can help reduce anxiety and make it easier to get to sleep. It is not clear, however, if they reduce the intensity of obsessions or compulsions. People trying to improve their symptoms through cognitive-behavioural therapy should avoid benzodiazepine drugs, as they affect short-term memory and learning.

While these drugs can help reduce anxiety, they should be used with caution. When starting one of these drugs, avoid driving or operating machinery until you are used to the effect. Use of alcohol while taking benzodiazepines should be avoided as this combination can be dangerous. Long-term use of benzodiazepines can lead to drug dependence. Withdrawal from these drugs should be monitored by a doctor.

Of these medications, clonazepam (Rivotril) may specifically affect serotonin balance and is a good choice for people with OCD. Other alternatives that are commonly prescribed include lorazepam (Ativan), alprazolam (Xanax), diazepam (Valium), oxazepam (Serax) and temazepam (Restoril).

Buspirone (Buspar) reduces symptoms of anxiety, but it is not yet clear how effectively it reduces obsessions and compulsions. At present, it appears that buspirone may help a minority of people with OCD.


When taken with an SRI, certain antipsychotic drugs, such as haloperidol (Haldol) and pimozide (Orap), may modestly reduce symptoms of OCD. These drugs are especially helpful in relieving symptoms for people who suffer from panic disorder or Tourette's syndrome.

Unfortunately, these drugs are not without risk. People who take antipsychotic medication for many months or years may develop involuntary movements. This condition is called "tardive dyskinesia." For every year that a person receives antipsychotic medication there is a five per cent chance of developing tardive dyskinesia. The effects of tardive dyskinesia cannot always be reversed.

While the newer antipsychotic drugs appear to carry less risk for this severe side effect, there have been case reports of some of these medications making OCD worse. The newer antipsychotic risperidone (Risperidol) has been tested in OCD, with limited benefit.

Mood Stabilizers

Lithium is most commonly prescribed for the treatment of bipolar disorder and is sometimes prescribed in the treatment of OCD. While lithium can be very helpful in relieving symptoms of depression often associated with OCD, it seems to have very little impact on reducing obsessions and compulsions.

The naturally occurring amino acid, L-tryptophan, is found in certain foods. L-tryptophan is essential for the body to produce serotonin.

Based on the evidence that serotonin levels affect OCD, some think that symptoms of OCD may be improved by giving the body what it needs to produce serotonin. Of those who have tried L-tryptophan in combination with an SRI, few have derived any benefit, and any benefit has been very limited.

Although very safe, L-tryptophan can cause sleepiness and is therefore best taken at night.

Herbal Treatments

Certain herbs may have some benefit in reducing symptoms of OCD, but their effectiveness has not yet been tested. For a couple of reasons, people who wish to explore alternative treatments should consult with a knowledgeable doctor:

  • As with all medications, herbal treatments can have unwanted side-effects and may interact with prescription or over-the-counter medications or other botanicals.
  • In North America, the herbal industry is unregulated, meaning that the quality and effectiveness of herbal products is not consistent.

The two types of herbal treatments that may benefit people with OCD are those with, and without, sedating effects.

Herbal Treatments with Sedating Effects

The sedating effects of some herbal medicines are believed to reduce symptoms of anxiety. These plants include German chamomile, hops, kava, lemon balm, passion flower, skullcap, valerian and gota cola. Compounds in these traditional medicines are known to act on systems in the brain in a similar way to the benzodiazepine class of medications.

Research on animals has established the sedating effects of these herbs, but so far there have been no such studies done on humans.

Although these plants appear to be safe, they should be used with caution. They could increase the sedating effects of other medications, including alcohol.

Herbal Treatments without Sedating Effects

Other herbs, such as St. John's wort, Ginkgo biloba, and evening primrose oil have also been suggested for treating OCD and related anxiety disorders. Less is known about how these plants affect anxiety than is known about herbal treatments with sedating effects.

St. John's wort is believed to work in a way similar to the antidepressants, monoamine oxidase inhibitors. Recent research on this herbal treatment has shown that St. John's wort works better than a placebo in treating mild to moderate depression, but more research is needed to confirm these results. The effectiveness of St. John's wort in treating anxiety, and its effectiveness in comparison to SSRIs, has not yet been studied.

The botanical medicines Ginkgo biloba and evening primrose oil have also been advocated for the treatment of anxiety. As with St. John's wort, though, there is little evidence that these medicines are effective.

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