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