HeadMeds gives young people in the United Kingdom general information about medication. HeadMeds does not give you medical advice. Please talk to your Doctor or anyone else who is supporting you about your own situation because everyone is different. Please read more important details about our site.

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Return to Clozapine overview
  1. Use and Action
  2. Warnings and side effects
  3. Sex, drink, weight and everything else

You can drink alcohol while taking clozapine, but it could make you very sleepy

  • If you drink alcohol, you can continue to drink alcohol while taking clozapine but having the two together might make you very sleepy.
  • You could feel unsteady and fall.
  • So, during the first few days, it might be best to stop drinking alcohol until you see how the medicine affects you.
  • If you want to drink alcohol, remember that you might be sleepy and make sure you can get home safely.
  • Too much alcohol (getting drunk) whilst taking clozapine can be very dangerous and affect your breathing.

Do not drive a car or ride a bike just after you start taking clozapine

  • Clozapine may make you feel tired or dizzy, and may make your eyesight blurred, when you start taking it.
  • This could affect you if you drive a car, ride a bike, or do anything else that needs a lot of focus. It might be best to stop doing these things for the first few weeks, until you know how it affects you.
  • Do not worry - most people do these things as normal while taking clozaril.

Clozapine is not a banned substance in sport

  • Clozapine is not a banned substance in sport.
  • If you get a side-effect like tiredness, dizziness or blurred eyesight, however, this might cause a problem for sports where you need a lot of focus.
  • Do not worry - most people do all these things as normal while taking clozapine.

Your weight can be affected by clozapine

  • A side-effect of clozapine can be weight loss or weight gain, but weight gain is more common.
  • It is hard to know how it will affect each person who takes it.
  • Talk to your doctor about this if it worries you.

Clozapine does not mix well with drugs 

  • Antipsychotics block the effect of dopamine, so this means the ‘high’ may not be as ‘high’ as before from any drug.
  • You may be tempted to increase your dose of the drug to make up for it, but this could be dangerous.
  • Cannabis can make drowsiness worse with clozapine.
  • Cannabis can reduce the level of clozapine in your body.
  • Methadone can make drowsiness worse with clozapine.
  • Clozapine could increase the level of cocaine in your body, but could reduce the level of happiness that you feel when taking cocaine.
  • Clozapine and stimulant drugs such as Amphetamines can affect the heart and this can be dangerous when taken together.

Let your family and friends know you are taking clozapine so they can support you and help you look out for side effects

  • The side-effects of clozapine might put a strain on your friendships and relationships, especially in the first few days of taking it.
  • You could feel restless or agitated, confused or even delirious.
  • These side-effects should get better after a few days.
  • You should then be getting the good effects of clozapine, and that should improve your relationships in itself.
  • It might actually be a great idea to choose a good friend to tell about your medicine when you start taking it. (Or - even better - to take one with you to the doctor before you start taking it!)
  • They could look at the medicine leaflet, or at this website.
  • They could help you to understand whether the medicine changes your behaviour, or gives you side-effects (sometimes it is hard for us to see it ourselves).

Clozapine can have side-effects that might affect your sex life

The good effects of clozapine may have a good effect on your sex life as your symptoms settle and you can concentrate on your relationships.

There are some side-effects that include:

  • For men, having a painful erection that lasts for a long time (priapism)
  • If you get a skin reaction, or a weight change, you just might not feel as sexy.

These effects should pass after the first couple of weeks. If they do not, and this is a problem for you, go back to the doctor and see what else you could try.

We do not know if clozapine can affect fertility

We have no information about studies of clozapine on human fertility.

Use good contraception while you are taking clozapine

  • If you have been taking other antipsychotic medicines before lithium, your periods may have been affected.
  • Women taking clozapine go back to a normal period pattern.
  • We do not know if clozapine can affect the development of a baby in the womb.
  • Women taking clozapine should use good contraception so that they do not become pregnant.
  • If you want to get pregnant, talk to your doctor about taking clozapine.

Clozapine can cause side-effects in newborn babies

Clozapine is passed to babies in breast milk, so talk to your midwife about feeding options

  • If you take clozapine in the last 3 months of your pregnancy, the baby may get some symptoms when it is born.
  • These could be shaking, muscle stiffness and/or weakness, sleepiness, agitation, breathing problems, and difficulty in feeding.
  • Tell your midwife or doctor that you are taking clozapine, and they can help you to look out for these side-effects.
  • Clozapine passes to the baby in breast milk, and could cause side-effects
  • Bottle feeding may be better for the baby if you take clozapine.

If you start or stop smoking while you are taking clozapine, you may have to change your dose

  • Cigarette smoke affects the amount of clozapine in your body.
  • If you smoke, you will probably need a higher dose of clozapine than someone who does not smoke.
  • Tell your doctor if you smoke, so that you get the right dose for you.
  • If you stop smoking or change to e-cigarettes or nicotine replacement products like patches, the body clozapine level rises and you might need to reduce your dose of clozapine slowly over one week
  • If you (re)start smoking, you will probably need to increase it again
  • Go to your doctor for advice if you stop or start smoking.

Clozapine levels can be changed by high doses of caffeine

  • If you drink a lot of coffee, cola drinks or caffeine drinks, it can increase your level of clozapine in the body and this might be dangerous.
  • If you suddenly stop drinking caffeine, it could make the level fall.
  • Do not make any changes to your diet and drinks before talking to your doctor, so they can watch your clozapine levels.

Some people may wet the bed when taking clozapine

  • Up to 1 in 5 people who take clozapine may start to wet the bed.
  • If this happens to you, do not have drinks just before bedtime.
  • There are medicines available to treat this problem – talk to your doctor if it happens to you before you make a decision to stop your clozapine.

Some people may drool when they take clozapine for the first time

  • People taking clozapine can make more saliva than usual, which might make them drool
  • Some studies suggest that people on clozapine do not make more saliva, but that it is not swallowed as well as usual when the medicine is being taken
  • It usually happens early on in treatment, and gets better over the first few months
  • See your doctor if this happens to you, as they need to know about it, and you can get treatment for it