Clozapine monitoring

Can I take other medicines with clozapine?

Clozapine can interact with other medicines, e.g some antibiotics.

You should check with your doctors or pharmacist before you take any other medicines, including herbal medication, vitamin supplements or medication that you have bought over the counter at a pharmacy.

What if I want to stop taking clozapine?

If you feel you want to stop taking clozapine, discuss this with your nurse or doctor first. Your mental health may start to deteriorate and you may get withdrawal symptoms (nausea, diarrhoea, headache, restlessness, sweating) if you stop taking clozapine suddenly.

Regular blood tests

Roughly 3 in every 100 people will get low white blood cells caused by clozapine. To make sure it is safe for you to take, the makers of clozapine are required to run a system to regularly check and monitor patients’ blood.

Your blood will be tested every week initially. After 18 weeks, you should need a blood test only every fortnight. After 12 months, you may only need a blood test every 4 weeks.

Pharmacy will only supply your clozapine if your blood result has been checked. If you miss a blood test, please arrange another blood test as soon as possible and tell your clozapine nurse or pharmacy technician.

If you do not have your regular blood tests, Pharmacy will not be able to give you your clozapine.

How much should I take?

Try to develop a routine for taking your clozapine that is easy for you to stick to.

Do not take more or less clozapine than has been prescribed without talking to your psychiatrist.

If you think you may have taken too much clozapine, contact your nurse or your doctor immediately, or go to your nearest A&E.

Missed doses

If you forget to take a dose, take the dose as soon as you remember. However, if it is nearly time for your next dose, leave out the forgotten tablets and take your next dose at the right time. Do not make up the missed dose by taking more.

If you forget to take your clozapine for more than 48 hours you must contact your clozapine nurse or psychiatrist.

You will not be able to carry on taking the dose you normally do and your clozapine needs to be increased gradually back up to your normal dose. This is so you do not experience any severe side effects.

Side effects

Clozapine, like all medicines, can cause side effects. Some people get more side effects than others. Make sure you understand what the possible side effects are and what to do about them.

Tell your doctor if you are experiencing troublesome side effects.

Tell your doctor immediately if you are experiencing fever, jerking or seizures.

Constipation

Constipation is a very common side effect but can lead to very serious complications. Do not ignore this side effect. Drink plenty of water and eat a healthy diet. Speak to your nurse, doctor or pharmacist if constipation doesn’t improve.

Smoking

If you stop or start smoking or change to e-cigarettes (vape) or NRT (patches, gum, in-halators and nasal sprays etc.) please inform your clozapine nurse or psychiatrist immediately.   Changes in smoking habits can have a big effect on the amount of clozapine in your bloodstream and you may get more side effects. This is to do with the smoke you inhale from tobacco, not the nicotine. For some people, this could be serious.

Measuring the amount of clozapine in your blood

Occasionally your psychiatrist may wish to check the level of clozapine that is in your blood. This is usually done to check you are on the right dose, particularly if you have developed side effects or recently stopped or started smoking cigarettes.

Your nurse will take a blood sample and the results will help your psychiatrist decide whether to change your clozapine dose. For this test you will need to omit your morning dose of clozapine. Your clozapine nurse or CPN will advise you when you need to do this.