Side effect

What happens

What to do about it

COMMON (more than about 1 in 10 people might get these)

Sleepiness

Feeling sleepy, drowsy or sluggish for a few hours after a dose

Don't drive or use machinery. Ask your doctor if you can take your clozapine at a different time.

Hypersalivation

You dribble and your mouth gets full of saliva or spit. Your pillow is wet in the morning.

This is not dangerous, but can be upsetting. Your doctor may be able to give you a tablet (e.g. hyoscine) to help this. Propping up pillows at night helps some people a bit.

Hypotension

A low blood pressure - this can make you feel dizzy.

Try not to stand up too quickly. If you feel dizzy, don't drive. This dizziness is not dangerous.

Weight gain

Eating more and putting on weight.

A diet full of vegetables and fibre may help prevent weight gain.
Click here for a few tips on how to help you feel less hungry and lose weight.

Constipation

When you want to poop but can't (the opposite of diarrhoea). You can't pass a motion.

Make sure you eat enough fibre, cereal or fruit. Make sure you are drinking enough fluid. Keep active and get some exercise e.g. walking. If this does not help, ask your doctor or pharmacist for a laxative. If it goes on for more than a few days, contact your doctor as this can be dangerous.

Urinary incontinence, urinary retention, nocturnal enuresis

Not being able to have a wee, or passing urine when you don't want to e.g. during the night.

You should ask your doctor or nurse about this. It may be that a change in dose, or when you take your dose or doses might help. Sometimes taking an anticholinergic (e.g. procycldine) or a low dose of a tricyclic (e.g. amitriptyline) can help.

LESS COMMON (less than about 1 in 10 people might get these)

Extra-pyramidal or Parkinsonian side effects

Having shaky hands and feeling shaky. Your eyes and tongue may move on their own. You feel very restless.

It is not usually dangerous and is a well known side effect. If it is distressing or worries you, tell your doctor. He or she may be able to give you something for it e.g. an anticholinergic drug.

Fever or flu-like symptoms

A high temperature.

Make sure you check with your doctor or pharmacist to make sure you do not have a blood problem. If not, try paracetamol. Always tell your doctor or carer if you get an unexpected fever, sore throat or illness.

Diabetes

You lose weight, pass lots of urine, and feel thirsty and hungry all the time.

Tell your doctor if you get these symptoms. You can then have some simple tests to see if you are getting diabetes. 

Palpitations

A fast heart beat.

Let your doctor know, especially if this happens in the first few weeks.

RARE BUT IMPORTANT (around 1 in 100 people might get these)

Agranulocytosis or neutropenia

Low numbers of white cells in the blood. You may get more infections.

This will be picked up from your blood tests. It happens in about 2 or 3 in 100 people. Always tell your doctor or carer if you get an unexpected fever, sore throat or illness.

Seizures

Having a fit or convulsion.

Stop taking clozapine and contact your doctor immediately.

Cardiomyopathy

Where the heart muscles become inflamed. This leads to chest pain, and an odd heart rate.  

If you get any of these symptoms, you must contact your doctor as soon as possible. You will almost certainly need to stop clozapine. It usually happens in the first 2-3 weeks after starting clozapine.