Olanzapine belongs to a class of medications known as atypical (second-generation) antipsychotics. It is used to treat and prevent return of symptoms in Schizophrenia and other mental health related conditions such as:

• Hearing, seeing or sensing things that are not real
• Having mistaken beliefs
• Uncontrolled anger
• Being overly suspicious

It can be used to treat symptoms in bipolar disorder such as:

• Very high mood
• Irritability
• Increased activity and energy
• Depression/low mood

Olanzapine may be used for other conditions. Check with your healthcare professional if you are unsure why you are given this medication.

• Take your medication according to the instructions stated on the medication label.
• Olanzapine should be taken with or without food.
• Olanzapine is available as orodispersible tablets. This means that these tablets dissolve when you put them in your mouth and can be swallowed without water.
• To remove the orodispersible tablets from the blister strip:

1. Dry your hands. The tablets will dissolve if your hands are wet.
2. Follow the dotted lines on the strip and cut out a square containing a tablet.
3. Carefully peel off the foil, starting from the corner.
4. Place the tablet on your tongue. You may take it with or without water. Take the tablet as soon as possible once the foil has been peeled open.

• Olanzapine needs to be taken regularly for a few weeks before you can feel its full benefits. You should not stop taking this medication even if you do not feel better at the beginning. Continue to take this medication even after you feel better to prevent your symptoms from returning.
• Do check with your doctor on how long you will have to be on this medication

• If you forget to take a dose, take it as soon as you remember. However, if more than half of the time to the next dose has passed, skip the missed dose and take the next dose at your usual timing.
• For example, for a medication to be taken two times daily at 8am and 8pm, and you missed your first dose at 8am, skip the first dose if it is after 2pm, and take your second dose at the usual timing at 8pm. Do not take two doses to make up for the missed dose.

Inform your healthcare professional if:

• You are allergic to this medication or any of the other ingredients of this medication
• You are pregnant, planning to become pregnant, or breastfeeding. If you are pregnant and/or breastfeeding, your doctor would have discussed the potential benefits and side effects with you and should you have further questions or concerns, do consult your doctor.
• You are taking any other medications (including those that can be bought without a prescription), supplements, traditional Chinese medicine and herbal products. Some of them may affect how this medication works or cause serious drug interactions.
• You have diabetes. Olanzapine may sometimes worsen blood sugar control in diabetes. Maintain regular check-ups with your doctor.
• You are smoking or have any changes to your smoking habits. Smoking may decrease the amount of Olanzapine that stays in your body.
• You have or have ever had:
  • Other drug allergies
  • Medical conditions such as:
    • Irregular heartbeat or other heart problems, kidney or liver disease, stroke, glaucoma, enlarged prostate (in males)
    • Parkinson’s disease, dementia, seizures (fits), urinary, stomach or intestinal problems, blood disorders, high or low blood pressure, high cholesterol/fats in the blood, history of blood clots, sleep apnoea
    • Phenylketonuria (a condition where there is an increased level of a substance called phenylalanine in your blood) if you are prescribed with Olanzapine orodispersible tablets

The mentioned side effects generally affect up to 10% of patients.

• Constipation 
  • Drink more water (if you do not have any fluid restriction), eat more high-fibre foods, and exercise regularly
  • Speak to your doctor or pharmacist if you need medication to help with your constipation
• Dizziness
  • Get up slowly from a sitting or lying down position
• Drowsiness or feeling tired
  • Avoid driving or taking part in activities that require concentration
  • Discuss with your doctor if you can take your medication at a different time of the day
• Dry mouth
  • Chew sugar-free gum, suck on sugar-free hard candies or ice chips, sip water regularly
• Increase in appetite, weight gain
  • Exercise regularly and eat a healthy and balanced diet
• Increased prolactin hormone in the body (hyperprolactinemia):
  • This may result in changes in menstrual cycle in females (irregular or stopping of menstrual periods) and/or abnormal breast swelling, soreness or secretion (in both men and women)
  • This condition can be managed by speaking to your doctor
• Muscle movement side effects (extrapyramidal side effects) – do speak to your doctor for further management. Examples include:
  • Muscle stiffness and spasms (such as in the face, neck and back), difficulty in speaking or swallowing, twitching, or upward rolling of eyes (symptoms of dystonia)
  • Restlessness or need to keep moving constantly (akathisia)
  • Uncontrollable shaking of limbs (tremors)
• Feeling weak

Most of the side effects listed here will improve with time. Speak with your doctor if any of them continues, worsens or affects your daily life.

The symptoms of a drug allergy include one or more of the following: 

• Swollen face/eyes/lips/tongue
• Difficulty in breathing
• Itchy skin rashes over your whole body

Rarely this medication may cause:

• Confusion, high fever, severe muscle stiffness, irregular blood pressure (signs and symptoms of neuroleptic malignant syndrome)
• Uncontrollable movements such as in the face, tongue, jaw or other parts of the body (tardive dyskinesia)
• Seizures (fits)
• Difficulty controlling or passing urine (urinary retention or incontinence)
• Fast or irregular heartbeat, fainting episodes (signs and symptoms of an abnormal heart beating rhythm (prolonged QTc interval))
• Fever, chills, sore throat and/or mouth ulcers that do not go away (symptoms of blood dyscrasias)
• Severe chest pain, difficulty breathing, or severe pain or swelling in either of the legs (symptoms of venous thromboembolism)
• Excessive hunger, unusual increase in thirst or passing large amount of urine (symptoms of high blood sugar)
• Sudden weakness or numbness in the face, arms or legs, and speech or vision problems (signs and symptoms of stroke)
• Loss of appetite, severe nausea or vomiting, pain in the upper part of the stomach, yellowing of the skin or ‘whites’ of the eyes, dark-brown coloured urine and/or pale/clay-coloured stools (signs and symptoms of a liver problem)

If you experience any of these symptoms, you should stop your medication and see your healthcare professional immediately.

Avoid drinking alcohol while taking Olanzapine as it can cause excessive sleepiness. 

Store in a cool and dry place, away from direct sunlight. Keep this medication away from children. 

Pack this medication into a trash bag and seal it tightly before throwing into the rubbish chute or bin.

Please take note that the above is not a complete list of all possible side effects. If you have any concerns about your medication or if you have other side effects that you think are caused by this medication, please consult your doctor or pharmacist.

If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.

This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (National Healthcare Group, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.

Last updated on Aug 2023