Medication Information Leaflet

What is this medication for?

Varenicline is used, together with education and counselling, to help you quit smoking by reducing the withdrawal symptoms and the satisfying effects of smoking.

How should I take/use this medication?

  • Varenicline may be taken with or without food.
  • Take your medication according to the instructions stated on the medication label.
  • Varenicline needs to be taken regularly for one week or so before you can feel its effect. You should continue to take this medication even if you do not feel the benefits at the beginning.
  • Do check with your doctor on how long you will have to be on this medication. To use the medication to quit smoking, you can either:
    • Set a date to stop smoking and start varenicline one week before the date
    • Start varenicline and quit smoking between days 8 to 35 of treatment
  • Talk to your doctor about the most suitable way to use the medication.
  • Do not stop taking or adjust the dose of this medication without checking with your doctor. You may experience unpleasant effects such as having difficulty in sleeping or feeling more irritable if you suddenly stop taking the medication on your own.
  • You should not be using Varenicline while you are using other medications to quit smoking. Tell your doctor if you are using other treatments to quit smoking.

What should I do if I forget to take/use 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.

What precautions should I take?

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 or have ever had:
    • Other drug allergies
    • Kidney, heart or blood vessels disease
    • Medical conditions such as seizures (fits), depression or other mental health problems

What are some common side-effects of this medication?

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

  • Difficulty sleeping
    • Discuss with your doctor if you can take your medication at a different time of the day
    • Listen to relaxing music at bedtime
    • Avoid eating or drinking too much before bedtime
    • Limit your caffeine intake (such as coffee, tea or energy drinks) at least 8 hours before bedtime
  • Nausea, vomiting or stomach gas
    • Take the medication with or after food
    • Take small but more frequent meals, and avoid fatty or spicy food
  • Drowsiness, dizziness, difficulty concentrating
    • 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
  • 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
  • Increase in appetite, weight gain
    • Monitor your weight, exercise regularly and eat a healthy, balanced diet
  • Headache, strange and/or unusual dreams

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.

What are some rare but serious side-effects that I need to seek medical advice immediately?

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:

  • Shortness of breath, sweating, nausea, sudden dizziness, chest discomfort, or pain that spreads from one or both arms, back, neck, jaw or stomach (symptoms of a coming heart attack, or an acute myocardial infarction)
  • Fast, pounding or irregular heartbeat
  • Seizures (fits)
  • Changes in mood such as feeling depressed, or having thoughts of harming self or others
  • Unusual thoughts, talking, feeling, and acting with excitement that you cannot control (signs and symptoms of mania)
  • Unusual bleeding/bruising
  • Sleepwalking

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

What food or medication should I avoid when I take this medication?

Avoid drinking alcohol while taking Varenicline as it can increase the effects of alcohol and cause excessive sleepiness.

How should I store this medication?

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

How should I throw away this medication safely?

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 Mar 2023

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