Phentermine

What is this medication for?

Phentermine is used as a short-term aid to help with weight loss in adults who are obese or overweight with weight-related health conditions. It is used together with a reduced-calorie diet, exercise, and behaviour changes as part of a medically supervised weight loss programme.

This medication works by reducing your appetite, which helps you eat less and lose weight.

How should I take or use this medication?

• Do not stop taking your medication without checking with your healthcare professional.
• Take Phentermine once a day, before breakfast or in the early morning.
• Swallow the capsule whole. Do not break, chew or crush the capsule.
• Avoid taking this medication in the evening or at night, as it may cause difficulty sleeping.

What should I do if I forget to take or use this medication?

If you forget to take a dose, take it as soon as you remember if it is not close to the next dose. Otherwise, you should skip the dose and take the next dose at the usual time. Do not take two doses together to make up for the missed dose.

What precautions should I take when taking or using this medication?

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.
• You are taking any other medications, including supplements, traditional medications and herbal remedies.
• You have any other medical conditions, especially:
  • High blood pressure
  • Heart disease
  • Diabetes
  • Thyroid problems
  • Glaucoma (a condition where the pressure in the eye is increased, which can damage the eye's nerve)
  • Epilepsy (a condition that causes repeated fits or seizures)
  • A history of mental health conditions, including depression or anorexia nervosa
  • A history of drug or alcohol abuse
• You are going to receive any vaccination or surgery, including dental surgery.

This medication should not be used in children under 12 years of age or in the elderly.

If you have any questions about this medication, please discuss with your healthcare professional.

What are some common side effects of this medication? ​

These side effects may be temporary. If they are persistent and become bothersome, please discuss with your healthcare professional.

• Fast or irregular heartbeat (palpitations)
  • This medication may cause a fast or irregular heartbeat. Inform your doctor if you experience this.
• Difficulty sleeping (insomnia)
  • Take this medication in the morning to reduce the chance of difficulty sleeping at night.
• Headache
  • Mild pain can be relieved by taking Paracetamol. Inform your doctor if the headache does not get better.
• Dizziness
  • This medication may cause you to feel dizzy or lightheaded. Sit or stand up slowly. Do not drive or operate machinery if you feel dizzy.
• Restlessness, nervousness or irritability
  • Inform your doctor if these symptoms bother you or do not go away.
• Dry mouth
  • Sip water regularly, chew sugar-free gum or suck on sugar-free hard candies to help relieve dry mouth.
• Nausea, vomiting, diarrhoea, constipation or unpleasant taste in the mouth
  • Take small and frequent meals. Avoid oily or spicy food.
  • For constipation, drink enough fluids (at least 2 litres per day) and eat more fruits and vegetables.
• Changes in sexual desire (libido) or impotence
  • These are usually temporary. Inform your doctor if these symptoms bother you.

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

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

You can also find out about drug allergies by watching these videos:

For videos in 中文, Melayu and தமிழ், click here.

Other rare but serious side effects include:

• Signs of high blood pressure, such as severe headache, blurred vision, chest pain or shortness of breath — proceed to the A&E department immediately.
• Signs of a heart attack, which may include chest pain or discomfort, shortness of breath, or pain spreading to the arm or jaw — call 995 for an ambulance and proceed to the A&E department immediately.
• Signs of a stroke, such as sudden severe headache, sudden weakness or numbness on one side of the body, sudden changes to your sight or speech — call 995 for an ambulance and proceed to the A&E department immediately.
• Shortness of breath or difficulty breathing, especially with swelling of the legs — this may be a sign of a serious lung or heart condition. Proceed to the A&E department immediately.
• Mood changes, hallucinations (seeing or hearing things that are not there), or psychotic episodes — inform your doctor immediately or proceed to the A&E department.
  Fits or seizures — proceed to the A&E department immediately.
• Swelling of the face — inform your doctor immediately.

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 or use this medication?

• Monoamine Oxidase Inhibitors (MAOIs): Do not take Phentermine within 14 days of taking MAOIs (a type of medication used for depression). Taking them together may cause a dangerous rise in blood pressure.
• Alcohol: Avoid drinking alcohol while taking this medication, as it may worsen dizziness, lightheadedness and confusion.

How should I store this medication?

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

How do I throw away this medication safely? ​

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