Fenfluramine/Dexfenfluramine
Brand names [Fenfluramine] Ponderax [Dexfenfluramine] Adifax.
Used in the following combined preparations None
General Information
Fenfluramine and dexfenfluramine are closely related appetite suppressants that are given to treat severe obesity in people who have not managed to lose weight using diet alone. Dexfenfluramine may cause fewer side effects than fenfluramine.
Both drugs work by increasing the activity of serotonin, a neurotransmitter, which creates psychological effects such as a reduced hunger sensation. However, treatment with either of these drugs will only bring about weight loss when used in conjunction with a strict diet. They do not alter the psychological reasons for obesity, and weight may be regained once drug treatment stops.
These drugs are licensed for use for not more than three months.
Information for Users
Your prescription is tailored for you. Do not alter dosage without checking with your doctor.
How taken
Fenfluramine SR-capsules. Dexfenfluramine Capsules.
Frequency and timing of doses
Fenfluramine Once daily, 30 minutes before food. Dexfenfluramine 2 x daily, morning and evening, with meals.
Adult dosage range
Fenfluramine 60mg daily. Dexfenfluramine 30mg daily.
Onset of effect
After 2-3 weeks of treatment.
Duration of action
4-6 hours.
Diet advice
Weight loss occurs only if treatment is accompanied by a strict weight-reducing diet.
Storage
Keep in a closed container in a cool, dry place out of the reach of children.
Missed dose
Take as soon as you remember. If your next dose is due within 12 hours, omit it and take the next scheduled dose as usual.
Stopping the drug
Do not stop either of these drugs without consulting your doctor, who will supervise a gradual reduction in dosage. Stopping abruptly can precipitate depression.
Overdose Action
Seek immediate medical advice in all cases. Take emergency action if breathing difficulties, rapid heart beat, collapse, high body temperature, convulsions, or loss of consciousness occur.
See Drug poisoning emergency guide.
Possible Adverse Effects
Rarely, adverse effects may include nausea, vomiting, headache, nervousness, irritability, bad dreams, insomnia, visual disorders,
hypotension, impotence, and loss of libido. These effects may be reduced by a dosage adjustment.
Interactions
Antipsychotics and antidepressants
Do not take fenfluramine or dexfenfluramine within 3 weeks of stopping these drugs.
Antihypertensive, antidiabetic, and sedative drugs
Fenfluramine and dexfenfluramine may increase the effects of these drugs.
Other appetite suppressants
Do not take fenfluramine or dexfenfluramine within 2 weeks of stopping these drugs.
Quick Reference
Drug group Appetite suppressant
Overdose danger rating High
Dependence rating Low
Prescription needed Yes
Available as generic No
Special Precautions
Be sure to tell your doctor if:
You have suffered from depression or are taking antidepressant drugs.
You have long-term liver or kidney problems.
You have pulmonary hypertension.
You suffer from epilepsy.
You have had problems with alcohol or drugs.
You have suffered from anorexia or a psychiatric illness.
You are taking other medications.
Pregnancy
Not recommended. Discuss with your doctor.
Breast-feeding
Not recommended. Discuss with your doctor.
Infants and children
Not recommended.
Over 60
Fenfluramine Reduced dose may be necessary as drowsiness is more likely to occur. Dexfenfluramine Not recommended.
Driving and hazardous work
Avoid such activities until you have learned how fenfluramine or dexfenfluramine affects you because these drugs can cause drowsiness and confusion.
Alcohol
Avoid. These drugs may increase the effects of alcohol.
Prolonged Use
Fenfluramine and dexfenfluramine are not licensed for use longer than 3 months, after which they may be less effective and the risk of side effects is increased. Rarely, damage to the blood vessels in the lungs may occur after prolonged or repeated courses of treatment with either of these drugs.
