About this medication
- Phentermine (Ionamin) is a capsule taken together with a reduced-calorie diet and exercise, for the short-term management of obesity — it is meant for a few weeks of use only, not ongoing long-term treatment.
The reference describes short-term obesity treatment; Canadian product availability must be confirmed.
How to use it
- Take once daily in the morning, before breakfast, or at least 10 to 14 hours before bedtime, to reduce the chance of trouble sleeping.
If you miss a dose
- If you miss a dose, skip it and take your next dose at the usual time the next day. Do not take a double dose, and do not take it late in the day.
Use only under a prescriber’s supervision for the authorised short course; do not increase the dose when tolerance develops.
Pregnancy and breastfeeding
- Do not use this medicine if you are pregnant or breastfeeding.
Avoid pregnancy and breastfeeding.
Before you use it
- Tell your prescriber if you have heart disease, high blood pressure, an overactive thyroid, glaucoma, or a history of drug or alcohol misuse.
- Tell your prescriber about all medicines you take, especially antidepressants (particularly MAO inhibitors) and other stimulant or diet medicines.
- Do not use if you are pregnant, trying to become pregnant, or breastfeeding.
Important warnings
- This medicine is for short-term use only (a few weeks) — do not take it for a longer period than your prescriber has directed.
- Do not combine this with any other weight-loss medicine.
- Get medical help right away for chest pain, a fast or irregular heartbeat, severe headache, or shortness of breath.
Avoid cardiovascular disease, hyperthyroidism, glaucoma, agitation and substance misuse history.
Possible side effects
- Trouble sleeping, dry mouth, feeling restless or irritable, shakiness, and headache.
Insomnia, dry mouth, irritability and tremor.
When to get help
When to get emergency help
- Chest pain, a racing or irregular heartbeat, severe shortness of breath, or fainting.
- Signs of a severe allergic reaction: swelling of the face, lips, tongue, or throat; difficulty breathing; widespread rash or hives.
When to contact a healthcare professional
- If your appetite suppression seems to be wearing off — do not increase the dose yourself.
- If you notice new or worsening anxiety, agitation, or trouble sleeping.
Chest pain, fainting, severe breathlessness or marked palpitations need urgent care.
Other medicines and products
- Do not take with, or within 14 days of, a monoamine oxidase inhibitor (MAOI) antidepressant — this combination can cause a dangerous rise in blood pressure.
- Limit alcohol, which can add to this medicine's stimulant-type side effects.
Avoid MAOIs, other stimulants and unsupervised weight-loss combinations.
Missed doses, storage and accidental exposure
- Store at room temperature, away from light and moisture, locked away from children and anyone for whom it was not prescribed.
Follow your own product’s missed-dose instructions. If you are unsure, ask the Care365 clinical team before taking an extra dose. Contraceptives, injections and modified-release medicines may need a specific plan.
Keep the original packaging and follow its storage, expiry and disposal instructions. Keep medicines away from children and pets. Ask about refrigeration, after-opening limits and safe sharps disposal when relevant.
For suspected overdose or accidental swallowing, contact poison control or urgent medical care promptly. Call emergency services for breathing difficulty, collapse or a seizure.
Key points to remember
- This is a short-term medicine only — plan with your prescriber what happens after you stop it.
- Never share this medicine with anyone else.
These practical points come from the Pharmasist patient handout for the same product monograph cited by this guide.