Drug interactions
Melatonin + Phentermine
Severity: Minor
Melatonin and Phentermine: minor interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Melatonin is sedating while phentermine is a sympathomimetic stimulant that commonly causes insomnia. They have opposing effects on alertness, and phentermine may reduce the sleep benefit of melatonin; no significant harm is expected.
What this interaction means in plain words
Melatonin and Phentermine have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Melatonin belongs to Gastrointestinal Tract; Phentermine belongs to Central Nervous System.
Why it happens
Opposing pharmacodynamic effects on arousal; no established pharmacokinetic mechanism.
What to do
No routine adjustment is needed. Give phentermine early in the day to limit insomnia and reassess if sleep remains disturbed.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Melatonin
- Fluvoxamine + Melatonin Major
- Alfentanil + Melatonin Moderate
- Belladonna and opium + Melatonin Moderate
- Buprenorphine buccal + Melatonin Moderate
- Butabarbital + Melatonin Moderate
- Butalbital + Melatonin Moderate
Other interactions of Phentermine
- Isocarboxazid + Phentermine Contraindicated
- Linezolid + Phentermine Contraindicated
- Phenelzine + Phentermine Contraindicated
- Phentermine + Procarbazine Contraindicated
- Phentermine + Rasagiline Contraindicated
- Phentermine + Selegiline Contraindicated
Frequently asked questions
Can I take Melatonin with Phentermine?
MediHelp rates the interaction as minor. Melatonin and Phentermine have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Melatonin is sedating while phentermine is a sympathomimetic stimulant that commonly causes insomnia. They have opposing effects on alertness, and phentermine may reduce the sleep benefit of melatonin; no significant harm is expected.
How serious is the interaction between Melatonin and Phentermine?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: No routine adjustment is needed. Give phentermine early in the day to limit insomnia and reassess if sleep remains disturbed.
What other medicines interact with Melatonin?
MediHelp also lists interactions of Melatonin with, for example, Fluvoxamine, Alfentanil, Belladonna and opium. The full list is on the Melatonin page.
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