Drug interactions
Olanzapine + Phentermine
Severity: Minor
Olanzapine 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
Olanzapine is sedating while phentermine is a stimulant, so the two have opposing effects on alertness and the net result is unpredictable. Phentermine may also counteract the weight-reducing intent of therapy when used to offset olanzapine-related weight gain, and combined use may affect heart rate and blood pressure.
What this interaction means in plain words
Olanzapine 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.
Olanzapine belongs to Central Nervous System; Phentermine belongs to Central Nervous System.
Why it happens
Opposing central nervous system effects (sedative antipsychotic versus sympathomimetic stimulant); no established pharmacokinetic interaction.
What to do
No dose change is required; monitor heart rate, blood pressure and mental state when starting the combination. Reassess if agitation or psychotic symptoms worsen.
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 Olanzapine
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 Olanzapine with Phentermine?
MediHelp rates the interaction as minor. Olanzapine 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. Olanzapine is sedating while phentermine is a stimulant, so the two have opposing effects on alertness and the net result is unpredictable. Phentermine may also counteract the weight-reducing intent of therapy when used to offset olanzapine-related weight gain, and combined use may affect heart rate and blood pressure.
How serious is the interaction between Olanzapine 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 dose change is required; monitor heart rate, blood pressure and mental state when starting the combination. Reassess if agitation or psychotic symptoms worsen.
What other medicines interact with Olanzapine?
MediHelp also lists interactions of Olanzapine with, for example, Amisulpride, Amoxapine, Apomorphine. The full list is on the Olanzapine page.
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