Drug interactions
Ketotifen + Phentermine
Severity: Minor
Ketotifen 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
Ketotifen can cause drowsiness while phentermine is a stimulant, so the two have opposing effects on alertness. There is no established clinically significant interaction, and neither drug reliably cancels the effects of the other.
What this interaction means in plain words
Ketotifen 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.
Ketotifen belongs to Respiratory; Phentermine belongs to Central Nervous System.
Why it happens
Opposing pharmacodynamic effects on alertness; no established pharmacokinetic mechanism.
What to do
No specific action needed. Do not rely on phentermine to offset ketotifen sedation, and advise patients to judge their own alertness before driving.
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 Ketotifen
- Ketotifen + Phenobarbital Moderate
- Ketotifen + Pholcodine Moderate
- Ketotifen + Primidone Moderate
- Ketotifen + Protriptyline Moderate
- Ketotifen + Quazepam Moderate
- Ketotifen + Rotigotine 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 Ketotifen with Phentermine?
MediHelp rates the interaction as minor. Ketotifen 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. Ketotifen can cause drowsiness while phentermine is a stimulant, so the two have opposing effects on alertness. There is no established clinically significant interaction, and neither drug reliably cancels the effects of the other.
How serious is the interaction between Ketotifen 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 specific action needed. Do not rely on phentermine to offset ketotifen sedation, and advise patients to judge their own alertness before driving.
What other medicines interact with Ketotifen?
MediHelp also lists interactions of Ketotifen with, for example, Phenobarbital, Pholcodine, Primidone. The full list is on the Ketotifen page.
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