Drug interactions
Lorlatinib + Norethisterone
Severity: Major
Lorlatinib and Norethisterone: major 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
Lorlatinib is a moderate CYP3A inducer and can reduce norethisterone concentrations, so contraceptive efficacy may fall. Loss of cycle control and unintended pregnancy are possible.
What this interaction means in plain words
Lorlatinib and Norethisterone can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Lorlatinib belongs to Oncology; Norethisterone belongs to Endocrine.
Why it happens
Induction of CYP3A4 by lorlatinib increases the hepatic and intestinal metabolism of norethisterone.
What to do
Use a nonhormonal contraceptive method (such as copper IUD or condoms) instead of, or in addition to, hormonal contraception during lorlatinib therapy and for several weeks after stopping. Reassess bleeding pattern and adjust the contraceptive plan as needed.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Norethisterone
- Acitretin + Norethisterone Contraindicated
- Amobarbital + Norethisterone Major
- Apalutamide + Norethisterone Major
- Belzutifan + Norethisterone Major
- Bosentan + Norethisterone Major
- Brigatinib + Norethisterone Major
Other interactions of Lorlatinib
- Amobarbital + Lorlatinib Contraindicated
- Apalutamide + Lorlatinib Contraindicated
- Butabarbital + Lorlatinib Contraindicated
- Carbamazepine + Lorlatinib Contraindicated
- Enzalutamide + Lorlatinib Contraindicated
- Fosphenytoin + Lorlatinib Contraindicated
Frequently asked questions
Can I take Lorlatinib with Norethisterone?
MediHelp rates the interaction as major. Lorlatinib and Norethisterone can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Lorlatinib is a moderate CYP3A inducer and can reduce norethisterone concentrations, so contraceptive efficacy may fall. Loss of cycle control and unintended pregnancy are possible.
How serious is the interaction between Lorlatinib and Norethisterone?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Use a nonhormonal contraceptive method (such as copper IUD or condoms) instead of, or in addition to, hormonal contraception during lorlatinib therapy and for several weeks after stopping. Reassess bleeding pattern and adjust the contraceptive plan as needed.
What other medicines interact with Norethisterone?
MediHelp also lists interactions of Norethisterone with, for example, Acitretin, Amobarbital, Apalutamide. The full list is on the Norethisterone page.
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