Some medicines and herbal remedies can make the morning after pill less effective or change which emergency-contraception option is recommended. This is particularly important with medicines that increase the activity of liver enzymes, because they can lower the amount of levonorgestrel or ulipristal acetate in the body. If you need emergency contraception in Chingford, tell the pharmacist about every prescription medicine, over-the-counter treatment, herbal remedy and supplement you take — including anything you stopped recently.
Do not take an extra emergency-contraception dose or switch between products on your own because of a possible interaction. The right option depends on the exact medicine, when you took it, when unprotected sex happened, your usual contraception and other clinical factors.
Why medicine interactions matter
The two oral emergency-contraception medicines used in the UK are levonorgestrel and ulipristal acetate. Both are broken down in the body partly through liver enzymes. Some medicines “induce” these enzymes — in simple terms, they make the liver process certain medicines faster. That can reduce exposure to oral emergency contraception and may reduce how well it works.
The effect of an enzyme-inducing medicine does not necessarily disappear as soon as the last tablet is taken. For emergency contraception, medicine use during the previous four weeks can still be relevant. This is why a pharmacist may ask about medicines you no longer take as well as your current treatment.
Which medicines and herbal remedies should you mention?
You should give the pharmacist or clinician the exact names of everything you take. The following are examples of medicines or remedies that can be relevant; the list is not exhaustive, and not every medicine used for the same condition has the same interaction risk.
| Medicine / remedy group | Examples that may matter | Why it matters |
|---|---|---|
| Some epilepsy medicines | carbamazepine, phenytoin, phenobarbital, primidone, oxcarbazepine | Some are strong enzyme inducers and can lower oral emergency-contraception medicine levels. |
| Some tuberculosis medicines | rifampicin, rifabutin | Strong enzyme induction can reduce exposure to levonorgestrel and ulipristal acetate. |
| Some HIV medicines | for example efavirenz or nevirapine; some ritonavir regimens may also matter | The interaction depends on the exact antiretroviral regimen, so the medicine name is essential. |
| Antifungal medicine | griseofulvin | Can induce liver enzymes and reduce oral emergency-contraception effectiveness. |
| Herbal remedy | St John’s wort (Hypericum perforatum) | Can induce liver enzymes; recent use should always be disclosed. |
Other medicines can also be relevant for different reasons. A full medication history is therefore safer than trying to decide from a short online list.
Why recent medicine use can change your options
If you have taken a liver-enzyme-inducing medicine within the last four weeks, current UK product information and sexual-health guidance advise that oral emergency contraception may be less reliable. Ulipristal acetate is generally not recommended in this situation because enzyme induction can markedly reduce its levels.
A copper intrauterine device (copper IUD) may be recommended instead when it is clinically appropriate, because its emergency-contraception effect is not reduced by liver-enzyme-inducing medicines. If a copper IUD is not suitable, acceptable or available, a clinician may consider a different levonorgestrel dose in some circumstances. That decision should be made by a healthcare professional — do not double a dose yourself.
Levonorgestrel and ulipristal acetate are not interchangeable
Levonorgestrel and ulipristal acetate work differently enough that medicine history can influence which is preferred. Levonorgestrel is licensed for use within 72 hours of unprotected sex, while ulipristal acetate is licensed for use within 120 hours. Timing is only one part of the assessment: medicines, recent hormonal contraception, body weight or BMI, cycle timing and other factors can also matter.
Ulipristal acetate should not be taken together with levonorgestrel emergency contraception. If you have already taken one type and think you may need further emergency contraception, ask a pharmacist, sexual-health clinician or doctor rather than taking another product without advice.
For more detail on the time windows, see Mount Pharmacy’s guide on when to take the morning after pill.
What about your regular hormonal contraception?
Your usual contraception is also part of the medicine history. Ulipristal acetate acts at progesterone receptors, so progestogen-containing contraception can interfere with its ability to delay ovulation. Current UK sexual-health guidance therefore uses specific instructions about when to start or restart hormonal contraception after ulipristal acetate and how long to use condoms or avoid sex while protection is being re-established.
The exact advice depends on the contraceptive method you use. Tell the pharmacist if you use the combined pill, progestogen-only pill, patch, ring, implant, injection or a hormonal coil, and follow the instructions you are given after emergency contraception.
Could a copper IUD be used instead?
Yes, when clinically appropriate. The copper IUD is the most effective form of emergency contraception and is not affected by liver-enzyme interactions. It must be fitted by a trained clinician within the appropriate time window, so a pharmacy may need to direct you to a sexual-health or other fitting service.
The copper IUD is not automatically the right choice for everyone, but it is especially important to discuss when medicine interactions may make oral emergency contraception less reliable. You can read Mount Pharmacy’s overview of emergency contraception options for a broader pill-versus-coil comparison.
What should you tell the pharmacist or clinician?
A short, accurate medication history helps the clinician assess your options quickly. Be ready to mention:
- The date and approximate time of unprotected sex or contraceptive failure.
- Any other episodes of unprotected sex during the same cycle.
- All prescription medicines, including medicines you take only occasionally.
- Over-the-counter medicines, herbal remedies and supplements — especially St John’s wort.
- Any enzyme-inducing medicine you stopped within the last four weeks.
- Your usual method of contraception and any missed or late doses.
- Any emergency contraception already taken during this cycle.
- Any important medical conditions or allergies the clinician asks about.
If you do not know the name of a medicine, bring the packet, a photograph of the label, your repeat prescription list or the NHS App medication list if available. Do not delay seeking advice while trying to work it out perfectly — tell the clinician what you know and they can help check the rest.
If you have already taken the morning after pill and then remember an interacting medicine
Contact a pharmacist, GP or sexual-health service as soon as possible. Depending on what you took, when you took it and how long it has been since unprotected sex, another emergency-contraception option may still be available. Do not take an additional tablet without professional advice.
If your next period is significantly late, unusual, or you have symptoms that make you concerned about pregnancy, follow the pregnancy-testing and follow-up advice given by the clinician. Severe or worsening lower abdominal pain, fainting, heavy bleeding or feeling acutely unwell needs prompt medical assessment rather than pharmacy-only advice.
Emergency contraception advice in Chingford
Mount Pharmacy provides confidential emergency-contraception consultations in Chingford. The pharmacist will assess timing, current and recent medicines, your usual contraception and other relevant factors before advising on the most appropriate next step. Supply of a particular medicine is never guaranteed and depends on the assessment.
For local support, visit the Mount Pharmacy emergency contraception service or contact the pharmacy for guidance on how to access an assessment.
Frequently asked questions
Which medicines can affect the morning after pill?
Some enzyme-inducing medicines used for epilepsy, tuberculosis or HIV can reduce levels of oral emergency contraception. Griseofulvin and St John’s wort can also matter. Because not every medicine in these groups has the same effect, tell the pharmacist the exact medicine and any recent use.
Can epilepsy medicines reduce its effectiveness?
Some can. Carbamazepine, phenytoin, phenobarbital, primidone and oxcarbazepine are examples of enzyme-inducing epilepsy medicines that can reduce levels of oral emergency contraception. Other epilepsy medicines behave differently, so do not assume your treatment interacts without checking.
Does St John’s wort affect emergency contraception?
Yes. St John’s wort can increase liver-enzyme activity and reduce levels of oral emergency-contraception medicines. Tell the clinician if you take it now or have taken it within the last four weeks.
What should I tell a pharmacist before taking emergency contraception?
Tell them when unprotected sex or contraceptive failure happened, any other episodes in the cycle, all current and recently stopped medicines, herbal remedies and supplements, your usual contraception, and whether you have already taken emergency contraception.
Can a copper IUD be used instead?
Yes, if it is clinically appropriate and can be fitted within the correct time window. A copper IUD is not affected by liver-enzyme interactions and is the most effective emergency-contraception method, but it requires fitting by a trained clinician.
Medical information disclaimer
This article provides general information and does not replace an individual assessment. Emergency contraception is time-sensitive, and medicine interactions can be complex. A pharmacist, doctor or sexual-health clinician should check your exact medicines and circumstances before advising which option is suitable.
