Switching to or from Plan B
Switching medications is more nuanced than simply stopping one and starting another. For Plan B (Levonorgestrel), the right protocol depends on whether the switch is within the same class, across classes, the half-life of the medications involved, and any underlying disease control. This page outlines the practical considerations at 1.5mg.
Switching within the same class
Switching from another Hormones and Birth Control agent to Plan B, or vice versa, is usually direct: the prescriber establishes the equivalent dose of Levonorgestrel and the schedule, and the change happens on a defined day. Symptom monitoring during the first weeks confirms the new regimen is delivering equivalent control. Plan B's primary mechanism is delaying or preventing ovulation when taken before the LH surge.
Switching across classes
Switching to Plan B from a different therapeutic class is more involved. Some switches require a washout period (especially when crossing receptor antagonists/agonists or shared metabolic pathways), others use cross-titration where both medications overlap briefly. The prescriber chooses the protocol based on the medications involved, the indication and individual factors at 1.5mg.
Frequently asked questions
Can I switch directly from another medication to Plan B? ▾
Sometimes yes — within the same class, direct switches are common. Across classes, a structured protocol (washout or cross-titration) is usually safer. The prescriber confirms whether direct switch to Plan B at 1.5mg is appropriate.
What should I do if the switch isn't working? ▾
Switching results vary; the underlying condition may need a few weeks to restabilise on the new medication. If symptoms worsen significantly or new side effects appear, contact the prescriber for review rather than waiting indefinitely or self-switching back to the original medication.
More on Plan B
- With alcoholPlan B and alcohol — is it safe to drink?
- With foodShould Plan B be taken with food?
- Side effectsPlan B side effects: common, rare and warning signs
- Dosage guidePlan B dosage guide: how much to take and when
- OnsetHow fast does Plan B start working?
- DurationHow long does Plan B last?
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.