Foundayo Interactions: Medicines to Be Careful Combining It With
Foundayo (orforglipron) has a specific, named list of interacting medicines in its UK patient leaflet: some raise the amount of Foundayo in your blood, some lower it, and a few work the other way round, with Foundayo affecting them instead. Two further interactions work differently - other diabetes medicines, and blood pressure medicines. None of this is complete, so the instruction that matters more than any single named medicine is straightforward: tell your doctor or pharmacist about everything you're taking, prescribed or not.
Key takeaways
- Foundayo's UK leaflet names specific medicines that increase or reduce how much Foundayo is in your blood, plus a separate, shorter list of medicines whose own levels Foundayo can raise.
- Some ordinary, commonly prescribed medicines are on this list: a standard antibiotic (clarithromycin) and standard epilepsy medicines (carbamazepine, phenytoin) among them, not just unusual ones.
- St John's Wort, a herbal product, can reduce how well Foundayo works - easy to overlook, but stated directly in the UK leaflet.
- Combining Foundayo with a sulfonylurea, insulin, or blood pressure medicine has a clear, stated next step: your doctor may adjust the dose of the other medicine, not refuse you Foundayo.
- This list isn't exhaustive. Always tell your prescriber or pharmacist about every medicine, supplement and herbal product you take, whether or not it appears here.
Medicines that can increase Foundayo levels in your blood
Foundayo's UK leaflet names five medicines that can increase how much orforglipron ends up in your blood: clarithromycin (a commonly prescribed antibiotic for chest and skin infections), itraconazole and ketoconazole (both used for fungal infections), and ritonavir and telaprevir (both antiviral medicines).
In practical terms, more Foundayo in your blood generally means a stronger effect - and, since the very common side effects (nausea, constipation, diarrhoea, vomiting, indigestion, stomach pain) are dose-related, a higher chance of noticing more of them. It doesn't mean you can't take both medicines together; the UK leaflet flags this as something your doctor or pharmacist needs to know about, not as a combination it rules out.
Medicines that can reduce Foundayo levels
A different six items on the list work the opposite way, lowering the amount of Foundayo in your blood: carbamazepine and phenytoin (both used for epilepsy), rifampicin (an antibiotic, including for tuberculosis), bosentan (used for pulmonary hypertension), efavirenz (an antiviral medicine), and St John's Wort (Hypericum perforatum), a herbal product used for low mood and anxiety.
That last one is easy to miss, because it doesn't feel like "a medicine" in the way a prescription does. If you're taking a St John's Wort supplement alongside Foundayo, it's worth mentioning specifically. Herbal doesn't mean it can't interact.
Reduced Foundayo levels carry a different consequence from the increase list above: instead of a stronger effect, Foundayo may work less well for weight management or blood sugar control while the interacting medicine is on board - worth knowing if you start one of these medicines partway through your titration, since it can be hard to tell whether a dose step isn't working because of the interaction or for another reason.
Medicines whose levels Foundayo can increase
The direction runs the other way for three medicines: Foundayo can increase the amount of simvastatin, rosuvastatin (both used to lower cholesterol) and topotecan (a cancer treatment) in your blood - here, Foundayo is affecting the other medicine, not the other way round. If you take a statin such as simvastatin or rosuvastatin, mention it when you start Foundayo, so your prescriber can decide whether anything needs monitoring.
The table below pulls all three lists together for a quick check:
| Direction | Medicines named in the UK leaflet |
|---|---|
| May increase Foundayo levels | Clarithromycin, itraconazole, ketoconazole, ritonavir, telaprevir |
| May reduce Foundayo levels | Carbamazepine, bosentan, efavirenz, rifampicin, phenytoin, St John's Wort |
| Foundayo may increase this medicine's levels | Simvastatin, rosuvastatin, topotecan |
This table is a quick reference, not a substitute for telling your prescriber about every medicine you take: see "always tell your prescriber" below for why.
Other diabetes medicines: sulfonylureas and insulin
If you're using a sulfonylurea (another diabetes medicine) and/or insulin, taking Foundayo alongside them raises the risk of low blood sugar (hypoglycaemia) - not because Foundayo's own blood level changes, but because two blood-sugar-lowering effects add together. The UK leaflet states directly that your doctor may reduce your dose of insulin or sulfonylurea before you start Foundayo to manage this risk, one of the few interactions here with a stated, concrete next step rather than just a general caution. You'll also usually be asked to test your blood glucose levels as instructed while this is being managed.
Warning signs of low blood sugar include headache, drowsiness, weakness, dizziness, feeling hungry, confusion, irritability, a fast heartbeat and sweating - Foundayo's side effects covers how often this happens with each combination. If symptoms don't settle the way you've been told to expect, treat it as advised and get help promptly - see when to seek urgent medical help while taking Foundayo if you're unsure.
Pharmacist insight: this combination isn't a reason to avoid Foundayo if you're on insulin or a sulfonylurea - it's one of the most actively managed interactions on this page, precisely because it's well understood. What matters is the conversation happening before you start, not after you notice something's changed. -Alessandro Grenci, Superintendent Pharmacist at medino
For the fuller clinical-practice picture of combining Foundayo with other diabetes medicines, including how this played out in trial evidence, see Foundayo for type 2 diabetes: what the evidence shows.
Blood pressure medicines
Using antihypertensive medicines (for high blood pressure) alongside Foundayo can lower your blood pressure further than either medicine alone. As with the diabetes-medicine interaction, the UK leaflet states your doctor may need to change the dose of your blood pressure medicine to manage this - the same "other medicine's dose may be adjusted" pattern, applied to a different combination. This is usually picked up and managed as a routine part of starting Foundayo, rather than something that rules it out.
The contraceptive pill: a specific interaction worth knowing about
Foundayo can reduce how well oral hormonal contraceptives work - a genuine interaction, with a specific practical answer involving a 30-day window that recurs at every dose increase. That detail matters enough to have its own full page: see Foundayo, pregnancy, breastfeeding and contraception for exactly what to do and when. It's noted here for completeness, but a shortened version risks leaving out the part that matters most, so this page points you to the complete one instead.
Getting the UK picture right: why some interaction lists you'll see look different
If you've looked this up before landing here, you may have seen a page mentioning digoxin, cyclosporine or atorvastatin, or a specific maximum dose - such as capping Foundayo at 9 mg a day with a strong interacting medicine, or capping simvastatin at 20 mg a day. Checked directly against the current UK Patient Information Leaflet, none of that appears in the UK-licensed product information.
That's not because the other information is invented - Foundayo's US prescribing label, approved separately by the American FDA, does include those extra medicines and those specific figures. The UK and US versions of the same medicine can be labelled differently by their own regulators, and Foundayo's UK authorisation is recent enough that a lot of what's easy to find online still reflects the US label without saying so. If you're prescribed Foundayo in the UK, the lists on this page, sourced directly to the current UK leaflet, are the ones that apply to you. Your UK prescriber may still use clinical judgement to adjust a dose in a way the leaflet doesn't spell out in numbers - that's normal, not a sign the UK information is incomplete.
Always tell your prescriber about everything you're taking
The lists above name specific medicines because that's what the UK leaflet states, but the leaflet is explicit that this isn't a complete list. Its own instruction is broader: tell your doctor or pharmacist if you're taking, have recently taken, or might take any other medicines, because either Foundayo or the other medicine could become less effective, or you could be more likely to experience side effects.
That includes over-the-counter medicines, vitamins, and herbal or supplement products, not just prescribed ones. St John's Wort, above, is a direct example of why that matters.
Pharmacist insight: if you realise partway through a course of an interacting medicine that you haven't mentioned it, the answer usually isn't to stop either medicine yourself or skip a dose to be safe - both carry their own risks, especially with a seizure medicine or a course of antibiotics you need to finish. Call your pharmacist or GP practice and ask; it's a quick conversation pharmacy teams field regularly. -Alessandro Grenci, Superintendent Pharmacist at medino
For the complete picture of what Foundayo is and how it's licensed, see the Foundayo overview. For the full precaution list beyond specific medicine interactions, see Foundayo warnings and who should not take it.
Frequently asked questions
I'm about to start a short course of antibiotics - does that mean I need to stop Foundayo?
Not necessarily, and it isn't a decision to make alone. Some antibiotics, including clarithromycin and rifampicin, are named on Foundayo's UK interaction list, but a short, time-limited course is different from an ongoing daily medicine, and your prescriber or pharmacist can usually manage it with monitoring rather than stopping anything. Tell whoever is prescribing the antibiotic that you're taking Foundayo before you start it.
Why do some websites say Foundayo can't be combined with digoxin or atorvastatin when this page doesn't mention them?
Because those sources are usually describing Foundayo's US prescribing label, not the UK one. Checked directly against the current UK Patient Information Leaflet, digoxin and atorvastatin aren't named on the UK-licensed interaction list - simvastatin and rosuvastatin are. If you're prescribed Foundayo in the UK, the UK leaflet is the version that applies to you; if you're taking any of these medicines, mention it to your prescriber regardless of which list it appears on.
Does taking a multivitamin or a common painkiller like paracetamol affect Foundayo?
Neither is named as an interaction on Foundayo's UK leaflet. The general instruction still applies, though: mention everything you're taking, including over-the-counter medicines and supplements, at assessment or a routine review - it costs nothing to mention, and gives your pharmacist the complete picture.
I take a sulfonylurea and I'm worried about low blood sugar - how would I know if it was happening?
Watch for the low-blood-sugar warning signs described above - headache, drowsiness and confusion are among the most commonly reported. Your doctor should explain how to treat it when you start, usually with fast-acting sugar and monitoring. Foundayo's side effects covers exactly how often this happens depending on which other diabetes medicines you're using.
