Last verified: April 22, 2026 · FDA label reviewed · CYP3A4 table cross-referenced · Pricing verified
Drug Interactions Guide · April 22, 2026
Foundayo Drug Interactions: What to Check Before Your First Dose
Last reviewed:
By The RX Index Editorial Team · Last verified: April 22, 2026
The RX Index is a pricing intelligence and comparison resource for GLP-1 telehealth providers. This article is informational and does not constitute medical advice. Speak with a licensed healthcare provider before starting, changing, or stopping any prescription medication.
If you’re taking Foundayo (orforglipron), or about to start it, the Foundayo drug interactions that actually matter on the FDA label split into four clean tiers: avoid, dose-cap, use backup or monitoring, and no clinically relevant change. The avoid list is much shorter than the internet makes it sound — strong CYP3A4 inducers like carbamazepine, phenytoin, rifampin, and St. John’s Wort, plus ritonavir-containing regimens (Paxlovid). The dose-capped list is exactly two items: clarithromycin (cap Foundayo at 9 mg/day) and simvastatin (cap simvastatin at 20 mg/day). Everything else is either label-cleared, a monitoring situation, or hasn’t been systematically studied.
Here’s the part most pages won’t tell you: Eli Lilly itself states that Foundayo has not been systematically studied with all medications, so an honest page can’t hand you a universal yes/no list. What we can do — and what we did for this page — is cross-reference the FDA-approved Foundayo prescribing information against the FDA’s public list of CYP3A4 inhibitors and inducers, then translate the result into plain-English actions per drug.
What we actually verified
- Foundayo US Prescribing Information — Eli Lilly, revised April 2026 (DailyMed Set ID
8ac446c5-feba-474f-a103-23facb9b5c62). Tables 2–5, sections 2.2, 5.5, 5.9, 7.1, 7.2, 7.3, 8.3. - FDA’s official table of CYP enzyme and transporter interactions — fda.gov, content current as of January 20, 2026.
- Eli Lilly Medical — orforglipron interaction Q&A for healthcare professionals.
- Foundayo FDA-approved Medication Guide (patient-facing, same DailyMed Set ID).
Verification cadence: Re-checked against the FDA label and Lilly’s medical portal quarterly, or within 7 days of any label revision. Provider pricing is re-checked monthly.
The Foundayo drug interactions map at a glance
Short answer: Four tiers. Tier 1 means don’t combine. Tier 2 means take both, but one drug has a dose ceiling. Tier 3 means use it with backup contraception, dose adjustment, or monitoring. Tier 4 is medications the label directly tested with no clinically relevant change, plus drugs not specifically named in the interactions table.
Every row in the tables below comes from one of two places: the Foundayo FDA label’s interaction tables and clinical pharmacology section (label-tested or PBPK-simulated, as noted per row), or a precautionary classification based on the FDA’s public CYP3A4 database (label-precaution). A third confidence category — not specifically named in the label — covers medications where we’re inferring from drug class but don’t have a direct Foundayo study to cite.
Tier 1 — Do not combine with Foundayo
These are the ones the label tells you to avoid. The reasons are either (a) the medication cuts Foundayo’s effectiveness dramatically, (b) the combination produces unpredictably high Foundayo exposure because of dual pathway blocks, or (c) the label specifically states the combination is not recommended.
| Medication or category | Evidence | Why |
|---|---|---|
| Carbamazepine (Tegretol, Carbatrol) | Label-tested | Foundayo AUC ↓ 82%, Cmax ↓ 55% in Lilly’s clinical study |
| Phenytoin (Dilantin) | Label-precaution | Strong CYP3A4 induction expected to reduce Foundayo exposure substantially |
| Rifampin (Rifadin) | Label-precaution | Strong CYP3A4 inducer; Foundayo label advises avoidance |
| St. John’s Wort | Label-precaution | FDA classifies as strong CYP3A4 inducer |
| Enzalutamide, Apalutamide, Mitotane, Ivosidenib, Lumacaftor/ivacaftor | Label-precaution | All FDA-classified strong CYP3A4 inducers |
| Ritonavir-containing regimens (Paxlovid, Kaletra, most boosted HIV regimens) | Label-named | Ritonavir inhibits both CYP3A4 and OATP1B — dual block causes significantly higher Foundayo exposure |
| Another GLP-1 medication (Ozempic, Wegovy, Zepbound, Mounjaro, Saxenda, Rybelsus, Trulicity, Victoza) | Label-named | Foundayo’s label states: “Concomitant use with another GLP-1 receptor agonist is not recommended” |
Tier 2 — Dose-capped combinations
Both drugs can be taken, but one has a hard dose ceiling on the FDA label.
| Medication or category | Cap | Evidence |
|---|---|---|
| Clarithromycin (Biaxin) | Foundayo max 9 mg/day | Label-tested — clarithromycin increased Foundayo AUC 3.5-fold and Cmax 1.9-fold |
| Itraconazole, Ketoconazole (oral), Posaconazole, Voriconazole | Foundayo max 9 mg/day | Label-precaution (strong CYP3A4 inhibitors) |
| Adagrasib, Ceritinib, Cobicistat, Idelalisib, Nefazodone, Nelfinavir, Telithromycin, Tucatinib | Foundayo max 9 mg/day | Label-precaution (strong CYP3A4 inhibitors) |
| Simvastatin | Simvastatin max 20 mg/day | Label-tested — Foundayo doubled simvastatin acid; 2-hour staggered dosing did not eliminate the interaction |
Tier 3 — Backup, monitoring, or dose adjustment
You can take both drugs, but something else changes — a temporary contraceptive backup, a diabetes medication dose reduction, or your prescriber monitors Foundayo effectiveness and may escalate the dose.
| Medication or category | What to do | Evidence |
|---|---|---|
| Oral hormonal contraceptives (combined pills, progestin-only pills) | Use a non-oral method (IUD, ring, patch, implant, injection) or add a barrier method for 30 days after starting Foundayo and 30 days after each dose increase | Label-precaution — Lilly did not study this combination in a clinical trial; flagged based on Foundayo’s gastric emptying effect |
| Insulin (any type) | Prescriber may reduce insulin dose; monitor blood glucose closely | Label-named hypoglycemia risk |
| Sulfonylureas (glipizide, glimepiride, glyburide) | Prescriber may reduce sulfonylurea dose | Label-tested — 7% hypoglycemia rate on the combo vs 0.5% without in Trial 2 |
| Efavirenz (Sustiva, in Atripla) | Monitor Foundayo effectiveness; prescriber may escalate Foundayo dose | Label PBPK-simulated — Foundayo AUC ↓ 61%, Cmax ↓ 33% |
| Bosentan, Dabrafenib, Etravirine, Lorlatinib, Pexidartinib, Phenobarbital, Primidone, Sotorasib, Cenobamate | Monitor Foundayo effectiveness; prescriber may escalate dose | Label-precaution (moderate CYP3A4 inducers) |
| Modafinil (Provigil) | Monitor Foundayo effectiveness at higher modafinil doses | FDA table: weak CYP3A4 inducer at 200 mg/day; larger induction at 400 mg/day |
| Verapamil | Prescriber may monitor for side effects | Label PBPK-simulated — Foundayo AUC ↑ 2-fold |
| Diltiazem, grapefruit juice (high-concentration or daily) | Flag to prescriber; may monitor for side effects | Label-precaution (moderate CYP3A4 inhibitors) |
| Cyclosporine | Prescriber monitors for Foundayo side effects | Label-tested — Foundayo AUC ↑ 2.6-fold |
Tier 4A — Label-tested with no clinically relevant change
| Medication | Evidence |
|---|---|
| Atorvastatin (Lipitor) | Label-tested — “no clinically relevant changes were observed” |
| Rosuvastatin (Crestor) | Label-tested — “no clinically relevant changes were observed” |
| Esomeprazole (Nexium) | Label-tested — no effect on Foundayo exposure |
| Digoxin | Label-tested — 1.2-fold shift, not clinically meaningful |
| Midazolam | Label-tested — 1.1-fold shift; confirms Foundayo does not meaningfully affect most CYP3A4 substrates at usual doses |
| Acetaminophen (Tylenol) | Label-tested — delayed peak on first Foundayo dose (Cmax ↓ 28%), effect diminishes with repeated Foundayo dosing |
| Quinidine | Label-tested — no clinically meaningful change |
Tier 4B — Not specifically named in the Foundayo label
The following medication categories are not named in Foundayo’s interaction tables. That’s different from “cleared.” Lilly states Foundayo “has not been systematically studied with all medications.” Verify with your prescriber or pharmacist.
- Most antibiotics — azithromycin (Z-pak), amoxicillin, doxycycline, cephalosporins (Keflex), metronidazole (Flagyl), levofloxacin, ciprofloxacin (clarithromycin is the Tier 2 exception)
- Metformin
- Pravastatin, fluvastatin, pitavastatin (lovastatin is CYP3A4-sensitive like simvastatin — specifically ask your prescriber)
- Most blood pressure medications — ACE inhibitors (lisinopril), ARBs (losartan, valsartan), beta blockers (metoprolol, atenolol), thiazide diuretics, most calcium channel blockers (verapamil and diltiazem are Tier 3)
- Most antidepressants at label doses — SSRIs, SNRIs, bupropion, mirtazapine
- Most SGLT2 inhibitors (Jardiance, Farxiga), DPP-4 inhibitors (Januvia)
- Thyroid hormones (levothyroxine)
- NSAIDs (ibuprofen, naproxen)
- PPIs beyond esomeprazole (omeprazole, pantoprazole, lansoprazole) and H2 blockers — esomeprazole is directly tested; other acid reducers share the drug class but aren’t specifically named
- Vaccines — not named in interaction tables
The four-tier interaction map. Foundayo has not been systematically studied with all medications — always verify your full list with your prescriber or pharmacist.
Found your medication in Tier 1, 2, or 3?
Our free 60-second GLP-1 match quiz factors your medication list into the recommendation so you get a personalized path — not generic advice.
Check my GLP-1 path →Why Foundayo interacts with anything in the first place
Short answer: Foundayo has two separate interaction mechanisms. The first is metabolic — Foundayo runs through the liver’s CYP3A4 enzyme and two liver transporters (OATP1B1 and OATP1B3), so drugs that block or speed up those pathways change how much Foundayo is in your body. The second is digestive — Foundayo slows how fast your stomach empties, especially on the first dose, which can briefly shift how other swallowed medications are absorbed.
CYP3A4 is an enzyme that breaks down a huge share of prescription medications. If you take a drug that inhibits CYP3A4, Foundayo builds up higher than intended. If you take a drug that induces CYP3A4, Foundayo gets broken down too quickly and may not work well. OATP1B is a transporter that pulls certain drugs into the liver. Block both CYP3A4 and OATP1B simultaneously (what ritonavir does), and Foundayo exposure rises unpredictably — which is why ritonavir is the named avoid, not just a precaution.
Why this matters for you: the metabolic interactions are persistent as long as both drugs are in your system. The gastric-emptying interactions are temporary and most prominent at initiation or dose escalation. Different mechanisms, different management.
The gastric-emptying effect is different. In Foundayo’s own acetaminophen study, the Cmax of Tylenol dropped 28% after the very first Foundayo 0.8 mg dose, then diminished with repeated dosing. This is why oral hormonal contraceptives need a 30-day backup window on initiation and each dose increase — not because Foundayo is a persistent CYP inhibitor, but because it changes oral absorption timing during the escalation phase.
Does Foundayo affect birth control? The 30-day rule — with calendar
Short answer: If you take daily oral birth control pills, yes. Foundayo’s label tells you to use a non-oral method or add a barrier method for 30 days after starting Foundayo and 30 days after each dose increase. Non-oral methods — IUD, ring, patch, implant, injection — are not affected. Lilly did not clinically test Foundayo with oral contraceptives; this is a precautionary instruction based on gastric emptying.
The 30-day backup rule applies at initiation and at every dose increase. If you escalate monthly, backup may be needed continuously for the first 5–6 months.
The Foundayo contraception backup calendar
Foundayo’s standard escalation takes you from 0.8 mg → 2.5 mg → 5.5 mg → 9 mg → 14.5 mg → 17.2 mg, with at least 30 days on each dose. Here’s what the backup requirement looks like if you escalate on the earliest possible schedule:
| Month | Dose | Backup required? | Notes |
|---|---|---|---|
| Month 1 (days 1–30) | 0.8 mg | Yes — full 30 days | Starts the day of your first dose |
| Month 2 (days 31–60) | 2.5 mg | Yes — full 30 days | New window starts the day you bump up |
| Month 3 (days 61–90) | 5.5 mg | Yes — full 30 days | New window starts the day you bump up |
| Month 4 (days 91–120) | 9 mg | Yes — full 30 days | New window starts the day you bump up |
| Month 5 (days 121–150) | 14.5 mg | Yes — full 30 days | New window starts the day you bump up |
| Month 6 (days 151–180) | 17.2 mg | Yes — full 30 days | New window starts the day you bump up |
| Any month at the same dose (no escalation) | Same dose | No new backup window | Only triggers on dose increases |
Plain-English takeaway: If you escalate every 30 days, you’re essentially using backup continuously for the first 5–6 months. Switching to a non-oral method for the escalation phase and reassessing once you’ve hit your maintenance dose is one option worth discussing with your prescriber. IUDs, hormonal implants, the patch, the vaginal ring, and injectable Depo-Provera are all unaffected by Foundayo.
What counts as “backup”?
Per the label, you have two options:
- Switch to a non-oral hormonal method — IUD (Mirena, Kyleena, Liletta, Skyla, Paragard copper), implant (Nexplanon), ring (NuvaRing, Annovera), patch (Xulane, Twirla), injection (Depo-Provera). No backup needed with these.
- Add a barrier method to your pill — condoms are the label-consistent option. Keep taking your pill; condoms cover the 30-day windows.
Emergency contraception: The Foundayo label and Lilly’s medical interaction Q&A do not specifically address emergency contraception. If you need emergency contraception during a Foundayo backup window, call your pharmacist or healthcare provider the same day.
Can you take statins with Foundayo?
Short answer: Most statins are not dose-capped. Only simvastatin has a dose ceiling — 20 mg/day maximum. Atorvastatin and rosuvastatin are directly tested in the label with “no clinically relevant changes.” Here’s the twist most other pages miss: spacing simvastatin 2 hours apart from Foundayo doesn’t help. The label specifically tested that separation and the interaction still happened.
| Statin | Status | Evidence |
|---|---|---|
| Simvastatin (Zocor) | Capped at 20 mg/day | Label-tested — Foundayo doubled simvastatin acid; 2-hour staggering did not eliminate it |
| Atorvastatin (Lipitor) | No cap | Label-tested — “no clinically relevant changes were observed” |
| Rosuvastatin (Crestor) | No cap | Label-tested — “no clinically relevant changes were observed” |
| Pravastatin (Pravachol) | Not specifically named in the label | Metabolized independently of CYP3A4 |
| Fluvastatin (Lescol) | Not specifically named in the label | Metabolized via CYP2C9, not CYP3A4 |
| Pitavastatin (Livalo) | Not specifically named in the label | Minimal CYP3A4 involvement |
| Lovastatin (Mevacor) | Not specifically named in the label | CYP3A4-sensitive substrate like simvastatin; the Foundayo label does not set a cap, but specifically ask your prescriber |
Why simvastatin is the one that gets capped: simvastatin is a prodrug — your liver converts it into simvastatin acid, the active form. Foundayo’s clinical study showed a 2- to 2.5-fold increase in simvastatin acid exposure. At low simvastatin doses (≤20 mg/day), that’s manageable. At 40 or 80 mg, the risk of rhabdomyolysis and muscle injury rises.
If you’re already on simvastatin 40 mg: ask your prescriber about switching to atorvastatin or rosuvastatin before starting Foundayo. Both offer comparable LDL-lowering without the Foundayo simvastatin cap.
Foundayo with insulin or sulfonylureas: the hypoglycemia playbook
Short answer: Both combinations raise the risk of low blood sugar, but neither is a reason to stop Foundayo. The fix is a dose adjustment of the insulin or sulfonylurea, managed by your prescriber. In Lilly’s type 2 diabetes trial, hypoglycemia occurred in 7% of people on Foundayo with a sulfonylurea vs. 0.5% without one.
Foundayo lowers blood glucose on its own. Stack it on top of insulin or a sulfonylurea (which also lowers blood glucose), and the combined effect can drop you into hypoglycemia. One patient in Trial 2 on Foundayo 5.5 mg combined with a sulfonylurea had severe hypoglycemia; none on placebo did.
Sulfonylureas to watch for
- Glipizide (Glucotrol)
- Glimepiride (Amaryl)
- Glyburide (DiaBeta, Micronase, Glynase)
- Older agents: chlorpropamide, tolbutamide
Hypoglycemia symptoms to know cold
- Shakiness, sweating, dizziness
- Rapid heartbeat
- Sudden intense hunger
- Confusion, difficulty concentrating
- Headache, blurred vision
- Anxiety or irritability
What to keep on hand during the first month
- Glucose tablets (Dex4, TRUEplus) — 15 grams in your car, purse, and at work
- Juice box or regular soda (4 oz ≈ 15g of fast sugar)
- A CGM or fingerstick meter — the first 30 days on a new medication regimen is the highest-risk window
If blood sugar drops below 54 mg/dL and you can’t get it back up within 15 minutes of eating fast sugar, call your care team. If you can’t safely eat or you lose consciousness, that’s 911.
Which antibiotics, antifungals, and HIV meds matter?
Short answer: Most antibiotics are not named in Foundayo’s interaction tables. Clarithromycin is the exception — it requires capping Foundayo at 9 mg/day. HIV regimens containing ritonavir (and Paxlovid for COVID-19) are the category that’s a straight avoid — ritonavir inhibits both CYP3A4 and OATP1B.
Antibiotics
| Antibiotic | Action needed | Why |
|---|---|---|
| Azithromycin (Z-pak) | Not named in the Foundayo label interactions table | Not a CYP3A4 inhibitor |
| Amoxicillin, amoxicillin/clavulanate (Augmentin) | Not named in the Foundayo label interactions table | Not a CYP3A4 interactor |
| Doxycycline | Not named in the Foundayo label interactions table | Not a CYP3A4 interactor |
| Cephalosporins (Keflex, cephalexin) | Not named in the Foundayo label interactions table | Not a CYP3A4 interactor |
| Metronidazole (Flagyl) | Not named in the Foundayo label interactions table | Not a CYP3A4 interactor |
| Clarithromycin (Biaxin) | Cap Foundayo at 9 mg/day | Strong CYP3A4 inhibitor — Foundayo AUC ↑ 3.5-fold |
| Erythromycin | Prescriber may monitor | Moderate CYP3A4 inhibitor |
| Ciprofloxacin, levofloxacin | Not named in the Foundayo label interactions table | CYP1A2 inhibitors, not CYP3A4 |
| Rifampin (and rifaximin, rifabutin) | Avoid rifampin | Strong CYP3A4 inducer — cuts Foundayo effectiveness |
Antifungals
- Fluconazole (Diflucan) — moderate CYP3A4 inhibitor; prescriber may monitor, not formally dose-capped on the Foundayo label
- Itraconazole, ketoconazole (oral), posaconazole, voriconazole — strong CYP3A4 inhibitors — cap Foundayo at 9 mg/day while on them
- Terbinafine (Lamisil) — CYP2D6 inhibitor, not CYP3A4; not named in the Foundayo label
- Nystatin, clotrimazole (topical) — topical-only, negligible systemic absorption
HIV and COVID antivirals
- Any ritonavir-containing regimen — Kaletra, Norvir, boosted protease inhibitors, cobicistat-boosted regimens that include ritonavir — avoid. Ritonavir inhibits both CYP3A4 and OATP1B. The dual block makes Foundayo exposure rise unpredictably.
- Paxlovid (nirmatrelvir/ritonavir) — same mechanism. If you’re prescribed Paxlovid for COVID-19 while on Foundayo, ask your prescriber about the right approach — this is a clinician decision, not a patient one. The Foundayo label states to avoid ritonavir-containing regimens but does not publish a specific Paxlovid hold protocol.
- Efavirenz (Sustiva, Atripla) — Foundayo AUC drops 61% per label PBPK simulation. Monitor effectiveness; your prescriber may need to escalate your Foundayo dose further or switch your HIV regimen.
- Integrase inhibitors without ritonavir (dolutegravir, bictegravir-based regimens like Biktarvy) — not specifically named in the Foundayo label interactions table.
On a Tier 1 regimen? Injectable GLP-1s — Zepbound (tirzepatide), Wegovy (semaglutide), Ozempic — are peptides, not small molecules. They don’t route through CYP3A4. Your seizure medication or HIV regimen doesn’t interfere with them. Compare Foundayo vs Ozempic
The damaging admission — who Foundayo isn’t the right fit for
Every page trying to sell you something glosses over this. We won’t.
Foundayo is not the easy yes if you take a strong CYP3A4 inducer every day. If you’re on carbamazepine for seizures, phenytoin for epilepsy, rifampin for tuberculosis, or enzalutamide for prostate cancer, Foundayo’s clinical effectiveness drops substantially — in carbamazepine’s case, Lilly’s own data showed an 82% AUC reduction. The drug may not do its job.
If that’s you, here’s the good news: Foundayo is the only major daily oral GLP-1 with this CYP3A4 sensitivity. Weekly injectable GLP-1s — Ozempic, Wegovy, Zepbound, Mounjaro — are peptides, not small molecules, and they don’t route through CYP3A4. Your seizure medication doesn’t interfere with them.
Because Foundayo is an oral small molecule, readers who aren’t on strong CYP3A4 inducers get what no injectable offers: no needles, no refrigeration, no sharps disposal, take it any time with or without food.
Usually a poor fit for Foundayo:
- Daily carbamazepine, phenytoin, rifampin, or any strong CYP3A4 inducer
- Long-term ritonavir-containing HIV regimens
- Anyone already on another GLP-1 without a plan to switch
Can you take Foundayo with Ozempic, Wegovy, Zepbound, or Mounjaro?
No. Foundayo’s FDA-approved label explicitly states that concomitant use with another GLP-1 receptor agonist is not recommended. If you’re switching from another GLP-1 to Foundayo, your prescriber will stop the first one before starting Foundayo. There’s no benefit to stacking them, and GI side effects compound.
The “not recommended” group includes every GLP-1 or GLP-1/GIP combo currently on the market: semaglutide (Ozempic, Wegovy, Rybelsus), tirzepatide (Mounjaro, Zepbound), liraglutide (Victoza, Saxenda), dulaglutide (Trulicity), exenatide (Byetta, Bydureon), and any compounded semaglutide or tirzepatide.
The Foundayo label says concomitant use is not recommended but does not publish specific washout windows by prior GLP-1. Ask your prescriber specifically what day to take your first Foundayo dose — don’t improvise on the timing yourself.
Foundayo before surgery or anesthesia
Short answer: Tell your surgical team you’re on Foundayo as soon as the procedure is scheduled, and follow their instructions exactly. Foundayo slows gastric emptying, which has been linked to rare cases of pulmonary aspiration during general anesthesia or deep sedation even when patients followed fasting rules. Foundayo’s label states that available data are insufficient to make specific recommendations about modifying fasting or temporarily holding Foundayo, so your anesthesiologist makes the call.
GLP-1 medications have been under active anesthesia-society review since 2023. Your anesthesiologist is making a judgment call based on your procedure, your current Foundayo dose, and current professional guidance — not a hard Foundayo-specific rule published in the label.
What to tell them
- 1. You take Foundayo (orforglipron)
- 2. Your current dose and how long you’ve been on it
- 3. Your last dose before the scheduled procedure
- 4. Any GI symptoms you’ve had recently (bloating, reflux, delayed fullness)
Don’t stop, hold, or time Foundayo on your own without coordinating with the team managing the procedure — your prescriber and anesthesiologist should be aligned.
Foundayo and alcohol, grapefruit, and supplements
Short answer: Foundayo’s label does not define a formal alcohol interaction; consumer drug references describe alcohol effects as unknown. Grapefruit juice is a moderate CYP3A4 inhibitor; Foundayo’s label doesn’t specifically address it but the general CYP3A4 logic applies. St. John’s Wort is a strong CYP3A4 inducer and belongs on the Tier 1 avoid list.
Alcohol
The Foundayo label does not name a formal alcohol interaction. “Unknown” is not a green light — it’s an honest acknowledgment that Lilly didn’t run a clinical alcohol study. What we do know:
- Alcohol can worsen nausea, vomiting, and other GI side effects
- Heavy alcohol use raises pancreatitis risk (pancreatitis is a Foundayo warning/precaution; the boxed warning is thyroid C-cell tumors)
- Alcohol can drop blood glucose hours after drinking — relevant if you’re also on insulin or a sulfonylurea
Grapefruit juice
FDA classifies grapefruit juice as a moderate CYP3A4 inhibitor — and sometimes a strong one depending on preparation and concentration. The Foundayo label does not specifically address grapefruit. If grapefruit is a regular part of your diet, flag it to your prescriber. Listed in Tier 3 above.
St. John’s Wort
A hard avoid. The FDA classifies St. John’s Wort as a strong CYP3A4 inducer — same mechanism as carbamazepine. It’s sold as a mood supplement, often without a prescription. Taking St. John’s Wort with Foundayo is expected to significantly cut Foundayo’s effectiveness.
Other supplements
Foundayo has not been systematically studied with most supplements. Specific supplements often asked about — turmeric/curcumin, black pepper extract, echinacea, kava, valerian, CBD, berberine — are not named in Foundayo’s interaction tables. Bring your complete supplement list to your prescriber or pharmacist and ask them to run it against the FDA CYP3A4 table.
If you take X, is Foundayo still a fit?
Short answer: Most medication lists don’t disqualify Foundayo — they require planning. The real split is between lists that need an adjustment (oral birth control, simvastatin, insulin, sulfonylurea) and lists that make Foundayo a poor mechanical fit (daily strong CYP3A4 inducers, ritonavir-containing regimens).
Usually workable with planning
- Oral birth control → backup contraception
- Simvastatin → cap or switch
- Insulin or sulfonylurea → prescriber manages dose
- Atorvastatin, rosuvastatin, esomeprazole, acetaminophen → label-tested, no issue
- Most unlisted medications → verify with prescriber
Needs clinician input before starting
- Clarithromycin, ketoconazole, itraconazole → 9 mg cap
- Verapamil, diltiazem → monitored
- Moderate CYP3A4 inducers → may need dose escalation
- Cyclosporine → coordinate with transplant team
Usually a poor fit for Foundayo
- Daily carbamazepine, phenytoin, rifampin
- Long-term ritonavir-containing HIV regimens
- Already on another GLP-1 without a switch plan
How to talk to your prescriber before your first Foundayo dose
Short answer: Send your prescriber or pharmacist a single message that names every medication you take, identifies the Foundayo interaction bucket each one falls into, and asks for a clear next action.
The medication review message template
Copy, paste, fill in the blanks, send to your prescriber or pharmacy portal.
Questions to ask your pharmacist when picking up Foundayo
- 1. “Have you run my full medication list against the Foundayo label?”
- 2. “Is there anything about my list that should change my starting dose or my escalation?”
- 3. “If I’m prescribed an antibiotic or antifungal in the next year, which ones do I need to flag to the prescribing doctor as a potential Foundayo interaction?”
- 4. “What does my insurance plan cover if I need to switch simvastatin to atorvastatin because of Foundayo?”
What to bring to your first Foundayo appointment
- A written list of every prescription medication, dose, and frequency
- A list of every over-the-counter medication and supplement — including vitamins, protein powders, and herbal products
- Your current A1C, BMI, and blood pressure if you know them
- A note about pregnancy plans and your current contraception method
- A list of upcoming surgeries or dental procedures
If you’re not on Foundayo yet — the affordability shortcut
Short answer: Foundayo’s regular self-pay price ranges from $149 to $349 per month depending on dose. Commercially insured patients with coverage may pay as little as $25/month via Lilly’s savings card. A separate Medicare Part D bridge pathway makes Foundayo available for $50/month for eligible beneficiaries starting July 1, 2026. The bottleneck for most people isn’t finding a prescriber — it’s getting insurance to approve Foundayo, which usually requires prior authorization paperwork. Telehealth providers with insurance concierge services handle that paperwork.
Foundayo price by pathway — verified April 22, 2026
| Pathway | Who qualifies | Monthly cost | Source |
|---|---|---|---|
| Lilly regular self-pay (LillyDirect) | Anyone with a prescription | $149 / $199 / $299 / $349 by dose | foundayo.lilly.com/coverage-savings |
| Commercial insurance with Foundayo coverage + Lilly savings card | Commercially insured, plan covers Foundayo | As low as $25/month | foundayo.lilly.com/coverage-savings |
| Commercial insurance without Foundayo coverage + Lilly savings | Commercially insured, plan doesn’t cover Foundayo | $149 / $199 / $299 by dose | foundayo.lilly.com/coverage-savings |
| Medicare Part D bridge/demo pathway | Eligible Medicare Part D beneficiaries, starting July 1, 2026 | $50/month | CMS Medicare Part D demonstration |
See if you qualify for Foundayo and what you’d actually pay
Ro is a telehealth provider that publicly offers FDA-approved Foundayo, runs a free GLP-1 Insurance Coverage Checker that shows what you’d actually pay, and has a dedicated insurance concierge team that handles prior authorization paperwork — which is the real bottleneck for most people.
Check eligibility on Ro →Disclosure: The RX Index may earn a commission when readers sign up via affiliate links. This never affects the clinical guidance above — every interaction tier on this page traces to the Foundayo FDA label and the FDA’s CYP table.
Who Ro is right for: you want FDA-approved Foundayo, you want someone to handle the insurance paperwork, and you’d rather not find your own prescriber cold. Who Ro isn’t right for: you already have a prescriber you trust and just need a pharmacy — in that case, LillyDirect is simpler.
Frequently asked questions
What medications cannot be taken with Foundayo?
The Foundayo FDA label tells you to avoid strong CYP3A4 inducers (carbamazepine, phenytoin, rifampin, St. John’s Wort, enzalutamide, mitotane, apalutamide), ritonavir-containing regimens including Paxlovid and most boosted HIV therapies, and any other GLP-1 receptor agonist.
Does Foundayo interact with birth control pills?
Yes — in a precautionary way. Foundayo’s label tells people taking oral hormonal contraceptives to use a non-oral method (IUD, ring, patch, implant, injection) or add a barrier method for 30 days after starting Foundayo and 30 days after each dose increase. Non-oral hormonal methods are not affected.
Can I take Tylenol (acetaminophen) with Foundayo?
Yes. Foundayo’s label directly tested this. Acetaminophen’s peak blood level dropped 28% after the first Foundayo dose, then the effect diminished with repeated dosing. The label does not list acetaminophen as a dose-limited combination.
Does Foundayo affect my thyroid medication?
Levothyroxine is not specifically named in the Foundayo label interactions table. If you’re concerned about changes to thyroid symptoms during your first months on Foundayo, raise it with your prescriber so they can decide whether a TSH check is warranted.
Can I drink alcohol on Foundayo?
Foundayo’s label doesn’t define a formal alcohol interaction. Alcohol can worsen GI side effects, raise pancreatitis risk, and drop blood glucose (risky if you’re also on insulin or a sulfonylurea). Talk to your prescriber about your specific situation.
Does Foundayo interact with blood pressure medications?
Most aren’t named in Foundayo’s interaction table. Verapamil and diltiazem are moderate CYP3A4 inhibitors and may raise Foundayo exposure — monitored but not dose-capped on the label. ACE inhibitors (lisinopril), ARBs (losartan, valsartan), beta blockers (metoprolol, atenolol), thiazide diuretics, and amlodipine are not named in the Foundayo label interactions table.
Can I take Foundayo with Ozempic, Wegovy, Zepbound, or Mounjaro?
No. Foundayo’s label states that concomitant use with another GLP-1 receptor agonist is not recommended. If you’re switching to Foundayo from another GLP-1, your prescriber will have you stop the previous medication before your first Foundayo dose.
Does Foundayo affect atorvastatin or rosuvastatin?
Both are directly tested in the Foundayo label. For atorvastatin and rosuvastatin, the label states “no clinically relevant changes were observed.” Only simvastatin has a dose ceiling (20 mg/day).
How long before surgery should I stop Foundayo?
Tell your surgical team you take Foundayo as soon as your procedure is scheduled. Foundayo’s label states available data are insufficient to make specific recommendations about modifying fasting or temporarily holding Foundayo. Follow your surgical team’s instructions exactly.
Is grapefruit safe with Foundayo?
The Foundayo label doesn’t specifically address grapefruit. FDA classifies grapefruit juice as a moderate CYP3A4 inhibitor whose effect varies widely by preparation and concentration. If grapefruit is a regular part of your diet, flag it to your prescriber.
What if I miss 7 or more doses of Foundayo in a row?
Don’t restart at your previous dose. The Foundayo label specifically says if 7 or more consecutive doses are missed, restart the dose escalation at a lower dose to reduce GI side effects. Contact your prescriber.
Do I need to separate Foundayo from my other pills by 2 hours?
For simvastatin, no — the Foundayo label specifically tested 2-hour separation and the interaction still happened. For other medications, the label doesn’t publish a blanket spacing rule. If you take a narrow-therapeutic-window oral medication (warfarin, levothyroxine, seizure meds, lithium, immunosuppressants), ask your prescriber or pharmacist whether any specific timing precaution applies.
Does Foundayo interact with vaccines?
Vaccines are not named in Foundayo’s interaction tables. Foundayo is not expected to affect your immune response to routine vaccinations.
Related Foundayo guides
Still not sure which GLP-1 program is right for you?
You’ve seen the interaction map. You know which tier your medications fall into. If you’re still unsure whether Foundayo fits your specific medication list, goal, and insurance situation — take the quiz. 60 seconds, free, personalized.
Take the free 60-second GLP-1 matching quiz →Sources
- 1 FOUNDAYO (orforglipron) US Prescribing Information, Eli Lilly and Company, revised April 2026 — DailyMed Set ID
8ac446c5-feba-474f-a103-23facb9b5c62. dailymed.nlm.nih.gov - 2 FDA — For Healthcare Professionals: FDA’s Examples of Drugs that Interact with CYP Enzymes and Transporter Systems, current as of January 20, 2026. fda.gov
- 3 Eli Lilly Medical — “Does Foundayo (orforglipron) interact with other medications?” HCP answer portal. medical.lilly.com
- 4 Foundayo FDA-Approved Medication Guide, Eli Lilly, April 2026. dailymed.nlm.nih.gov
- 5 FDA Press Release — FDA approves Foundayo, April 1, 2026. fda.gov
- 6 Foundayo Coverage & Savings page, Eli Lilly, current as of April 22, 2026. foundayo.lilly.com
- 7 LillyDirect — Foundayo pharmacy page, current as of April 22, 2026. lilly.com/lillydirect
- 8 Ro — Foundayo product and pricing page, current as of April 22, 2026. ro.co/weight-loss/foundayo
Written by The RX Index Editorial Team. The RX Index is a pricing intelligence and comparison resource for GLP-1 telehealth providers. This article is informational and does not constitute medical advice. Speak with a licensed healthcare provider before starting, changing, or stopping any prescription medication. Last verified: April 22, 2026.