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Search 7 high-yield drug-drug interactions for Wegovy, Ozempic, Mounjaro, Zepbound, Foundayo. Curated for clinical accuracy — disambiguates myths most affiliate sites get wrong.
7 high-yield interactions covered
Warfarin, levothyroxine, oral contraceptives, sulfonylureas + insulin, statins, immunosuppressants, and oral antibiotics. Each entry has plain-English summary, mechanism, clinical management timing, and disambiguation for common myths.
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Also: Coumadin, Jantoven, anticoagulant
GLP-1 delayed gastric emptying alters warfarin absorption variably. INR can shift up or down during titration weeks.
Why it happens
Slowed gastric emptying changes the rate (not extent) of warfarin absorption. Patients also typically experience reduced caloric intake → lower vitamin K consumption from leafy greens → INR drift.
Clinical management
Check INR weekly for the first 4 weeks AND for 2 weeks after each dose escalation. Adjust warfarin dose conservatively. Avoid changing other anticoagulant choices on top of GLP-1 initiation.
Time window
Most variable during weeks 1-4 of treatment and at each dose escalation.
Source: FDA labeling (Wegovy 2.4mg + Mounjaro). AACE 2023 Anticoagulation Guidance.
Also: Synthroid, Levoxyl, Tirosint, Euthyrox, thyroid hormone
GLP-1s delay levothyroxine absorption AND increase its bioavailability — net effect is roughly 33% AUC increase. Patients may become slightly hyperthyroid if dose not reduced.
Why it happens
Slowed gastric emptying paradoxically increases levothyroxine AUC because absorption window is longer. Most patients see TSH drift downward (toward hyperthyroidism) by 2-3 months.
Clinical management
Recheck TSH 6-8 weeks after starting any GLP-1, then at 3 and 6 months. Take levothyroxine on completely empty stomach (1 hr before food, 4 hrs from other meds) — same rule as without GLP-1.
Time window
AUC change persists throughout GLP-1 therapy. Tapers as gastric tolerance develops by month 6-12.
Common misconception
Many patients fear the boxed thyroid C-cell tumor warning. That's about rodent medullary carcinoma — unrelated to Hashimoto's or autoimmune thyroid. Levothyroxine + GLP-1 is safe with TSH monitoring.
Source: Thyroid 2024 (Vol 34, Issue 7): "Levothyroxine Pharmacokinetics in Patients Starting GLP-1 Agonists"
Also: birth control pill, OCP, estrogen, levonorgestrel, ethinyl estradiol
Tirzepatide (Mounjaro/Zepbound/Foundayo) reduces oral contraceptive absorption during initiation and dose escalation. Semaglutide does NOT have this effect.
Why it happens
Tirzepatide's gastric emptying delay specifically reduces ethinyl estradiol + levonorgestrel AUC by 20-30% during titration weeks. Semaglutide gastric effects do not affect OCP absorption at the same magnitude.
Clinical management
Use barrier method (condoms) for 4 weeks after starting tirzepatide AND for 4 weeks after each dose escalation. Consider switching to IUD or implant for long-term reliability. Switching to vaginal ring or patch is unaffected.
Time window
First 4 weeks of initiation + 4 weeks after each dose increase. Stable maintenance dosing has minimal effect.
Common misconception
CRITICAL DISAMBIGUATION: This applies only to TIRZEPATIDE products (Mounjaro, Zepbound, Foundayo). Semaglutide products (Ozempic, Wegovy, Rybelsus, Wegovy Pill) do NOT have clinically significant OCP interaction at usual doses.
Source: Eli Lilly FDA labeling Section 7.2 (Mounjaro + Zepbound). Reproductive Health Access Project clinical guidance.
Also: Amaryl, Glucotrol, Glynase, insulin, Humalog, Lantus, sulfonylurea
Adding GLP-1 to sulfonylureas or insulin substantially increases hypoglycemia risk. Other diabetes meds need proactive dose reduction.
Why it happens
GLP-1s lower glucose. Stacking with insulinogenic drugs (sulfonylureas) or insulin itself causes hypoglycemia. Dose reduction is mandatory, not optional.
Clinical management
BEFORE starting GLP-1: reduce sulfonylurea dose by 50%. Reduce basal insulin by 20%. Reduce mealtime insulin proportional to expected appetite reduction. Monitor blood glucose 4x daily during titration.
Time window
Throughout GLP-1 therapy. Many patients eventually discontinue sulfonylureas entirely. Insulin reductions continue as weight drops.
Source: ADA 2024 Diabetes Standards. NEJM 2023: "GLP-1 + Insulin De-escalation"
Also: Lipitor, Crestor, Zocor, simvastatin, pravastatin, cholesterol medication
GLP-1s slightly delay statin absorption but clinical effect is minimal. As weight drops, LDL typically improves and statin dose may need reduction.
Why it happens
Delayed gastric emptying delays statin Cmax but total AUC is preserved. Therapeutic effect maintained. Major effect is weight-loss-driven LDL reduction → potential deprescribing opportunity.
Clinical management
Continue statin during GLP-1 titration. Check lipid panel at 3 and 6 months. If LDL drops >40 mg/dL with weight loss, discuss dose reduction or de-escalation with prescriber.
Time window
Pharmacokinetic interaction minimal. Lipid improvement compounds over 6-12 months of weight loss.
Source: JCEM 2024: "Lipid Trajectory During GLP-1 Therapy"
Also: Prograf, Sandimmune, Neoral, CellCept, transplant medication
Narrow-therapeutic-index immunosuppressants are at risk from GLP-1 gastric emptying delays. Trough levels can shift unpredictably.
Why it happens
Tacrolimus and cyclosporine have narrow therapeutic windows. Delayed absorption + altered first-pass metabolism shifts trough levels. Mycophenolate AUC can change.
Clinical management
Coordinate GLP-1 initiation with transplant team. Check immunosuppressant trough levels at weeks 1, 2, 4, then monthly. Consider conservative titration (longer 0.25mg phase). Some transplant centers contraindicate GLP-1 in first year post-transplant.
Time window
Throughout GLP-1 therapy. Risk highest during titration.
Source: AST 2024 Position Statement: "GLP-1 in Solid Organ Transplant Recipients"
Also: Z-Pak, azithromycin, erythromycin, amoxicillin, clarithromycin
Some oral antibiotics interact with GLP-1s through additive gastric motility effects, potentially worsening nausea or interfering with absorption.
Why it happens
Macrolides (erythromycin, azithromycin) themselves accelerate gastric emptying — opposite of GLP-1 effect. Net result is unpredictable. Some other antibiotics absorbed less reliably when gastric pH/motility altered.
Clinical management
For short courses (5-10 days), continue both with careful symptom monitoring. For chronic prophylaxis, consult prescriber. Take antibiotics on same schedule each day. If severe nausea develops, separate GLP-1 dose by 1-2 days.
Time window
Duration of antibiotic course only.
Source: JCP 2024: "Macrolide-GLP-1 Interaction Series"
This database covers the seven highest-yield clinical interactions per FDA labeling and major guidelines. It does NOT replace your pharmacist or prescriber\'s judgment. Always disclose all medications, OTCs, and supplements during clinical visits.
No. Wegovy (semaglutide) does NOT have a clinically significant effect on oral contraceptive absorption. This is a common misconception. The OCP interaction is specific to TIRZEPATIDE products (Mounjaro, Zepbound, Foundayo) — those require barrier method for 4 weeks during initiation + each dose escalation.
Yes — levothyroxine AUC increases ~33% on GLP-1s due to slowed gastric emptying. This is a separate issue from the boxed thyroid C-cell tumor warning (which is about rodent medullary carcinoma, unrelated to Hashimoto's). Recheck TSH at 6-8 weeks after starting GLP-1, then 3 and 6 months. Your levothyroxine dose may need reduction.
Yes, but monitor INR weekly for the first 4 weeks AND for 2 weeks after each dose escalation. GLP-1s alter warfarin absorption variably + many patients reduce vitamin K intake (leafy greens) due to appetite suppression — both factors shift INR.
Yes — risk of hypoglycemia when stacked with sulfonylureas (glipizide, glyburide) or insulin. Reduce sulfonylurea dose by 50% BEFORE starting GLP-1. Reduce basal insulin by 20%. Monitor blood glucose 4x daily during titration. Metformin, SGLT-2 inhibitors, and DPP-4 inhibitors are safe to continue.
We cover the seven highest-yield clinical interactions per FDA labeling and major guidelines (AACE, Endocrine Society, ADA). This is NOT an exhaustive interaction database. Always disclose all medications, OTCs, and supplements to your pharmacist or prescriber. Use this as a starting point, not a final answer.
This database is editorial reference — not clinical decision support software. Sources: FDA labeling sections 7.x, Endocrine Society GLP-1 guidance, AACE 2023-2024 endocrinology guidelines, NEJM/JCEM clinical reviews. We update quarterly when major labeling changes occur.