The 2022 American Gastroenterological Association (AGA) guideline on pharmacological interventions for obesity notes that glucagon-like peptide 1 (GLP-1) receptor agonists, including semaglutide and liraglutide, delay gastric emptying, and explicitly states that this effect may impact the absorption of some oral medications that require rapid onset of action. However, the guideline does not provide drug-specific pharmacokinetic data or identify particular medications affected. [1]
A 2024 systematic review assessed drug-drug interactions between GLP-1 receptor agonists (GLP-1RAs) and oral medications and included 22 reports and 6 prescribing sheets, finding that GLP-1RAs slow gastric emptying and result in reduced or unchanged Cmax and delayed Tmax across multiple drug classes including warfarin, contraceptive pills, acetaminophen, statins, (angiotensin converting enzyme) ACE inhibitors, and digoxin; however, overall exposure (AUC) was generally unchanged and no clinically significant differences in pharmacokinetic or pharmacodynamic outcomes were observed. The authors noted that the known effect of GLP-1RAs to slow gastric motility has raised concerns regarding potential changes in oral drug absorption; however, to date, no clinically significant effect has been observed for any of the evaluated oral medications, and dose adjustments are probably not required for simultaneous use of GLP-1RAs with oral medications, though these findings should be interpreted cautiously in patients with gastroparesis, kidney dysfunction, or when coadministering drugs with a narrow therapeutic index. [2]
A 2025 comprehensive review provided an extensive analysis of the pharmacokinetics and drug-drug interactions (DDIs) of GLP-1 RAs and the dual GLP-1/glucose-dependent insulinotropic polypeptide (GIP) receptor agonist, tirzepatide. This review examined the pharmacokinetic profiles of five peptide-derived incretin mimetic medications, including exenatide, liraglutide, dulaglutide, semaglutide, and tirzepatide, highlighting the structural modifications employed to extend their half-lives and improve their therapeutic efficacy. The review highlighted the current understanding of pharmacokinetic DDIs associated with GLP-1 RAs and tirzepatide, noting an absence of clinically significant interactions mediated by metabolic enzymes or transporters. Nevertheless, mechanism-of-action-mediated DDIs, particularly those related to delayed gastric emptying, have been identified, with certain interactions with oral contraceptives and levothyroxine being noteworthy. Studies assessing drug interactions with GLP-1 RAs indicate that delayed gastric emptying can alter the absorption of some orally administered drugs, particularly those with narrow therapeutic indices. Most drugs, including digoxin and warfarin, show minimal changes in pharmacokinetics, though postmarketing reports with exenatide suggest occasional increases in INR. Oral semaglutide has been shown to delay levothyroxine absorption, decreasing Cmax by 12% and increasing AUC by 33%, and oral contraceptives may also be affected, highlighting potential clinical relevance. Administering these medications at least one hour before GLP-1 RA dosing and close monitoring of therapeutic effects is advised, as delayed gastric emptying may diminish with repeated dosing, but the possibility of clinically significant interactions cannot be excluded. Despite the extensive investigation, the authors acknowledged that further research is necessary to fully comprehend and mitigate the risks associated with these therapies, ensuring safe and effective concurrent medication use. [3]
A 2019 single-author review evaluated pharmacologically relevant drug interactions of GLP-1 receptor agonists and reported that delayed gastric emptying may slow the absorption of several orally administered medications, including acetaminophen, digoxin, warfarin, oral contraceptives, metformin, statins, ACE inhibitors, and griseofulvin. Concomitant use resulted in delayed absorption (eg, delayed tmax) for acetaminophen, digoxin, warfarin, oral contraceptives, statins, ACE inhibitors, and griseofulvin; however, these changes were described as minimal and not clinically significant, and no dose adjustments were required. Warfarin INR was not significantly affected, though monitoring was recommended due to the narrow therapeutic index. An increased risk of hypoglycemia was observed with coadministration of GLP-1 receptor agonists and sulfonylureas or insulin, requiring dose adjustment of these agents. Overall, the review reported that while absorption of several oral medications may be delayed, pharmacokinetics were not meaningfully altered, and interactions were generally not clinically significant; moreover, delayed absorption may be minimized by administering oral medications at least 1 hour prior to GLP-1 receptor agonist administration. [4]
A 2012 review examined drug interaction studies involving GLP-1RAs such as exenatide, liraglutide, albiglutide, and lixisenatide alongside concurrent oral medications. From a pool of 254 potentially relevant articles, 11 were selected for detailed analysis, encompassing 15 different drug interactions. Among the interactions studied, the majority demonstrated equivalence in the area under the concentration-time curve (AUC), except for notable reductions in AUC observed with acetaminophen and lovastatin following exenatide administration, as well as decreased AUCs for lisinopril and digoxin with liraglutide. The findings outlined in the review highlight the potential for clinically significant interactions between GLP-1RAs and drugs requiring precise peak concentrations or rapid onset of action. The review emphasized that while GLP-1RAs generally did not affect the overall drug exposure for most medications, they consistently led to a decrease in maximum concentration (Cmax) and a prolongation of the time to reach maximum concentration (tmax) in the majority of cases. The implications of these interactions are particularly critical for medications requiring rapid absorption and effect. The review calls for further research, particularly in patients with type 2 diabetes, to better assess the pharmacokinetic and pharmacodynamic impacts of GLP-1RAs in combination with oral medications, highlighting the need for placebo-controlled studies across various GLP-1RAs to ensure comprehensive evaluation within this therapeutic class. [5]
A 2025 physiologically based pharmacokinetic (PBPK) analysis evaluated the impact of GLP-1 receptor agonist–induced delays in gastrointestinal motility on the pharmacokinetics of coadministered oral medications using a simulation model in a virtual cohort of obese adults (N= 1,000), incorporating gastric emptying delays based on clinical data from liraglutide-treated patients. The analysis found that GLP-1RA-related delays increased AUC and prolonged Tmax for several drugs, including atorvastatin, metformin, metoprolol, ethinyl estradiol, and digoxin, with model outputs generally consistent with available clinical data. Exploratory analyses of commonly coadministered medications demonstrated larger increases in drug exposure, with AUC increases of 64% for rosuvastatin, 90% for valsartan, and 205% for dabigatran, along with delayed Tmax across these agents; dabigatran, a narrow therapeutic index anticoagulant, showed the greatest change in exposure. Sensitivity analyses indicated that small intestinal transit time primarily influenced AUC and overall drug exposure, while gastric emptying time primarily influenced Tmax. The authors concluded that GLP-1RAs can influence the pharmacokinetics of oral medications by delaying gastric emptying, potentially leading to clinically relevant drug–drug interactions, though further clinical validation is needed. [6]
Additional studies examining GLP-1RAs suggest a consistent pattern of delayed gastric emptying affecting oral drug absorption. Research on dulaglutide in healthy subjects found that coadministration with digoxin, warfarin, atorvastatin, and oral contraceptives caused a delay in time to maximum plasma concentration (Tmax) across all drugs, with minimal effects on overall exposure (AUC) and no clinically meaningful impact on efficacy or pharmacodynamics. Similarly, liraglutide was shown to delay Tmax and reduce peak concentrations (Cmax) for drugs such as atorvastatin, lisinopril, and digoxin, while overall exposure remained largely unchanged; griseofulvin showed an increase in Cmax without changes in AUC. Both sets of findings indicate that GLP-1RAs can alter the rate, but not substantially the extent, of absorption for coadministered oral medications, generally without necessitating dose adjustments. [7], [8]