Drug Interactions between acetaminophen / caffeine / dihydrocodeine and tirzepatide

GENERALLY AVOID: Chronic, excessive consumption of alcohol may increase the risk of acetaminophen-induced hepatotoxicity, which has included rare cases of fatal hepatitis and frank hepatic failure requiring liver transplantation. The proposed mechanism is induction of hepatic microsomal enzymes during chronic alcohol use, which may result in accelerated metabolism of acetaminophen and increased production of potentially hepatotoxic metabolites.

MANAGEMENT: In general, chronic alcoholics should avoid regular or excessive use of acetaminophen. Alternative analgesic/antipyretic therapy may be appropriate in patients who consume three or more alcoholic drinks per day. However, if acetaminophen is used, these patients should be cautioned not to exceed the recommended dosage (maximum 4 g/day in adults and children 12 years of age or older).

MONITOR: Glucagon-like peptide-1 (GLP-1) receptor agonists and dual GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) receptor agonists can delay gastric emptying, which may impact the absorption of concomitantly administered oral medications. Mild to moderate decreases in plasma concentrations of coadministered drugs have been demonstrated in pharmacokinetic studies for some GLP-1 receptor agonists (e.g., exenatide, lixisenatide), but not others. According to the prescribing information, liraglutide did not affect the absorption of several orally administered drugs to any clinically significant extent, including acetaminophen, atorvastatin, digoxin, griseofulvin, lisinopril, and an oral contraceptive containing ethinyl estradiol-levonorgestrel. Likewise, no clinically relevant effect on absorption was observed for concomitantly administered oral drugs studied with albiglutide (digoxin, ethinyl estradiol-norethindrone, simvastatin, warfarin), dulaglutide (acetaminophen, atorvastatin, digoxin, ethinyl estradiol-norelgestromin, lisinopril, metformin, metoprolol, sitagliptin, warfarin), or semaglutide (atorvastatin, digoxin, ethinyl estradiol-levonorgestrel, metformin, warfarin). The impact of dual GLP-1 and GIP receptor agonist tirzepatide on gastric emptying was reported to be dose- and time-dependent, with the greatest effect observed after a single 5 mg dose but diminished after subsequent doses. When acetaminophen was administered following a single 5 mg dose of tirzepatide, acetaminophen peak plasma concentration (Cmax) was decreased by 50% and its median time to peak plasma concentration (Tmax) delayed by 1 hour. However, no significant impact on acetaminophen Cmax and Tmax was observed after 4 consecutive weekly doses of tirzepatide (5 mg/5 mg/8 mg/10 mg), and the overall exposure (AUC) of acetaminophen was unaffected. Tirzepatide at lower doses of 0.5 mg and 1.5 mg also had minimal effects on acetaminophen exposure.

MANAGEMENT: Although no specific dosage adjustment of concomitant medications is generally recommended based on available data, potential clinical impact on some oral medications cannot be ruled out, particularly those with a narrow therapeutic index or low bioavailability, those that depend on threshold concentrations for efficacy (e.g., antibiotics), and those that require rapid gastrointestinal absorption (e.g., hypnotics, analgesics). Pharmacologic response to concomitantly administered oral medications should be monitored more closely following initiation, dose adjustment, or discontinuation of a GLP-1 receptor agonist or a dual GLP-1 and GIP receptor agonist.

MONITOR: Smoking cessation may lead to elevated plasma concentrations and enhanced pharmacologic effects of drugs that are substrates of CYP450 1A2 (and possibly CYP450 1A1) and/or certain drugs with a narrow therapeutic index (e.g., flecainide, pentazocine). One proposed mechanism is related to the loss of CYP450 1A2 and 1A1 induction by polycyclic aromatic hydrocarbons in tobacco smoke; when smoking cessation agents are initiated and smoking stops, the metabolism of certain drugs may decrease leading to increased plasma concentrations. The mechanism by which smoking cessation affects narrow therapeutic index drugs that are not known substrates of CYP450 1A2 or 1A1 is unknown. The clinical significance of this interaction is unknown as clinical data are lacking.

MANAGEMENT: Until more information is available, caution is advisable if smoking cessation agents are used concomitantly with drugs that are substrates of CYP450 1A2 or 1A1 and/or those with a narrow therapeutic range. Patients receiving smoking cessation agents may require periodic dose adjustments and closer clinical and laboratory monitoring of medications that are substrates of CYP450 1A2 or 1A1.

The effect of grapefruit juice on the pharmacologic activity of caffeine is controversial. One report suggests that grapefruit juice increases the effect of caffeine. The proposed mechanism is inhibition of cytochrome P-450 metabolism of caffeine. However, a well-conducted pharmacokinetic/pharmacodynamic study did not demonstrate this effect. The clinical significance of this potential interaction is unknown.