Drug Interactions between isoniazid / rifampin and lixisenatide

GENERALLY AVOID: Concurrent use of rifampin in patients who ingest alcohol daily may result in an increased incidence of hepatotoxicity. The increase in hepatotoxicity may be due to an additive risk as both alcohol and rifampin are individually associated with this adverse reaction. However, the exact mechanism has not been established.

ADJUST DOSING INTERVAL: Administration with food may reduce oral rifampin absorption, increasing the risk of therapeutic failure or resistance. In a randomized, four-period crossover phase I study of 14 healthy male and female volunteers, the pharmacokinetics of single dose rifampin 600 mg were evaluated under fasting conditions and with a high-fat meal. Researchers observed that administration of rifampin with a high-fat meal reduced rifampin peak plasma concentration (Cmax) by 36%, nearly doubled the time to reach peak plasma concentration (Tmax) but reduced overall exposure (AUC) by only 6%.

MANAGEMENT: The manufacturer of oral forms of rifampin recommends administration on an empty stomach, 30 minutes before or 2 hours after meals. Patients should be encouraged to avoid alcohol or strictly limit their intake. Patients who use alcohol and rifampin concurrently or have a history of alcohol use disorder may require additional monitoring of their liver function during treatment with rifampin.

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GENERALLY AVOID: Concurrent use of isoniazid (INH) in patients who ingest alcohol daily may result in an increased incidence of both hepatotoxicity and peripheral neuropathy. The increase in hepatotoxicity may be due to an additive risk as both alcohol and INH are individually associated with this adverse reaction. INH-associated hepatotoxicity is believed to be due to an accumulation of toxic metabolites and may also be partly immune mediated, though the exact mechanisms are not universally agreed upon. INH is metabolized by N-acetyltransferase and CYP450 2E1. The rate of acetylation is genetically determined and generally classified as slow or rapid. Slow acetylators have been identified by some studies as having a higher risk of hepatotoxicity; therefore, this interaction may be more significant for patients who fall into this category. Other studies have postulated that alcohol-mediated CYP450 2E1 induction may play a role, as this isoenzyme is involved in INH metabolism and may be responsible for producing hepatotoxic metabolites. However, available literature is conflicting. The labeling for some INH products lists daily alcohol use or chronic alcoholism as a risk factor for hepatitis, but not all studies have found a significant association between alcohol use and INH-induced hepatotoxicity. Additionally, INH and alcohol are both associated with pyridoxine (B6) deficiency, which may increase the risk of peripheral neuropathy.

GENERALLY AVOID: Concomitant administration of isoniazid (INH) with foods containing tyramine and/or histamine may increase the risk of symptoms relating to tyramine- and/or histamine toxicity (e.g., headache, diaphoresis, flushing, palpitations, and hypotension). The proposed mechanism is INH-mediated inhibition of monoamine oxidase (MAO) and diamine oxidase (DAO), enzymes responsible for the metabolism of tyramine and histamine, respectively. Some authors have suggested that the reactions observed are mainly due to INH's effects on DAO instead of MAO or the amounts of histamine instead of tyramine present in the food. A Japanese case report recorded an example in 8 out of 25 patients on the tuberculosis ward who developed an accidental histamine poisoning after ingesting a fish paste (saury). Patients developed allergy-like symptoms, which started between 20 minutes and 2 hours after ingesting the food. A high-level of histamine (32 mg/100 g of fish) was confirmed in the saury paste and all 8 patients were both on INH and had reduced MAO concentrations. The 17 remaining patients were not on INH (n=5) or reported not eating the saury paste (n=12).

ADJUST DOSING INTERVAL: Administration with food significantly reduces oral isoniazid (INH) absorption, increasing the risk of therapeutic failure or resistance. The mechanism is unknown. Pharmacokinetic studies completed in both healthy volunteers (n=14) and tuberculosis patients (n=20 treatment-naive patients during days 1 to 3 of treatment) have resulted in almost doubling the time to reach INH's maximum concentration (tmax) and a reduction in isoniazid's maximum concentration (Cmax) of 42%-51% in patients who consumed high-fat or high-carbohydrate meals prior to INH treatment.

MANAGEMENT: The manufacturer of oral forms of isoniazid (INH) recommends administration on an empty stomach (i.e., 30 minutes before or 2 hours after meals). Patients should be encouraged to avoid alcohol or strictly limit their intake. Patients who use alcohol and INH concurrently or have a history of alcohol use disorder may require additional monitoring of their liver function during treatment with INH. Concomitant pyridoxine (B6) administration is also recommended to reduce the risk of peripheral neuropathy, with some authorities suggesting a dose of at least 10 mg/day. Patients should be advised to avoid foods containing tyramine (e.g., aged cheese, cured meats such as sausages and salami, fava beans, sauerkraut, soy sauce, beer, or red wine) or histamine (e.g., skipjack, tuna, mackerel, salmon) during treatment with isoniazid. Consultation of product labeling for combination products containing isoniazid and/or relevant guidelines may be helpful for more specific recommendations.

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ADJUST DOSING INTERVAL: Lixisenatide slows gastric emptying, which may impact the absorption of concomitantly administered oral medications. The interaction has been studied with various medications, which demonstrated primarily an effect on the rate rather than the overall extent of absorption.

Acetaminophen: When acetaminophen 1000 mg was administered 1 hour and 4 hours after lixisenatide 10 mcg injection, acetaminophen peak plasma concentration (Cmax) was decreased by 29% and 31%, respectively; and median time to peak plasma concentration (Tmax) was delayed by 2 hours and 1.75 hours, respectively. The Cmax and Tmax of acetaminophen were not significantly altered when acetaminophen was given one hour before lixisenatide injection, and systemic exposure (AUC) was not affected whether administered before or after lixisenatide administration. Based on these results, no dose adjustment for acetaminophen is required; however, it may be advisable to take acetaminophen at least one hour before lixisenatide if a rapid onset of action is required.

Oral Contraceptives: When an oral contraceptive containing ethinyl estradiol 0.03 mg and levonorgestrel 0.15 mg was administered 1 hour and 4 hours after lixisenatide 10 mcg injection, ethinyl estradiol Cmax was decreased by 52% and 39%, respectively, while levonorgestrel Cmax was decreased by 46% and 20%, respectively. Median Tmax values were delayed by 1 to 3 hours, but overall exposure (AUC) and mean terminal half-life (T1/2) of ethinyl estradiol and levonorgestrel were not significantly altered. Administration of the oral contraceptive 1 hour before or 11 hours after lixisenatide had no effect on any of the measured pharmacokinetic parameters of either ethinyl estradiol or levonorgestrel. Based on these results, no dose adjustment for oral contraceptives is required; however, some authorities recommend that oral contraceptives be administered at least 1 hour before or 11 hours after lixisenatide.

Atorvastatin: When atorvastatin 40 mg and lixisenatide 20 mcg were coadministered in the morning for 6 days, atorvastatin Cmax was decreased by 31% and Tmax was delayed by 3.25 hours, but AUC was not affected. When atorvastatin was administered in the evening and lixisenatide in the morning, the AUC and Cmax of atorvastatin were increased by 27% and 66%, respectively, but there was no change in Tmax. Based on these results, no dose adjustment for atorvastatin is required; however, some authorities recommend that atorvastatin be administered at least 1 hour before lixisenatide.

Warfarin: When warfarin 25 mg was coadministered with repeated dosing of lixisenatide 20 mcg, warfarin Cmax was decreased by 19% and Tmax was delayed by 7 hours, but there were no effects on AUC or International Normalized Ratio (INR). Based on these results, no dose adjustment for warfarin is required; however, closer monitoring of INR may be appropriate following initiation or discontinuation of lixisenatide treatment.

Digoxin: When digoxin 0.25 mg and lixisenatide 20 mcg were coadministered at steady state, digoxin Cmax was decreased by 26% and Tmax was delayed by 1.5 hours, but AUC was not affected. Based on these results, no dose adjustment for digoxin is required.

Ramipril: When ramipril 5 mg and lixisenatide 20 mcg were coadministered for 6 days, ramipril Cmax was decreased by 63% and AUC was increased by 21%, while Cmax and AUC of the active metabolite (ramiprilat) were not affected. The Tmax values of ramipril and ramiprilat were delayed by approximately 2.5 hours. Based on these results, no dose adjustment for ramipril is required.

MANAGEMENT: Caution is advised during concomitant use of lixisenatide with oral medications that have a narrow therapeutic index or that require careful clinical monitoring. These medications should be administered on a consistent schedule relative to lixisenatide, and blood levels and/or pharmacologic effects should be closely monitored. In addition, if they are to be administered with food, patients should be advised to take them with a meal or snack when lixisenatide is not administered. Oral medications that are particularly dependent on threshold concentrations for efficacy, such as antibiotics, or medications for which a delay in effect is undesirable, such as acetaminophen, should be administered at least 1 hour before lixisenatide. Gastro-resistant formulations containing substances sensitive to stomach degradation should be administered 1 hour before or 4 hours after lixisenatide. Patients taking oral contraceptives should be advised to take them at least 1 hour before or 11 hours after lixisenatide.

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