Omeprazole, amoxicillin, and rifabutin

Components of TALICIA have the potential for clinically important drug interactions. See Full Prescribing Information for important drug interactions with TALICIA. ( 4 , 5.7 )

7.1 Interactions with Other Drugs and Diagnostics Drug interaction studies with TALICIA have not been conducted. The drug interaction information described here is based on the prescribing information of individual TALICIA components: omeprazole, amoxicillin, and rifabutin. Rifabutin is a substrate and inducer of cytochrome P450 (CYP) 3A enzymes. Omeprazole is a substrate and an inhibitor of CYP2C19, and a substrate of CYP3A4. Co-administration of TALICIA and other drugs that are substrates, inhibitors, or inducers of these enzymes may alter concentrations of rifabutin/omeprazole or other co-administered drugs [See Table 2 below and Clinical Pharmacology (12.3) ].

Omeprazole magnesium is a PPI. Refer to the prescribing information of the drugs used concomitantly with TALICIA for further information on their interactions with PPIs. Table 2: Interactions with TALICIA When Co-Administered with Other Drugs and Diagnostics CYP2C19 or CYP3A4 Inducers Clinical Impact Decreased exposure of omeprazole when used concomitantly with strong inducers. Prevention or Management St. John’s Wort, rifampin : Avoid concomitant use with TALICIA [see Warnings and Precautions (5.7) ]. Ritonavir-containing products : See prescribing information for specific drugs. CYP2C19 or CYP3A4 Inhibitors Clinical Impact Increased blood levels of omeprazole and rifabutin.

Prevention or Management Voriconazole : Concomitant use with TALICIA is contraindicated [see Contraindications (4) ] . Fluconazole, posaconazole and itraconazole : Avoid concomitant use with TALICIA. If coadministration cannot be avoided, monitor patients for rifabutin associated adverse events, and lack of anti-fungal efficacy. CYP2C19 Substrates (e.g., Clopidogrel, citalopram, cilostazol, phenytoin, diazepam) Clinical Impact Increased plasma concentrations of CYP2C19 substrate drugs or decreased/increased plasma concentrations of its active metabolite(s) [see Clinical Pharmacology (12.3) ] .

Prevention or Management Clopidogrel : Consider use of alternative anti-platelet therapy [ see Warnings and Precautions (5.7) ] . Avoid concomitant use with TALICIA. Antiretrovirals/Protease Inhibitors Clinical Impact Antiretrovirals/protease inhibitors may increase rifabutin blood levels. The effect of PPIs (such as omeprazole in TALICIA) on antiretroviral drugs is variable. The clinical importance and the mechanisms behind these interactions are not always known.

Decreased exposure of some antiretroviral drugs (e.g., rilpivirine, atazanavir, and nelfinavir) when used concomitantly with omeprazole may reduce antiviral effect and promote the development of drug resistance [see Clinical Pharmacology (12.3) ]. Increased exposure of other antiretroviral drugs (e.g., saquinavir) when used concomitantly with omeprazole may increase toxicity [see Clinical Pharmacology (12.3) ] . There are other antiretroviral drugs which do not result in clinically relevant interactions with omeprazole. Prevention or Management Delavirdine : Combination treatment with TALICIA and delavirdine is contraindicated [see Contraindications (4) ].

Rilpivirine-containing products : Concomitant use with TALICIA is contraindicated [see Contraindications (4) ]. Avoid concomitant use of TALICIA with amprenavir, indinavir, lopinavir/ritonavir, saquinavir/ritonavir, ritonavir, tipranavir/ritonavir, fosamprenavir/ritonavir, or nelfinavir [see Warnings and Precautions (5.7) ] . Other antiretrovirals: See prescribing information for specific antiretroviral drugs. Probenecid Clinical Impact Increased and prolonged blood levels of amoxicillin. Allopurinol Clinical Impact Increase in the incidence of rashes is reported in patients receiving both allopurinol and amoxicillin together compared to patients receiving amoxicillin alone.

It is not known whether this potentiation of amoxicillin rashes is due to allopurinol or the hyperuricemia present in these patients. Prevention or Management Discontinue allopurinol at the first appearance of skin rash. Assess benefit-risk of continuing TALICIA treatment. Warfarin, and Other Oral Anticoagulants Clinical Impact Abnormal prolongation of prothrombin time (increased international normalized ratio [INR]) has been reported in patients receiving amoxicillin and oral anticoagulants and in patients receiving PPIs, including omeprazole, and warfarin concomitantly. Increases in INR and prothrombin time may lead to abnormal bleeding and even death.

Prevention or Management Monitor INR and prothrombin time and adjust the dose of warfarin or other oral anticoagulants to maintain the desired level of anticoagulation. Methotrexate Clinical Impact Concomitant use of omeprazole with methotrexate (primarily at high doses) may elevate and prolong serum levels of methotrexate and/or its metabolite hydroxymethotrexate, possibly leading to methotrexate toxicities [see Warnings and Precautions (5.7) ] . Prevention or Management Avoid concomitant use of TALICIA in patients receiving high-dose methotrexate. Digoxin Clinical Impact Potential for increased digoxin blood levels [see Clinical Pharmacology (12.3) ] .

Prevention or Management Monitor digoxin concentrations. Dose adjustment may be needed to maintain therapeutic drug concentrations. See digoxin prescribing information. Drugs Dependent on Gastric pH for Absorption (e.g., iron salts, erlotinib, dasatinib, nilotinib, mycophenolate mofetil, ketoconazole/itraconazole) Clinical Impact Omeprazole can alter the absorption of other drugs due to its effect of reducing intragastric acidity thereby increasing gastric pH. Prevention or Management Mycophenolate mofetil (MMF) : Use TALICIA with caution in transplant patients receiving MMF [see Clinical Pharmacology (12.3) ] .

See the prescribing information of other drugs dependent on gastric pH for absorption. Tacrolimus Clinical Impact Potential for increased tacrolimus blood levels, especially in patients who are intermediate or poor metabolizers of CYP2C19. Prevention or Management Monitor tacrolimus whole blood levels and adjust dose as per the prescribing information for tacrolimus. Drugs Metabolized via the CYP450 Enzymes (e.g., cyclosporine, disulfiram) Clinical Impact Interactions are reported with omeprazole and other drugs metabolized via the CYP450 enzymes.

Prevention or Management Monitor patients to determine if it is necessary to adjust the dosage of these other drugs when taken concomitantly with TALICIA. Oral Contraceptives Clinical Impact Concomitant use of amoxicillin and rifabutin with hormonal contraceptives may lead to loss of its efficacy due to lower estrogen reabsorption and decreased ethinylestradiol and norethindrone concentrations, respectively [see Warnings and Precautions (5.5) ] . Prevention or Management Patients should be advised to use additional or alternative non-hormonal methods of contraception.

Diagnostic Investigations for Neuroendocrine Tumors Clinical Impact PPI-induced decrease in gastric acidity may lead to increased serum chromogranin A (CgA) levels, which may cause false positive results in diagnostics for neuroendocrine tumors [see Warnings and Precautions (5.11) ] . Prevention or Management Assess CgA levels at least 14 days after stopping TALICIA treatment and consider repeating the test if initial CgA levels are high. If serial tests are performed (e.g., for monitoring), the same commercial laboratory should be used for testing, as reference ranges between tests may vary.

Urine Glucose Test Clinical Impact High urine concentrations of ampicillin or amoxicillin may result in false-positive reactions when using glucose tests based on the Benedict’s copper reduction reaction that determines the amount of reducing substances like glucose in the urine. Prevention or Management Glucose tests based on enzymatic glucose oxidase reactions should be used. Interaction with Secretin Stimulation Test Clinical Impact Hyper-response in gastrin secretion in response to secretin stimulation test may falsely suggest gastrinoma. Prevention or Management Test should be performed at least 14 days after stopping TALICIA treatment to allow gastrin levels to return to baseline.

False Positive Urine Tests for Tetrahydrocannabinol (THC) Clinical Impact There have been reports of false positive urine screening tests for THC in patients receiving PPIs. Prevention or Management An alternative confirmatory method should be considered to verify positive results. Other Laboratory Tests Clinical Impact Following administration of ampicillin or amoxicillin to pregnant women, a transient decrease in plasma concentration of total conjugated estriol, estriol-glucuronide, conjugated estrone, and estradiol has been noted.

8.1 Pregnancy Risk Summary Based on animal reproduction studies, TALICIA may cause fetal harm when administered to pregnant women. There are no adequate and well controlled studies of amoxicillin, omeprazole, or rifabutin (used separately or together) in pregnant women. Use of TALICIA is generally not recommended for use in pregnancy. If TALICIA is used during pregnancy, advise pregnant women of the potential risk to a fetus. Omeprazole: Available epidemiologic data do not demonstrate an increased risk of major congenital malformations or other adverse pregnancy outcomes with first trimester omeprazole use.

Reproduction studies in rats and rabbits resulted in dose-dependent embryo-lethality at omeprazole doses that were approximately 1.13 to 11 times an oral human dose of 120 mg. Fetal malformations were not observed in animal reproduction studies with administration of oral esomeprazole (an enantiomer of omeprazole) magnesium in rats and rabbits during organogenesis with doses about 23 times and 14 times, respectively, of an oral human dose of 120 mg esomeprazole or omeprazole.

Changes in bone morphology were observed in offspring of rats dosed through most of pregnancy and lactation at doses equal to or greater than approximately 11 times an oral human dose of 120 mg esomeprazole or omeprazole. When maternal administration was confined to gestation only, there were no effects on bone physeal morphology in the offspring at any age [see Data ] . Amoxicillin: Available data from published epidemiologic studies and pharmacovigilance case reports over several decades with amoxicillin use have not established drug-associated risks of major birth defects, miscarriage, or adverse maternal or fetal outcomes [see Data ] .

No adverse developmental effects were observed in animal reproduction studies with administration of amoxicillin to pregnant mice and at doses up to 3 to 6 times an oral human dose of 3 grams. Rifabutin: Fetal malformations were not observed in rat or rabbit reproduction studies given rifabutin at dose levels up to 200 mg/kg (6 to 13 times the recommended human dose). In rats, given rifabutin at 200 mg/kg/day (about 6 times the recommended human daily dose), there was a decrease in fetal viability.

Increased skeletal anomalies were observed in rats and rabbits at 40 and 80 mg/kg/day, respectively (corresponding to approximately an equivalent dose and 5 times the recommended human daily dose); maternal toxicity was noted at 80 mg/kg in rabbits [see Data ]. The estimated background risks of major birth defects and miscarriage for the indicated…