Drug Interactions between bismuth subcitrate potassium and lidocaine / oxytetracycline

Grapefruit juice may increase the blood levels of lidocaine, which may increase the risk of side effects such as low blood pressure, slow heart rate, irregular heart rhythm, difficulty breathing and convulsions. Cigarette smoking may reduce the blood levels of lidocaine, which may make the medication less effective. It is best to avoid smoking during lidocaine therapy. Consuming cruciferous vegetables (e.G., broccoli, brussels sprouts) may also reduce the blood levels of lidocaine. Talk to a healthcare professional if you have any questions or concerns. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Do not take iron supplements, multivitamins, calcium supplements, antacids, or laxatives within 2 hours before or after taking oxytetracycline. These products can make oxytetracycline less effective in treating your infection. Do not take oxytetracycline with milk or other dairy products, unless your doctor has told you to. Dairy products can make it harder for your body to absorb the medication.

Consumer information for this interaction is not currently available.

ADJUST DOSING INTERVAL: Food may impair the gastrointestinal absorption and decrease the bioavailability of bismuth from the administration of bismuth subcitrate potassium (also known as colloidal bismuth subcitrate or tripotassium dicitratobismuthate). The clinical significance of this effect is unknown, as the relative importance of systemic versus local bismuth concentrations for antimicrobial activity against Helicobacter pylori has not been established. Investigators have suggested that the increased gastric retention time of bismuth in the presence of food may be beneficial by prolonging the local exposure of Helicobacter pylori to high concentrations of bismuth, although the amount of bismuth absorbed systemically and secreted back into the gastric fluid may also contribute to its therapeutic effect. When Pylera (a treatment preparation for Helicobacter pylori infection that contains bismuth subcitrate potassium 420 mg, metronidazole 375 mg, and tetracycline 375 mg per recommended dose) was administered after a standardized high-fat breakfast in 23 healthy volunteers, mean systemic exposure (AUC) for bismuth decreased by 60% compared to administration in the fasting state. Metronidazole and tetracycline AUC values were also reduced by 6% and 34%, respectively. However, these changes are not deemed clinically relevant, as eradication rates of Helicobacter pylori near 90% have been reported in trial patients administered Pylera routinely after meals.

MANAGEMENT: Pylera and generic equivalents should be administered after meals (breakfast, lunch, and dinner) and at bedtime (preferably with a snack). The manufacturers for some of the other bismuth subcitrate potassium products have recommended avoiding the ingestion of food, beverages, or other medications within one-half hour before and after each dose. The prescribing information or package labeling should be consulted for dosing and administration instructions that are appropriate for each product.

Iron can bind to oxytetracycline in the gastrointestinal tract, which may prevent their absorption into the bloodstream and possibly reduce their effectiveness. To avoid or minimize the interaction, iron-containing medications and oxytetracycline should preferably be taken at least three to four hours apart in most cases. Talk to your doctor if you have any questions or concerns, or if you have trouble separating the dosing times. Your doctor may be able to prescribe alternatives that do not interact. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

Consumer information for this interaction is not currently available.

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.