Drug Interactions between amoxicillin / clarithromycin / omeprazole and pasireotide

MONITOR CLOSELY: Pasireotide can cause bradycardia and QT prolongation. Theoretically, coadministration with other agents that can prolong the QT interval may result in additive effects and increased risk of ventricular arrhythmias including torsade de pointes and sudden death. In healthy study subjects given therapeutic (0.6 mg twice daily) and supratherapeutic (1.95 mg twice daily) dosages of pasireotide, the maximum mean placebo-subtracted QTcI change from baseline was 12.7 msec and 16.6 msec, respectively. Both dosages decreased heart rate, with a maximum mean placebo-subtracted change from baseline of -10.9 beats per minute (bpm) observed at 1.5 hours for the therapeutic dosage and -15.2 bpm at 0.5 hours for the supratherapeutic dosage. The mean steady-state peak plasma concentration (Cmax) produced by the supratherapeutic dosage was 3.3-fold that observed with the therapeutic dosage. In clinical studies of patients with Cushing's disease, two of 201 patients experienced single occurrences of QTcF exceeding 500 msec. Torsade des pointes arrhythmias were not observed in these or other studies. In general, the risk of an individual agent or a combination of agents causing ventricular arrhythmia in association with QT prolongation is largely unpredictable but may be increased by certain underlying risk factors such as congenital long QT syndrome, cardiac disease, and electrolyte disturbances (e.g., hypokalemia, hypomagnesemia). In addition, the extent of drug-induced QT prolongation is dependent on the particular drug(s) involved and dosage(s) of the drug(s).

MANAGEMENT: Caution is recommended if pasireotide is used in combination with other drugs that can prolong the QT interval. ECG and serum electrolytes, including potassium, magnesium and calcium, should be monitored before starting pasireotide therapy and periodically during treatment in accordance with the product labeling. Hypokalemia and hypomagnesemia must be corrected prior to pasireotide administration. Patients should be advised to seek prompt medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, lightheadedness, fainting, palpitation, irregular heart rhythm, shortness of breath, or syncope.

Although some in vitro data indicate synergism between macrolide antibiotics and penicillins, other in vitro data indicate antagonism. When these drugs are given together, neither has predictable therapeutic efficacy. Data are available for erythromycin, although theoretically this interaction could occur with any macrolide. Except for monitoring of the effectiveness of antibiotic therapy, no special precautions appear to be necessary.

Clarithromycin may increase and prolong the omeprazole plasma concentration. The mechanism may be related to clarithromycin inhibition of hepatic cytochrome P450 enzymes responsible for omeprazole metabolism. Coadministration of omeprazole may result in an increase in clarithromycin and 14-(R)-hydroxyclarithromycin plasma concentrations. These increases may be due to the effect of omeprazole on gastric pH.