Drug Interaction Report

MONITOR: Coadministration of the radiopharmaceutical technetium (Tc99m) mertiatide with another drug that is also eliminated by active tubular secretion may result in increased plasma concentrations of one or both drugs. The exact mechanism has not been fully described but may involve competition in binding to organic anion transporter 1 (OAT1) in the proximal tubule of the kidney, which is involved in moving some drugs from the blood into the urine. The risk and significance of this interaction may vary. Some sources state that the risk is expected with diuretics like hydrochlorothiazide, but only theoretical with others (e.g., nonsteroidal anti-inflammatory drugs). Delayed excretion of Tc99m mertiatide may affect the efficacy of the diagnostic procedure. However, clinical data are limited. One crossover study conducted in 12 healthy male volunteers (22-25 years old), reviewed the differences in scans using Tc99m mertiatide injection alone to those obtained when subjects received either a selective OAT1 substrate (10% sodium p-aminohippurate (PAH) given via intravenous infusion at 120 mg/min 10 minutes prior to and during the scan) or a potent OAT1 inhibitor (probenecid 750 mg 1 hour prior to the scan). PAH appeared to have a greater impact than probenecid, increasing the late phase (30-60 minutes post radiopharmaceutical injection) plasma clearance half-life of Tc99m mertiatide from approximately 27.7 minutes to 54.9 minutes. However, in some circumstances, the administration of an NSAID or other medication that affects the secretion of Tc99m mertiatide may be clinically indicated. For example, there are some protocols that utilize aspirin to enhance Tc99m mertiatide renography for the investigation/diagnosis of renal artery stenosis.

MANAGEMENT: Caution is recommended with the concomitant administration of technetium (Tc99m) mertiatide with drugs that are secreted in the proximal tubule due to the potential to affect the efficacy of the diagnostic procedure. Likewise, since Tc99m mertiatide may also delay the excretion of other drugs eliminated via this route, monitoring for excessive pharmacologic effects of both drugs should be considered. Current clinical guidelines and/or manufacturer's labeling should be consulted for more specific information and guidance. Dehydration and acidosis can also impact kidney function and prolong renal drug elimination. Refer to the product labeling or local protocols for guidelines on patient hydration prior to testing with Tc99m mertiatide.

GENERALLY AVOID: The concurrent use of aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) and ethanol may lead to gastrointestinal (GI) blood loss. The mechanism may be due to a combined local effect as well as inhibition of prostaglandins leading to decreased integrity of the GI lining.

MANAGEMENT: Patients should be counseled on this potential interaction and advised to refrain from alcohol consumption while taking aspirin or NSAIDs.

MONITOR: Concomitant use of statin medication with substantial quantities of alcohol may increase the risk of hepatic injury. Transient increases in serum transaminases have been reported with statin use and while these increases generally resolve or improve with continued therapy or a brief interruption in therapy, there have been rare postmarketing reports of fatal and non-fatal hepatic failure in patients taking statins. Patients who consume substantial quantities of alcohol and/or have a history of liver disease may be at increased risk for hepatic injury. Active liver disease or unexplained transaminase elevations are contraindications to statin use.

MANAGEMENT: Patients should be counseled to avoid substantial quantities of alcohol in combination with statin medications and clinicians should be aware of the increased risk for hepatotoxicity in these patients.

One study has reported that coadministration of caffeine and aspirin lead to a 25% increase in the rate of appearance and 17% increase in maximum concentration of salicylate in the plasma. A significantly higher area under the plasma concentration time curve of salicylate was also reported when both drugs were administered together. The exact mechanism of this interaction has not been specified. Physicians and patients should be aware that coadministration of aspirin and caffeine may lead to higher salicylate levels faster.