Drug Interactions between Fanatrex and Tussigon

MONITOR CLOSELY: Concomitant use of opioids with gabapentinoids (e.g., gabapentin, pregabalin) may increase the risk of opioid overdose and serious adverse effects such as profound sedation, respiratory depression, syncope, and death due to potentially additive depressant effects on the central nervous system. Using administrative databases, investigators (Gomes T, et al.) conducted a matched case-control study among residents of Ontario, Canada, who received opioid analgesics for non-cancer pain (n=5875; 1256 cases who died of an opioid-related cause and 4619 matched controls) and found that concomitant gabapentin exposure was associated with a 49% higher risk of death from an opioid overdose after adjustment for potential confounders including opioid dose. Moreover, moderate-dose (900 to 1799 mg daily) and high-dose (>=1800 mg daily) gabapentin use was associated with a nearly 60% increase in the odds of opioid-related death compared to no concomitant gabapentin use, and very high-dose (>=2500 mg daily) gabapentin use was associated with a nearly 2-fold increase. By contrast, no significant association between concomitant exposure to nonsteroidal anti-inflammatory drugs (NSAIDs) and opioid-related death was observed in a prespecified sensitivity analysis. Concomitant use of opioids has also been reported to increase the risk of gabapentinoid misuse or abuse, particularly in patients with a history of addiction. One retrospective cohort analysis of claims data for a commercially insured U.S. population found that among patients with prolonged gabapentin use (>=120 days over a one year period), concomitant prolonged treatment with opioids increased the risk of misuse of one or both drugs by more than 6-fold. Data from several small studies suggest that in the United States and Europe, approximately 15% to 26% and 7% to 21% of patients with opioid use disorder also misused or abused gabapentin and pregabalin, respectively. Concurrent overuse of both opioids and gabapentin has been reported to quadruple the odds of an emergency department visit or hospital stay for respiratory depression.

Coadministration with opioids may increase the oral bioavailability of gabapentin. The precise mechanism has not been established, but may involve increased gabapentin absorption due to delayed gastrointestinal transit induced by opioids. In 12 healthy male volunteers, single-dose administration of gabapentin 600 mg two hours following controlled-release morphine sulfate 60 mg increased gabapentin systemic exposure (AUC) by 44% and decreased apparent oral clearance and apparent renal clearance by 23% and 16%, respectively, compared to administration with placebo. The pharmacokinetics of morphine and its glucuronides were not altered. Gabapentin has also been reported to reduce the plasma concentrations of hydrocodone in a dose-dependent manner. The mechanism of this interaction is unknown. When immediate-release gabapentin 125 mg or 500 mg was coadministered with hydrocodone 10 mg, hydrocodone Cmax decreased by 3% and 21%, respectively, while AUC decreased by 4% and 22%, respectively. Gabapentin AUC was increased 14% by hydrocodone.

MANAGEMENT: Caution is advised when opioids and gabapentinoids are coadministered, particularly in patients with additional risk factors for respiratory depression such as advanced age, renal insufficiency, or chronic lung disease. The dosage and duration of each drug should be limited to the minimum required to achieve desired clinical effect, with cautious titration and dosage adjustments when needed. Use of additional central nervous system depressants should be avoided if possible. Patients should be monitored closely for signs and symptoms of respiratory depression and sedation, and advised to avoid driving or operating hazardous machinery until they know how these medications affect them. For patients who have been receiving extended therapy with both an opioid and a gabapentinoid (either for analgesia or seizure control) and require discontinuation of either medication, a gradual tapering of dose is advised, since abrupt withdrawal may lead to withdrawal symptoms and increased seizure risk.

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MONITOR: Coadministration of opioids with anticholinergic agents may result in additive central nervous system (CNS), gastrointestinal, and genitourinary effects. The risk and/or severity of adverse effects such as sedation, dizziness, confusion, cognitive and psychomotor impairment, dry mouth, constipation, and urinary retention may increase. Severe constipation may lead to paralytic ileus in some cases.

MANAGEMENT: Caution and close monitoring of central nervous system, gastrointestinal, and genitourinary adverse effects are recommended when opioids are used with anticholinergic agents. Ambulatory patients should be counseled to avoid hazardous activities requiring mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.

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