Drug Interactions between simvastatin and Tylox

GENERALLY AVOID: Alcohol may potentiate the central nervous system (CNS) depressant effects of opioid analgesics including oxycodone. Concomitant use may result in additive CNS depression and impairment of judgment, thinking, and psychomotor skills. In more severe cases, hypotension, respiratory depression, profound sedation, coma, or even death may occur.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of oxycodone. The proposed mechanism is inhibition of CYP450 3A4-mediated metabolism of oxycodone by certain compounds present in grapefruit, resulting in decreased formation of metabolites noroxycodone and noroxymorphone and increased formation of oxymorphone due to a presumed shifting of oxycodone metabolism towards the CYP450 2D6-mediated route. In 12 healthy, nonsmoking volunteers, administration of a single 10 mg oral dose of oxycodone hydrochloride on day 4 of a grapefruit juice treatment phase (200 mL three times a day for 5 days) increased mean oxycodone peak plasma concentration (Cmax), systemic exposure (AUC) and half-life by 48%, 67% and 17% (from 3.5 to 4.1 hours), respectively, compared to administration during an equivalent water treatment phase. Grapefruit juice also decreased the metabolite-to-parent AUC ratio of noroxycodone by 44% and that of noroxymorphone by 45%. In addition, oxymorphone Cmax and AUC increased by 32% and 56%, but the metabolite-to-parent AUC ratio remained unchanged. Pharmacodynamic changes were modest and only self-reported performance was significantly impaired after grapefruit juice. Analgesic effects were not affected.

MANAGEMENT: Patients should not consume alcoholic beverages or use drug products that contain alcohol during treatment with oxycodone. Any history of alcohol or illicit drug use should be considered when prescribing oxycodone, and therapy initiated at a lower dosage if necessary. Patients should be closely monitored for signs and symptoms of sedation, respiratory depression, and hypotension. Due to a high degree of interpatient variability with respect to grapefruit juice interactions, patients treated with oxycodone may also want to avoid or limit the consumption of grapefruit and grapefruit juice.

GENERALLY AVOID: Coadministration with grapefruit juice may significantly increase the plasma concentrations of lovastatin and simvastatin and their active acid metabolites. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. When a single 60 mg dose of simvastatin was coadministered with 200 mL of double-strength grapefruit juice three times a day, simvastatin systemic exposure (AUC) increased by 16-fold and simvastatin acid AUC increased by 7-fold. Administration of a single 20 mg dose of simvastatin with 8 ounces of single-strength grapefruit juice increased the AUC of simvastatin and simvastatin acid by 1.9-fold and 1.3-fold, respectively. The interaction has also been reported with lovastatin, which has a similar metabolic profile to simvastatin. Clinically, high levels of HMG-CoA reductase inhibitory activity in plasma is associated with an increased risk of musculoskeletal toxicity. Myopathy manifested as muscle pain and/or weakness associated with grossly elevated creatine kinase exceeding ten times the upper limit of normal has been reported occasionally. Rhabdomyolysis has also occurred rarely, which may be accompanied by acute renal failure secondary to myoglobinuria and may result in death.

ADJUST DOSING INTERVAL: Fibres such as oat bran and pectin may diminish the pharmacologic effects of HMG-CoA reductase inhibitors by interfering with their absorption from the gastrointestinal tract.

Coadministration with green tea may increase the plasma concentrations of simvastatin. The mechanism of interaction has not been established, but may involve inhibition of organic anion transporting polypeptide (OATP) 1B1- and/or 2B1-mediated hepatic uptake of simvastatin by catechins in green tea. The interaction was suspected in a 61-year-old man who experienced muscle intolerance during treatment with simvastatin while drinking an average of 3 cups of green tea daily. He also experienced similar muscle intolerance (leg cramps without creatine phosphokinase elevation) during treatments with atorvastatin and rosuvastatin while drinking green tea. Pharmacokinetic studies performed during his usual green tea intake demonstrated an approximately two-fold higher exposure to simvastatin lactone (the administered form of simvastatin) than that observed after stopping green tea intake for a month. He was also able to tolerate simvastatin after discontinuing green tea consumption. The authors of the report subsequently conducted two independent studies to assess the effect of different green tea preparations on simvastatin pharmacokinetics. One study was conducted in 12 Italian subjects and the other in 12 Japanese subjects. In the Italian study, administration of a single 20 mg dose of simvastatin following pretreatment with 200 mL of a hot green tea standardized infusion 3 times daily for 14 days (estimated daily intake of 335 mg total catechins and 173 mg epigallocatechin-3-gallate (EGCG), the most abundant and biologically active catechin in green tea) was found to have no significant effect on mean peak plasma concentration (Cmax) or systemic exposure (AUC) of simvastatin lactone and simvastatin acid relative to administration with water. However, green tea increased simvastatin lactone AUC (0-6h) by about two-fold in 3 of the study subjects. In the Japanese study, administration of a single 10 mg dose of simvastatin following pretreatment with 350 mL of a commercial green tea beverage twice daily for 14 days (estimated daily intake of 638 mg total catechins and 322 mg EGCG) did not affect mean simvastatin lactone Cmax or AUC to a statistically significant extent compared to administration with water, but increased mean simvastatin acid Cmax and AUC by 42% and 22%, respectively. Similar to the first study, green tea increased simvastatin lactone AUC (0-6h) by two- to three-fold in 4 of the study subjects. Although not studied, the interaction may also occur with lovastatin due to its similar metabolic profile to simvastatin.

MANAGEMENT: Patients receiving therapy with lovastatin, simvastatin, or red yeast rice (which contains lovastatin) should be advised to avoid the consumption of grapefruit and grapefruit juice. Fluvastatin, pravastatin, pitavastatin, and rosuvastatin are metabolized by other enzymes and may be preferable alternatives in some individuals. All patients receiving statin therapy should be advised to promptly report any unexplained muscle pain, tenderness or weakness, particularly if accompanied by fever, malaise and/or dark colored urine. Therapy should be discontinued if creatine kinase is markedly elevated in the absence of strenuous exercise or if myopathy is otherwise suspected or diagnosed. Also, patients should either refrain from the use of oat bran and pectin, or separate the administration times by at least 2 to 4 hours if concurrent use cannot be avoided. Caution may be advisable when coadministered with green tea or green tea extracts. Dosing reduction of the statin and/or limiting consumption of green tea and green tea products may be required if an interaction is suspected.

GENERALLY AVOID: Chronic, excessive consumption of alcohol may increase the risk of acetaminophen-induced hepatotoxicity, which has included rare cases of fatal hepatitis and frank hepatic failure requiring liver transplantation. The proposed mechanism is induction of hepatic microsomal enzymes during chronic alcohol use, which may result in accelerated metabolism of acetaminophen and increased production of potentially hepatotoxic metabolites.

MANAGEMENT: In general, chronic alcoholics should avoid regular or excessive use of acetaminophen. Alternative analgesic/antipyretic therapy may be appropriate in patients who consume three or more alcoholic drinks per day. However, if acetaminophen is used, these patients should be cautioned not to exceed the recommended dosage (maximum 4 g/day in adults and children 12 years of age or older).

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.

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.