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Drug Interaction Report

This report displays the potential drug interactions for the following 2 drugs:

  • verapamil
  • fentanyl

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Interactions between your drugs

Major

verapamil fentaNYL

Applies to: verapamil, fentanyl

MONITOR CLOSELY: Coadministration with inhibitors of CYP450 3A4 may increase the plasma concentrations of fentanyl, which is primarily metabolized by the isoenzyme. Increased fentanyl concentrations could increase or prolong adverse drug effects and may cause potentially fatal respiratory depression. Conversely, discontinuation of a CYP450 3A4 inhibitor could decrease fentanyl plasma concentrations, decrease opioid efficacy, and possibly even lead to a withdrawal syndrome in patients who had developed physical dependence to fentanyl. In eleven healthy volunteers, coadministration of the potent inhibitor ritonavir (200 mg orally three times a day on day 1; 300 mg three times a day on day 2; one morning dose of 300 mg on day 3) and intravenous fentanyl (5 mcg/kg two hours after the afternoon dose of ritonavir on day 2) resulted in a 174% increase in fentanyl systemic exposure (AUC) and a 67% decrease in fentanyl clearance compared to administration of fentanyl alone (with placebo). No other formulations of fentanyl such as patches or buccal tablets were studied.

MANAGEMENT: Patients receiving fentanyl with potent or moderate CYP450 3A4 inhibitors should be carefully monitored, and dosage adjustments made accordingly as needed. This is particularly important when an inhibitor is added after a stable dose of fentanyl has been achieved. Some authorities recommend avoiding concomitant use of fentanyl during and for 2 weeks after treatment with itraconazole. Patients and/or their caregivers should be advised to seek medical attention if potential signs and symptoms of toxicity occur, such as dizziness, confusion, fainting, extreme sedation, unresponsiveness, bradycardia, slow or difficult breathing, and shortness of breath. When discontinuing CYP450 3A4 inhibitors, monitor patients closely at frequent intervals and consider increasing the opioid dosage if needed to maintain adequate analgesia or if symptoms of opioid withdrawal occur. Patients treated with transdermal formulations of fentanyl should be cautioned that drug interactions and drug effects may be observed for a prolonged period beyond removal of the patch, as significant amounts of fentanyl are absorbed from the skin for 17 hours or more after the patch is removed.

References

  1. Tateishi T, Krivoruk Y, Ueng YF, Wood AJ, Guengerich FP, Wood M "Identification of human cytochrome P-450 3A4 as the enzyme responsible for fentanyl and sufentanil N-dealkylation." Anesth Analg 82 (1996): 167-72
  2. Ibrahim AE, Feldman J, Karim A, Kharasch ED "Simultaneous Assessment of Drug Interactions with Low- and High-Extraction Opioids: Application to Parecoxib Effects on the Pharmacokinetics and Pharmacodynamics of Fentanyl and Alfentanil." Anesthesiology 98 (2003): 853-861
  3. "Product Information. Duragesic Transdermal System (fentanyl)." Janssen Pharmaceutica, Titusville, NJ.
  4. Cerner Multum, Inc. "Australian Product Information." O 0
  5. "Product Information. Actiq (fentanyl)." Abbott Pharmaceutical, Abbott Park, IL.
  6. Labroo RB, Paine MF, Thummel KE, Kharasch ED "Fentanyl metabolism by human hepatic and intestinal cytochrome P450 3A4: implicaitons for interindividual variability in disposition, efficacy, and drug interactions." Drug Metab Dispos 25 (1997): 1072-80
  7. "Product Information. Sporanox (itraconazole)." Janssen Pharmaceutica, Titusville, NJ.
View all 7 references

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Drug and food interactions

Major

fentaNYL food

Applies to: fentanyl

GENERALLY AVOID: Alcohol may potentiate the central nervous system (CNS) depressant effects of opioid analgesics including fentanyl. 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: Consumption of grapefruit juice during treatment with oral transmucosal formulations of fentanyl may result in increased plasma concentrations of fentanyl, which is primarily metabolized by CYP450 3A4 isoenzyme in the liver and intestine. Certain compounds present in grapefruit are known to inhibit CYP450 3A4 and may increase the bioavailability of swallowed fentanyl (reportedly up to 75% of a dose) and/or decrease its systemic clearance. The clinical significance is unknown. In 12 healthy volunteers, consumption of 250 mL regular-strength grapefruit juice the night before and 100 mL double-strength grapefruit juice one hour before administration of oral transmucosal fentanyl citrate (600 or 800 mcg lozenge) did not significantly affect fentanyl pharmacokinetics, overall extent of fentanyl-induced miosis (miosis AUC), or subjective self-assessment of various clinical effects compared to control. However, pharmacokinetic alterations associated with interactions involving grapefruit juice are often subject to a high degree of interpatient variability. The possibility of significant interaction in some patients should be considered.

MANAGEMENT: Patients should not consume alcoholic beverages or use drug products that contain alcohol during treatment with fentanyl. Any history of alcohol or illicit drug use should be considered when prescribing fentanyl, 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 fentanyl should preferably avoid the consumption of grapefruit and grapefruit juice. In addition, patients receiving transdermal formulations of fentanyl should be cautioned that drug interactions and drug effects may be observed for a prolonged period beyond removal of the patch, as significant amounts of fentanyl are absorbed from the skin for 17 hours or more after the patch is removed.

References

  1. Kharasch ED, Whittington D, Hoffer C "Influence of Hepatic and Intestinal Cytochrome P4503A Activity on the Acute Disposition and Effects of Oral Transmucosal Fentanyl Citrate." Anesthesiology 101 (2004): 729-737
  2. "Product Information. Duragesic Transdermal System (fentanyl)." Janssen Pharmaceutica, Titusville, NJ.
  3. Labroo RB, Paine MF, Thummel KE, Kharasch ED "Fentanyl metabolism by human hepatic and intestinal cytochrome P450 3A4: implicaitons for interindividual variability in disposition, efficacy, and drug interactions." Drug Metab Dispos 25 (1997): 1072-80
  4. "Product Information. Actiq (fentanyl)." Abbott Pharmaceutical, Abbott Park, IL.
  5. Tateishi T, Krivoruk Y, Ueng YF, Wood AJ, Guengerich FP, Wood M "Identification of human cytochrome P-450 3A4 as the enzyme responsible for fentanyl and sufentanil N-dealkylation." Anesth Analg 82 (1996): 167-72
View all 5 references

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Moderate

verapamil food

Applies to: verapamil

GENERALLY AVOID: Consumption of large quantities of grapefruit juice may be associated with significantly increased plasma concentrations of oral verapamil. The mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. One study reported no significant effect of a single administration of grapefruit juice on the pharmacokinetics of verapamil in ten hypertensive patients receiving chronic therapy. In another study conducted in nine healthy male volunteers, administration of 120 mg oral verapamil twice daily for 3 days following pretreatment with 200 mL grapefruit juice twice daily for 5 days resulted in a 57% increase in S-verapamil peak plasma concentration (Cmax), a 36% increase in S-verapamil systemic exposure (AUC), a 40% increase in R-verapamil Cmax, and a 28% increase in R-verapamil AUC compared to administration following orange juice. Elimination half-life and renal clearance of both S- and R-verapamil were not affected by grapefruit juice, and there were no significant effects on blood pressure, heart rate, or PR interval. A third study reported a 1.63-fold increase in Cmax and a 1.45-fold increase in AUC of (R,S)-verapamil in 24 young, healthy volunteers given verapamil sustained-release 120 mg twice daily for 7 days with 250 mL grapefruit juice four times daily on days 5 through 7. Two subjects developed PR interval prolongation of more than 350 ms during grapefruit juice coadministration. A high degree of interindividual variability has been observed in these studies. The interaction was also suspected in a case report of a 42-year-old woman who developed complete heart block, hypotension, hypoxic respiratory failure, severe anion gap metabolic acidosis, and hyperglycemia following accidental ingestion of three verapamil sustained-release 120 mg tablets over a span of six hours. The patient's past medical history was remarkable only for migraine headaches, for which she was receiving several medications including verapamil. Prior to admission, the patient had a 2-week history of poorly controlled migraine, and the six hours preceding hospitalization she suffered from worsening headache and palpitations progressing to altered sensorium. An extensive workup revealed elevated verapamil and norverapamil levels more than 4.5 times above the upper therapeutic limits. These levels also far exceeded those reported in the medical literature for patients taking verapamil 120 mg every 6 hours, or 480 mg in a 24-hour period. The patient recovered after receiving ventilator and vasopressor support. Upon questioning, it was discovered that the patient had been drinking large amounts of grapefruit juice (3 to 4 liters total) the week preceding her admission due to nausea. No other sources or contributing factors could be found for the verapamil toxicity.

MANAGEMENT: Patients treated with oral verapamil should avoid the consumption of large amounts of grapefruit or grapefruit juice to prevent any undue fluctuations in serum drug levels. Patients should be advised to seek medical attention if they experience edema or swelling of the lower extremities; sudden, unexplained weight gain; difficulty breathing; chest pain or tightness; or hypotension as indicated by dizziness, fainting, or orthostasis.

References

  1. Bailey DG, Dresser GK "Natural products and adverse drug interactions." Can Med Assoc J 170 (2004): 1531-2
  2. Ho PC, Ghose K, Saville D, Wanwimolruk S "Effect of grapefruit juice on pharmacokinetics and pharmacodynamics of verapamil enantiomers in healthy volunteers." Eur J Clin Pharmacol 56 (2000): 693-8
  3. Fuhr U, Muller-Peltzer H, Kern R, et al. "Effects of grapefruit juice and smoking on verapamil concentrations in steady state." Eur J Clin Pharmacol 58 (2002): 45-53
  4. Arayne MS, Sultana N, Bibi Z "Review: grape fruit juice - drug interactions." Pak J Pharm Sci 18 (2005): 45-57
  5. McAllister RG, Jr "Clinical pharmacology of slow channel blocking agents." Prog Cardiovasc Dis 25 (1982): 83-102
  6. "Product Information. Covera-HS (verapamil)." Searle, Skokie, IL.
  7. Bailey DG, Malcolm J, Arnold O, Spence JD "Grapefruit juice-drug interactions. 1998." Br J Clin Pharmacol 58 (2004): S831-40; discussion S841-3
  8. Zaidenstein R, Dishi V, Gips M, Soback S, Cohen N, Weissgarten J, Blatt A, Golik A "The effect of grapefruit juice on the pharmacokinetics of orally administered verapamil." Eur J Clin Pharmacol 54 (1998): 337-40
  9. Pillai U, Muzaffar J, Sandeep S, Yancey A "Grapefruit juice and verapamil: a toxic cocktail." South Med J 102 (2009): 308-9
View all 9 references

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Therapeutic duplication warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

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