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Drug Interactions between halofantrine and tacrine

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

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Interactions between your drugs

Moderate

tacrine halofantrine

Applies to: tacrine and halofantrine

MONITOR: Acetylcholinesterase inhibitors may have vagotonic effects on the sinoatrial and atrioventricular nodes, which occasionally manifest as bradycardia or heart block (<2%). Because bradycardia is a risk factor for torsade de pointes, a theoretical risk exists when combined with agents that prolong the QT interval. 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 including, but not limited to congenital long QT syndrome, cardiac disease, and electrolyte disturbances (e.g., hypokalemia, hypomagnesemia). In addition, the extent of drug-induced QT prolongation may vary depending on the dosage(s) and specific drug(s) involved.

MANAGEMENT: Caution is advised when acetylcholinesterase inhibitors are used with drugs that can prolong the QT interval. Patients should be monitored for bradycardia, atrioventricular block and syncope, and advised to seek medical attention if they experience dizziness, lightheadedness, fainting, shortness of breath, or slow or irregular heartbeat.

References (12)
  1. (2001) "Product Information. Aricept (donepezil)." Pfizer U.S. Pharmaceuticals
  2. (2001) "Product Information. Exelon (rivastigmine)." Novartis Pharmaceuticals
  3. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  4. Canadian Pharmacists Association (2006) e-CPS. http://www.pharmacists.ca/function/Subscriptions/ecps.cfm?link=eCPS_quikLink
  5. Cerner Multum, Inc. "Australian Product Information."
  6. (2024) "Product Information. Galantamine Hydrobromide ER (galantamine)." Aurobindo Pharma USA Inc
  7. (2024) "Product Information. Galantamine Hydrobromide (galantamine)." Aurobindo Pharma USA Inc
  8. (2022) "Product Information. Gaalin (galantamine)." Auro Pharma Inc
  9. (2023) "Product Information. Galzemic (galantamine)." Zentiva Pharma UK Ltd
  10. (2023) "Product Information. Galantyl (galantamine)." Viatris UK Healthcare Ltd
  11. (2020) "Product Information. Auro-Galantamine ER (galantamine)." Auro Pharma Inc
  12. (2024) "Product Information. Zunveyl (benzgalantamine)." Alpha Cognition, Inc., SUPPL-1

Drug and food interactions

Major

halofantrine food

Applies to: halofantrine

GENERALLY AVOID: Grapefruit juice may increase the plasma concentration of halofantrine. The mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. After administration of 500 mg with 250 mL regular-strength grapefruit juice daily for 3 days, average halofantrine AUC increased 2.8-fold and peak plasma concentrations increased 3.2-fold, compared to water, in healthy subjects (n=12). QT interval prolongation increased from an average of 17 ms with water to 31 ms with grapefruit juice. Halofantrine, even at recommended doses, can cause dose-related prolongation of the QT interval, resulting in an elevated risk of potentially fatal ventricular arrhythmias including ventricular tachycardia and torsade de pointes.

ADJUST DOSING INTERVAL: The presence of food may increase the absorption and toxicity of halofantrine. Peak plasma concentrations increased seven-fold and AUC increased three-fold in healthy subjects when halofantrine was administered with high-fat food.

MANAGEMENT: The authors of the study recommend that grapefruit juice be avoided during halofantrine therapy. The manufacturer recommends performing an ECG before initiating halofantrine therapy and cardiac monitoring during and for 8 to 12 hours after completion of therapy. Halofantrine should be taken on an empty stomach at least 1 hour before or 2 hours after food.

References (4)
  1. Giao PT, de Vries PJ (2001) "Pharmacokinetic interactions of antimalarial agents." Clin Pharmacokinet, 40, p. 343-73
  2. (2003) "Product Information. Halfan (halofantrine)." GlaxoSmithKline
  3. Charbit B, Becquemont L, Lepere B, Peytavin G, Funck-Bretano C (2002) "Pharmacokinetic and pharmacodynamic interaction between grapefruit juice and halofantrine." Clin Pharmacol Ther, 72, p. 514-23
  4. Abernethy DR, Wesche DL, Barbey JT, et al. (2001) "Stereoselective halofantrine disposition and effect: concentration-related QTc prolongation." Br J Clin Pharmacol, 51, p. 231-7

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.

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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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