Related Experiment Video
Updated: Jun 17, 2026
09:25
Methods to Evaluate Cytotoxicity and Immunosuppression of Combustible Tobacco Product Preparations
Published on: January 10, 2015
Probable warfarin interaction with menthol cough drops
Karen Coderre1, Claudio Faria, Earl Dyer
1Clinical Pharmacy Services, University of Massachusetts Medical School, Commonwealth Medicine, Shrewsbury, MA, USA.
Pharmacotherapy
|December 25, 2009
Summary
Menthol cough drops can decrease the effectiveness of warfarin, an anticoagulant. Patients taking warfarin should be cautious of over-the-counter products like menthol cough drops due to potential drug interactions.
Area of Science:
- Pharmacology
- Clinical Medicine
- Drug Interactions
Background:
- Warfarin is a common oral anticoagulant with a known risk of drug and food interactions.
- Maintaining a therapeutic international normalized ratio (INR) is crucial for patients on warfarin therapy.
Observation:
- A 46-year-old man on warfarin for venous thromboembolism experienced a significant decrease in INR.
- This decrease occurred despite no changes in his warfarin dosage, diet, or other medications.
- The patient reported daily use of menthol cough drops for workplace-induced dry conditions.
Findings:
- Discontinuation of menthol cough drops led to a rapid increase in the patient's INR from 1.6 to 2.9.
- The patient's weekly warfarin dose was subsequently reduced from 50 mg to 40 mg to maintain therapeutic INR.
- The Naranjo scale indicated a probable link between menthol cough drop use and the reduced INR.
Implications:
- Menthol may interact with warfarin metabolism, potentially via the cytochrome P450 system.
- This case highlights the importance of monitoring patients on warfarin for interactions with over-the-counter products.
- Healthcare providers should counsel patients on potential interactions with menthol-containing products.
Related Concept Videos
01:18Anticoagulant Drugs: Vitamin K Antagonists and Direct Oral Anticoagulants
Oral anticoagulants are vital tools in preventing and treating blood clotting disorders. This diverse class of medications can be categorized as vitamin K antagonists, exemplified by warfarin, and direct thrombin inhibitors (DTIs), such as dabigatran, as well as factor Xa inhibitors, including rivaroxaban.
Warfarin, a prominent vitamin K antagonist family member, exerts its effect by inhibiting the enzyme VKORC1 (vitamin K epoxide reductase complex 1). By hindering this enzyme, warfarin...
Warfarin, a prominent vitamin K antagonist family member, exerts its effect by inhibiting the enzyme VKORC1 (vitamin K epoxide reductase complex 1). By hindering this enzyme, warfarin...
01:30Drug toxicity: Drug–Drug Interaction
Drug–drug interactions can precipitate toxicity through multiple mechanisms. Absorption interactions alter how drugs enter the body, exemplified when ranitidine increases the absorption of basic drugs, while cholestyramine decreases the levels of propranolol. Protein binding interactions occur when drugs share the same binding sites on plasma proteins. Drugs like aspirin and warfarin, when bound in excess, can lead to increased free drug concentrations, enhancing the potential for...
01:30Anticoagulant Drugs: Low-Molecular-Weight Heparins
Hemostasis is a crucial process that prevents excessive blood loss from damaged blood vessels. It involves various mechanisms such as vasoconstriction, platelet adhesion and activation, and fibrin formation. The importance of each mechanism depends on the type of vessel injury. In contrast, thrombosis is the abnormal formation of a blood clot within the blood vessels, leading to potential complications if the clot obstructs blood flow. Thrombosis can be caused by increased coagulability of the...
01:26Pharmacokinetics: Drug–Food and Drug–Viral Interactions
A drug interaction occurs when the concurrent use of another drug, food, or an external substance alters the pharmacological activity of a drug. This interaction can modify the action of the original drug, affecting its effectiveness and safety.Drug–food interactions are significant as they impact drug absorption, metabolism, and excretion. For example, grapefruit juice is a well-known disruptor of drug metabolism. It inhibits the cytochrome P450 3A4 enzyme, crucial for the metabolism of many...
01:25Pharmacokinetics: Drug–Drug Interactions
Drug interactions occur when the pharmacological effect of one drug is altered by another substance, either enhancing or diminishing its activity. The drug whose activity is altered is known as the object drug, and the substance causing the alteration is called the agent drug or the precipitant. The net effects of these interactions are mostly undesirable, leading to decreased effectiveness or increased adverse effects. In rare cases, interactions can be beneficial, such as the enhanced...
01:29Venous Thrombosis III: Interprofessional Care
Venous thrombosis requires effective prevention and treatment strategies to improve patient outcomes and reduce potential complications.Prevention StrategiesHealthcare providers must prioritize preventing venous thromboembolism (VTE) for all adult patients upon admission. Interventions depend on bleeding and thrombosis risk, medical history, current medications, diagnoses, planned procedures, and patient preferences. Patients on bed rest should change positions every two hours and, if not...