Related Experiment Video
Updated: May 19, 2026
11:15
Quadruple-Checkerboard: A Modification of the Three-Dimensional Checkerboard for Studying Drug Combinations
Published on: July 24, 2021
A probable clinically significant interaction between warfarin and cloxacillin: three case reports.
Hossein Khalili1, Naemeh Nikvarz, Farhad Najmeddin
1Department of Clinical Pharmacy, Faculty of Pharmacy, Tehran University of Medical Sciences, PO Box 14155/6451, Tehran 1417614411, Iran. khalilih@tums.ac.ir
European Journal of Clinical Pharmacology
|September 5, 2012
Summary
Cloxacillin therapy for infective endocarditis can reduce warfarin
Area of Science:
- Infectious Diseases
- Pharmacology
- Cardiology
Background:
- Bacterial endocarditis requires effective antibiotic treatment.
- Anticoagulant therapy, often with warfarin, is crucial for patients with valvular heart disease or prosthetic valves.
- Managing concurrent infections and anticoagulation presents clinical challenges.
Observation:
- Three patients with bacterial endocarditis requiring valve replacement and anticoagulation received cloxacillin.
- Cloxacillin administration led to a significant reduction in warfarin's anticoagulation effect.
- Increased warfarin doses were insufficient to counteract the diminished anticoagulation.
Findings:
- Penicillinase-resistant penicillins, like cloxacillin, are vital for treating Staphylococcus aureus infections.
- A clinically significant drug interaction exists between cloxacillin and warfarin.
- Warfarin anticoagulation efficacy is compromised during cloxacillin treatment for endocarditis.
Implications:
- Clinicians should monitor anticoagulation closely in patients receiving cloxacillin and warfarin concurrently.
- Alternative anticoagulants, such as low-molecular-weight heparin or unfractionated heparin, may be preferable in patients with infective endocarditis requiring anticoagulation.
- This interaction highlights the importance of considering antibiotic-anticoagulant pharmacodynamics in complex patient management.
Related Concept Videos
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...
01:18Anticoagulant 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...
01:26Pharmacokinetics: 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...
01:30Drug 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...
01:27Combined Effects of Drugs: Synergism
Synergism is a useful mechanism where combining two or more drugs is more effective than each constituent used alone. Such combinations are also called supra-additive interactions. The drugs collectively enhance the final therapeutic effect by acting on different targets. Another advantage is that the low dose of each constituent drug is sufficient to achieve the desired effect. This helps reduce the duration of therapy and lower the adverse effects of these drugs.
Such synergistic combinations...
Such synergistic combinations...
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...