Preemptive warfarin dose reduction after initiation of sulfamethoxazole-trimethoprim or metronidazole

Antibiotic-Drug Interactions in the Intensive Care Unit: A Literature Review

Interactions between drugs are a common problem in Intensive Care Unit patients, as they mainly have a critical condition that often demands the administration of multiple drugs simultaneously. Antibiotics are among the most frequently used medications, as infectious diseases are often observed in ICU patients. In this review, the most important antibiotic-drug interactions, based on the pharmacokinetic and pharmacodynamic mechanisms, were gathered together and described. In particular, some of the most important interactions with main groups of antibacterial drugs were observed in patients simultaneously prescribed oral anticoagulants, NSAIDs, loop diuretics, and valproic acid. As a result, the activity of drugs can be increased or decreased, as dosage modification might be necessary. It should be noted that these crucial interactions can help predict and avoid negative consequences, leading to better patient recovery. Moreover, since there are other factors, such as fluid therapy or albumins, which may also modify the effectiveness of antibacterial therapy, it is important for anaesthesiologists to be aware of them.

Drug Interactions Affecting Oral Anticoagulant Use

Oral anticoagulants (OACs) are medications commonly used in patients with atrial fibrillation and other cardiovascular conditions. Both warfarin and direct oral anticoagulants are susceptible to drug-drug interactions (DDIs). DDIs are an important cause of adverse drug reactions and exact a large toll on the health care system. DDI for warfarin mainly involve moderate to strong inhibitors/inducers of cytochrome P450 (CYP) 2C9, which is responsible for the elimination of the more potent S-isomer of warfarin. However, inhibitor/inducers of CYP3A4 and CYP1A2 may also cause DDI with warfarin. Recognition of these precipitating agents along with increased frequency of monitoring when these agents are initiated or discontinued will minimize the impact of warfarin DDI. Direct oral anticoagulants are mainly affected by medications strongly affecting the permeability glycoprotein (P-gp), and to a lesser extent, strong CYP3A4 inhibitors/inducers. Dabigatran and edoxaban are affected by P-gp modulation. Strong inducers of CYP3A4 or P-gp should be avoided in all patients taking direct oral anticoagulant unless previously proven to be otherwise safe. Simultaneous strong CYP3A4 and P-gp inhibitors should be avoided in patients taking apixaban and rivaroxaban. Concomitant antiplatelet/anticoagulant use confers additive risk for bleeding, but their combination is unavoidable in many cases. Minimizing duration of concomitant anticoagulant/antiplatelet therapy as indicated by evidence-based clinical guidelines is the best way to reduce the risk of bleeding.

The Relationship Among Intestinal Bacteria, Vitamin K and Response of Vitamin K Antagonist: A Review of Evidence and Potential Mechanism

The vitamin K antagonist is a commonly prescribed effective oral anticoagulant with a narrow therapeutic range, and the dose requirements for different patients varied greatly. In recent years, studies on human intestinal microbiome have provided many valuable insights into disease development and drug reactions. A lot of studies indicated the potential relationship between microbiome and the vitamin K antagonist. Vitamin K is absorbed by the gut, and the intestinal bacteria are a major source of vitamin K in human body. A combined use of the vitamin K antagonist and antibiotics may result in an increase in INR, thus elevating the risk of bleeding, while vitamin K supplementation can improve stability of anticoagulation for oral vitamin K antagonist treatment. Recently, how intestinal bacteria affect the response of the vitamin K antagonist remains unclear. In this review, we reviewed the research, focusing on the physiology of vitamin K in the anticoagulation treatment, and investigated the potential pathways of intestinal bacteria affecting the reaction of the vitamin K antagonist.

Preemptive Dose Adjustment Effect on the Quality of Anticoagulation Management in Warfarin Patients With Drug Interactions: A Retrospective Cohort Study

One strategy to manage patients on warfarin starting an interacting drug is to increase the frequency of monitoring. Another strategy is to adjust warfarin dose around the time patient is started on an interacting medication, which is known as “preemptive warfarin dose adjustment.” The main objective of this study is to compare preemptive to nonpreemptive strategy and their impact on the quality of anticoagulation management. This is a retrospective cohort study performed at the pharmacist-managed anticoagulation clinic in a tertiary hospital in the State of Qatar. Over a 4-year period, 340 patients were evaluated, and 58 warfarin–drug interaction encounters were identified. Mean age of the patients was (57.7 ± 13.7), and 50% of them were females. Preemptive dose adjustment was used in 17 (29.3%) cases. Incidence of out-of-target international normalized ratio (INR) was statistically lower in the preemptive arm compared to the control group (41.2% [7/17] vs 69.2% [27/39], P = .048). Incidence of extreme out-of-target INR was numerically lower in the preemptive arm compared to the control but did not reach statistical significance (11.8% [2/17] vs 29.3% [12/41], P = .139). Change in frequency of INR monitoring was not different between the 2 groups. However, overall frequency of INR monitoring after onset/discontinuation of interacting medication increased compared to baseline (7 [9] vs 21 [16] days, P < .001). Preemptive strategy was shown in our study to decrease incidence of the out-of-target INR visits, although patients remained in need for close monitoring.

Drug-drug interactions in an era of multiple anticoagulants: a focus on clinically relevant drug interactions

Oral anticoagulants are commonly prescribed but high risk to cause adverse events. Skilled drug interaction management is essential to ensure safe and effective use of these therapies. Clinically relevant interactions with warfarin include drugs that modify cytochrome 2C9, 3A4, or both. Drugs that modify p-glycoprotein may interact with all direct oral anticoagulants, and modifiers of cytochrome 3A4 may interact with rivaroxaban and apixaban. Antiplatelet agents, nonsteroidal anti-inflammatory drugs, and serotonergic agents, such as selective serotonin reuptake inhibitors, can increase risk of bleeding when combined with any oral anticoagulant, and concomitant use should be routinely assessed. New data on anticoagulant drug interactions are available almost daily, and therefore, it is vital that clinicians regularly search interaction databases and the literature for updated management strategies. Skilled drug interaction management will improve outcomes and prevent adverse events in patients taking oral anticoagulants.

Drug-drug interactions in an era of multiple anticoagulants: a focus on clinically relevant drug interactions

Oral anticoagulants are commonly prescribed but high risk to cause adverse events. Skilled drug interaction management is essential to ensure safe and effective use of these therapies. Clinically relevant interactions with warfarin include drugs that modify cytochrome 2C9, 3A4, or both. Drugs that modify p-glycoprotein may interact with all direct oral anticoagulants, and modifiers of cytochrome 3A4 may interact with rivaroxaban and apixaban. Antiplatelet agents, nonsteroidal anti-inflammatory drugs, and serotonergic agents, such as selective serotonin reuptake inhibitors, can increase risk of bleeding when combined with any oral anticoagulant, and concomitant use should be routinely assessed. New data on anticoagulant drug interactions are available almost daily, and therefore, it is vital that clinicians regularly search interaction databases and the literature for updated management strategies. Skilled drug interaction management will improve outcomes and prevent adverse events in patients taking oral anticoagulants.