Assessment of an online calculator's vancomycin dosing and exposure appropriateness in persons who inject drugs with methicillin-resistant Staphylococcus aureus bloodstream infections.

WHAT IS KNOWN AND OBJECTIVE: While the gold standard for calculating AUC involves two steady-state concentrations, online calculators can empirically estimate AUC and other pharmacokinetic (PK) parameters. In patients with potentially altered PK, such as persons who inject drugs (PWID), the reliability of these predictions is unclear. Our objectives were to characterize the PK of vancomycin in PWID with methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections (BSI) and to assess the impact of these PK parameters on dosing regimens when compared to regimens generated by an online calculator. METHODS: This descriptive pilot study included a retrospective chart review of 48 inpatient PWID with MRSA BSI from 30 April 2018 through 31 August 2020. Demographic and clinical data along with vancomycin dosing and serum concentrations were collected. Patient-specific PK parameters were used to calculate the AUC of each empiric regimen compared with the originally predicted AUC. RESULTS AND DISCUSSION: The study population had a median volume of distribution of 0.74 L/kg, clearance of 0.081 L/kg/h, elimination rate constant of 0.110/h and half-life of 6.3 h. The online calculator empirically predicted 6 subtherapeutic and 42 appropriate AUC values with its recommended empiric dosing regimens. Using the actual patient-specific PK parameters, the empiric vancomycin regimens actually resulted in 21 (43.75%) underexposures, 24 (50%) appropriate exposures and 3 (6.25%) overexposures. WHAT IS NEW AND CONCLUSIONS: In PWID, empiric vancomycin dosing strategies suggested by an online calculator frequently resulted in lower-than-predicted vancomycin exposures. These findings suggest that PWID with MRSA BSI may require higher and/or more frequent vancomycin doses than those empirically recommended by the population-based methods of an online calculator.

The Potential Clinical Implications and Importance of Drug Interactions Between Anticancer Agents and Cannabidiol in Patients With Cancer.

The objective of this review was to identify and examine the pharmacokinetic and pharmacodynamic interactions between cannabidiol (CBD)-only products, such as CBD oil, and anticancer agents. A literature search of PubMed (1980 to September 2018) and the Cochrane Collection (1980 to September 2018) was performed using the following search terms: "cannabidiol," "cancer," "cannabis," "marijuana," and "interaction," as well as any combination of these terms. Literature was excluded if it did not appear in the search when limited to the "full text" filter on PubMed, if it was not published in the English language, or if it did not explore potential pharmacodynamic or pharmacokinetic interactions of CBD and anticancer agents. There were 10 studies that met these inclusion criteria. The majority of the facts regarding the interactions with CBD were found using in vitro studies and the true in vivo implications are not well-known. Minimal data were available regarding the interactions between CBD and anticancer agents. However, pharmacists should always consider the possibility of interactions and their consequences whenever they are aware of a patient using CBD products.