Bictegravir and Metformin Drug-Drug Interaction in People with Human Immunodeficiency Virus (HIV)

A drug-drug interaction (DDI) exists between bictegravir and metformin. Bictegravir inhibits renal organic cation transporter-2, leading to increased metformin plasma concentrations. The objective of this analysis was to evaluate the clinical implications of concomitant bictegravir and metformin administration. This was a retrospective, single-center, descriptive analysis evaluating people with human immunodeficiency virus (PWH) concurrently prescribed bictegravir and metformin between February 2018-June 2020. PWH lost to follow-up or non-adherent were excluded. Data collection included: hemoglobin A1C (HgbA1C), HIV RNA viral load, CD4 cell count, serum creatinine, and lactate. Adverse drug reactions (ADRs) were assessed by provider-documented, patient-reported symptoms of gastrointestinal (GI) intolerance and hypoglycemia. Metformin dose adjustments and discontinuations were recorded. Fifty-three PWH were included (116 screened; 63 excluded). GI intolerance was reported in three PWH (5.7%). There were no documented episodes of hypoglycemia or lactic acidosis. Five PWH had metformin dose reductions (N = 3 for unspecified reasons; N = 1 for GI intolerance) or discontinuation (N = 1 unrelated to ADRs). Both diabetes and HIV control improved (HgbA1C decreased by 0.7% with virologic control in 95% of PWH). Minimal ADRs were reported in PWH receiving concurrent metformin and bictegravir. Prescribers should be aware of this potential interaction; however, no empiric metformin total daily dose adjustment appears necessary.

Antimicrobial usage at a large teaching hospital in Lusaka, Zambia

Antimicrobial resistance is a growing global health concern. Antimicrobial stewardship (AMS) curbs resistance rates by encouraging rational antimicrobial use. However, data on antimicrobial stewardship in developing countries is scarce. The objective of this study was to characterize antimicrobial use at the University Teaching Hospital (UTH) in Lusaka, Zambia as a guiding step in the development of an AMS program. This was a cross-sectional, observational study evaluating antimicrobial appropriateness and consumption in non-critically ill adult medicine patients admitted to UTH. Appropriateness was defined as a composite measure based upon daily chart review. Sixty percent (88/146) of all adult patients admitted to the general wards had at least one antimicrobial ordered and were included in this study. The most commonly treated infectious diseases were tuberculosis, pneumonia, and septicemia. Treatment of drug sensitive tuberculosis is standardized in a four-drug combination pill of rifampicin, isoniazid, pyrazinamide and ethambutol, therefore appropriateness of therapy was not further evaluated. The most common antimicrobials ordered were cefotaxime (n = 45), ceftriaxone (n = 28), and metronidazole (n = 14). Overall, 67% of antimicrobial orders were inappropriately prescribed to some extent, largely driven by incorrect dose or frequency in patients with renal dysfunction. Antimicrobial prescribing among hospitalized patients at UTH is common and there is room for optimization of a majority of antimicrobial orders. Availability of certain antimicrobials must be taken into consideration during AMS program development.

Vancomycin Pharmacokinetics in Obese Patients with Sepsis or Septic Shock

STUDY OBJECTIVES

Obese patients with sepsis or septic shock may have altered vancomycin pharmacokinetics compared with the general population that may result in improper dosing or inadequate drug concentrations. The objective of this study was to characterize vancomycin pharmacokinetics in obese patients with sepsis or septic shock, and to develop a novel pharmacokinetic dosing model based on pharmacokinetic-pharmacodynamic target requirements.

DESIGN

Prospective observational pharmacokinetic study.

SETTING

Large quaternary academic medical center.

PATIENTS

Sixteen obese (body mass index [BMI] 30 kg/m² or higher) adults with sepsis and either a gram-positive bacteremia or requiring vasopressor support (septic shock), who were receiving vancomycin between November 2016 and June 2018, were included. Patients were excluded if they were receiving renal replacement therapy or extracorporeal membrane oxygenation, treatment for central nervous system infections, pregnant, or receiving vancomycin for surgical prophylaxis.

INTERVENTION

Four blood samples per patient were collected following a single dose of vancomycin: one peak serum vancomycin level (within 1-2 hrs of infusion completion), two random levels during the dosing interval, and one trough level (within 30-60 min of the next dose) were measured.

MEASUREMENTS AND MAIN RESULTS

A population pharmacokinetic model was developed to describe vancomycin concentrations over time. Simulations to determine optimal dosing were performed using the pharmacokinetic model with different ranges of creatinine clearance (Cl_cr ) and different vancomycin daily doses. Median age of the patients was 62 years; median BMI was 36.1 kg/m² , Acute Physiology and Chronic Health Evaluation II score was 26, and Sequential Organ Failure Assessment score was 11. Eleven patients (69%) had an acute kidney injury. Median initial vancomycin dose was 15 mg/kg; median vancomycin trough concentration was 17 mg/L. A one-compartment model best characterized the pharmacokinetics of vancomycin in obese patients with sepsis or septic shock. Volume of distribution was slightly increased in this population (0.8 L/kg) compared with the general population (0.7 L/kg). Only Cl_cr effect on drug clearance was found to be significant (decrease in the objective function value by 16.4 points), confirming that it is a strong predictor of vancomycin clearance.

CONCLUSION

To our knowledge, this study provides the first population-based pharmacokinetic model in obese patients with sepsis or septic shock. The nomograms generated from this pharmacokinetic model provide a simplified approach to vancomycin dosing in this patient population.