Polypharmacy is common among older people admitted to general medical units of Australian hospitals, with no clinically meaningful change to the number or classification (symptom control, prevention or both) of drugs made by treating physicians.
Minimising the harm from inappropriate prescribing in older populations is a major urgent concern for modern healthcare systems. In everyday encounters between prescribers and patients, opportunities should be taken to identify patients at high risk of harm from polypharmacy and reappraise their need for specific drugs. Attempts to reconcile life expectancy, comorbidity burden, care goals and patient preferences with the benefits and harms of medications should be made in every patient at significant risk. Drugs identified by this process of reconciliation as conferring little or no benefit and/or excessive risk of harm should be candidates for discontinuation. Evidence supporting a structured approach to drug discontinuation (or deprescribing) is emerging, and while many barriers to deprescribing exist in routine practice, various enabling strategies can help overcome them.
The current approach for therapeutic drug monitoring in renal transplant recipients receiving mycophenolate mofetil (MMF) is measurement of total mycophenolic acid (MPA) concentration. Because MPA is highly bound, during hypoalbuminemia the total concentration no longer reflects the free (pharmacologically active) concentration. The authors investigated what degree of hypoalbuminemia causes a significant change in protein binding and thus percentage free MPA. Forty-two renal transplant recipients were recruited for the study. Free and total concentrations of MPA (predose, and 1, 3, and 6 hours post-MMF dose samples) and plasma albumin concentrations were determined on day 5 posttransplantation. Six-hour area under the concentration-time curve (AUC(0-6)) values were calculated for free and total MPA, and percentage free MPA was determined for each patient. The authors found a significant relationship between low albumin concentrations and increased percentage free MPA (Spearman correlation = -0.54, P < 0.0001). Receiver operating characteristic (ROC) curve analysis was performed on the albumin versus percentage free MPA data. The cutoff value of albumin determined from the ROC analysis that differentiated normal from elevated percentage free MPA (defined as > or = 3%) in this patient population was 31 g/L. At this cutoff value albumin was found to be a good predictor of altered free MPA percentage, with a sensitivity and specificity of 0.75 and 0.80, respectively, and an area under the ROC curve of 0.79. To rationalize MMF dosing regimens in hypoalbuminemic patients (plasma albumin < or = 31 g/L), clinicians should consider monitoring the free MPA concentration.
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