Laboratory markers in personalized drug therapy

Abstract

During the last decade two major trends have influenced the thinking about the benefit-risk balance in drug therapy.The first trend showed that this balance is not only determined by the interaction of the pharmacological properties of the drug with the patient’s (patho)physiological profile, but is also to a large extent modulated by the way the drug is handled by healthcare providers and by the patient. Medication errors have shown to be a major factor in drug induced harm and system flaws particularly contribute to these. It has triggered on national and international levels the development of mandatory risk evaluation and mitigation strategies. The second trend regards the paradigm shift in pharmacy from a drug oriented approach towards a patient oriented approach, because each individual reacts differently on drug therapy. In the pharmacy setting this induced and further requires major changes in the pharmaceutical care process. For healthcare providers laboratory markers are considered important patient factors for taking evidence based decisions on drug effectiveness, risk of adverse events, medication adherence or medical necessity of a drug. Studies in this thesis show the necessity of laboratory monitoring in drug therapy. An average of 2.8 instructions on laboratory monitoring per drug label was found. However, these instructions were incomplete and the clinical applicability was limited. In the clinical risk management of potential drug-drug interactions laboratory markers (renal function, electrolytes and coagulation) are required in 9% of the patients. Other studies focus on the development and execution of risk management strategies in patients with impaired renal function. One strategy was the use of a pharmacy medication alert system that specifically assessed the appropriateness of prescribed dosage regimens based on an actual renal function in high risk patients. The general practitioner adjusted drug therapy in 6% of the elderly patients after advice of the pharmacist. Linking laboratory data to medical and pharmacy data is essential to manage effectively these interactions. Another strategy focused on the feasibility of point-of-care creatinine testing in community pharmacy in patients at risk for chronic kidney disease. In 44% of these patients renal function was unknown. Point-of-care testing was found to have added value for effective drug therapy management because an actual renal function was measured at the moment the patient visited the pharmacy. Multidisciplinary collaboration of physicians, pharmacists and clinical chemists is a key issue in these strategies. Finally, studies on the effects of drugs on laboratory test results show that there is enough evidence of these effects in drug labels but that the information given was incomplete. Access to linked health records offers clinical chemists the opportunity to advise other healthcare professionals about the risks of drug effects. In conclusion, the findings from the studies presented have demonstrated that laboratory markers are important in personalized drug therapy. By monitoring only risks with proven clinical validity and clinical utility in patients at high risk, the use of laboratory markers will lead to improved medication safety and evidence based monitoring by assessing the benefit-risk balance for the individual patient.