Prescription Optimization through Pharmacokinetic Analyses of Patients with Side Effects

Abstract

Since clinical pharmacists provide support for pharmacotherapy, pharmacists sometimes encounter unknown side effects and drug interactions. However, by involving pharmacological concepts to establish rules from patients experiencing side effects, adverse effects can be reduced or avoided. In this paper, ways to optimize prescriptions using pharmacokinetic analyses of absorption, distribution, metabolism and excretion in patients who had experienced side effects will be introduced. First, in the absorption phase, the effects of gastrectomy on pharmacokinetic profiles and side effects of oral etoposide were found. Second, in order to prevent diarrhea, which is a major side effect of irinotecan, orally administering Kremezin ® to adsorb SN-38, was found effective. In addition, in the distribution phase, the mechanism of interaction between lidocaine and mexiletine during tissue distribution was found. In the metabolism phase, a drug interaction mechanism between theophylline and acyclovir was found. By comparing the ratio between the serum concentration of SN-38G and SN-38, evaluating metabolic capacity rather than UDP-glucuronosyltransferase (UGT) 1A1 polymorphism was found more useful for patients treated with irinotecan. In the excretion phase, a method of drug administration based on creatinine clearance was established, since if treatment with renally excreted medications such as cibenzoline, ribavirin, and vancomycin is performed in accordance with the dosage regimen in the package insert of these drugs, cibenzoline causes hypoglycemia, ribavirin causes anemia, and vancomycin causes renal failure. By clarifying the mechanism of side effects using pharmacokinetics, improving the therapeutic effect by reducing or preventing side effects in the clinical setting is possible.