Background and Importance Pharmacokinetic monitoring is a tool used in therapeutic optimisation to achieve the best clinical results and minimise the incidence of adverse effects.

It is particularly useful in drugs with a dose-dependent clinical response and toxicity relationship and with a narrow therapeutic margin. Computing software are used to integrate patient data into population models through which pharmacists can establish the optimal dosage regimen.

Aim and Objectives To analyse the influence of pharmacokinetic reports on clinical decision.

Material and Methods A retrospective observational study was conducted from January to August 2022 in a general hospital. Patients with at least one plasma concentration of amikacin, amitriptyline, carbamazepine, digoxin, phenytoin, phenobarbital, gentamicin, lithium, theophylline, tobramycin, valproic acid, and vancomycin were included.

Collected data included gender, age, weight, height, serum creatinine, drug, dosage, plasma concentrations and concomitant medication.

A pharmacokinetic software was used. By Bayesian estimation, optimal dosage regimen was calculated. Based on these data, the pharmacist prepared the pharmacokinetic report and dosage recommendations for the physician.

Recommendations made by the pharmacist were recorded and classified according to following criteria: Underdosing, intoxication, no adjustment required, lack of adherence and interaction adjustment. The percentage of acceptance of the interventions was analysed.

Results 182 patients and 395 interventions were evaluated.

Clinical services that received more pharmacokinetic reports were internal medicine (48%) and psychiatry (19%). The most common monitored drugs were digoxin (24%), valproic acid (22%) and vancomycin (18%).

In 21% of the patients adjustments were made due to underdosing, 13% due to overdosing, 4% due to lack of adherence, and 2% due to drug-drug interactions. There was no need to adjust dosage in 40% of monitored patients. The remaining 20% were interventions related to errors in the extraction of the analytics.

71% of the recommendations addressed to physicians were accepted.

Conclusion and Relevance The most common dosage adjustment was due to underdosing so that the efficacy of the treatment was compromised. It should also be noted that there is a high percentage of errors in the analytic extraction procedure. Health professionals who perform the sample collection must be properly trained.

Clinical pharmacokinetics is a tool that allows us to optimise the patient‘s dosage regimen.

Conflict of Interest No conflict of interest