PHARMACOKINETIC PARAMETERS OF TRAMADOL AND ITS O-DESMETHYL TRAMADOL
METABOLITE IN POSTOPERATIVE PATIENTS
Abstract
BACKGROUND Tramadol is a unique analgesic because of its serotonin,
gamma-aminobutyric acid (GABA), norepinephrine and opioid effects, as
such, it is famous as a postoperative analgesic; regrettably, it has
gained notoriety as a major source of drug abuse in West Africa. Despite
its licit and illicit popularity, few studies have focused on the
pharmacokinetics of oral tramadol in blacks who reside in Africa. This
study aimed to assess the pharmacokinetic parameters of tramadol in
postoperative patients, a common drug in postoperative pain management.
METHODS AND EXPERIMENTAL APPROACH After ethical clearance and informed
consent, the researcher conducted time kinetics of tramadol and its
metabolite on 12 postoperative patients after a single oral dose of
tramadol at 100 mg. Concentrations of tramadol and its O-desmethyl
tramadol metabolite were assayed using HPLC (UV detection) after
liquid-liquid extraction. The internal standard used was phenacetin.
RESULTS None of the patients experienced severe adverse effects. Data on
validation, robustness, linearity, precision and accuracy for tramadol
and O-desmethyl tramadol were within acceptable limits. Maximum plasma
concentration (Cmax), half-life, and time to reach Cmax for tramadol and
its metabolite were found to be 5.11 ± 2.95 and 4.68 ± 2.9 mg/L; 9.17 ±
6.94 and 5.75 ± 4.52 hours; 4.71 ± 3.77 and 3.38 ± 2.13 hours
respectively. CONCLUSIONS The findings in this study were higher than
the therapeutic level described in previous studies reviewed without any
acute adverse severe effect, further studies are needed in the studied
population to verify these findings.