Qom University of Medical Sciences Journal

Background and objectives: In chronopharmacology the biological rhythm variations caused
by drug administration is assessed. Evaluation of the time of drug administration and the
qualitative and quantitative effects of reactions to drugs is called chronopharmacodynamics. In
this study, we assessed the chronopharmacodynamics of intrathecal co-administration of
sufentanyl and bupivacaine in surgical operations of lower extremities.
Methods: In 2006, patients aged 20-50 with ASA physical status of I and II, who underwent
surgical operation of lower extremities were entered into this prospective study. The patients
received a slow intrathecal injection of 10 μg sufentanyl and 15 mg bupivacaine into
subarachnoid of third and fourth lumbar spaces in 30 seconds. After the operation, the time of
first pain sensation and the visual analogue scale (VAS) score, as the measure of severity of
pain, were recorded.
Results: 115 patients were studied in this project. The pain-free interval was considered as
the time between injection and patient’s demand for pain relief. This interval was 746 (± 322)
minutes. The average score of pain severity on VAS at the time of demand for pain relief was
24.7 (± 9.3). The average pain-free duration in patients injected about noon or at midnight
was significantly longer than the pain-free interval of other patients.
Conclusion: The results show that intrathecal co-administration of sufentanyl and
bupivacaine at noon or midnight (conforming to the circadian rhythm) causes better painrelief
with longer duration in comparison with other times of the day or night.