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Introduction: Circadian variations in biological rhythms affect the pharmacological properties of many anaesthetic agents, suggesting circadian patterns of local anaesthetics’ activity in labour pain analgesia, with important differences among diurnal and nocturnal phases.Aim: We examined whether a rhythmic variation of the effect of intrathecal mixture of levobupivacaine and fentanyl exists throughout the day period regarding caesarean sections. Materials and methods: Eighty parturients presented for caesarean section, both urgent and/or elective, were assigned to five equal groups (A, B, C, D, and E) according to the time-point of the intrathecal drug administration. The same levobupivacaine and fentanyl dose was given to all patients. Pinprick or cold test, the four-point modified Bromage scale (0-3), and the numerical scale (NRS 0-10) were used respectively for the assessment of sensory and motor blockade, and post-anaesthetic pain. The duration of sensory and motor blockade, analgesia duration and pain score at first analgesic request were recorded.Results: Statistically significant differences were found among the studied groups in the duration of motor and sensory blockade and pain score at first postoperative analgesic request. Prolonged duration of motor blockade in groups A, B and C (p