Children on phenobarbital monotherapy requires more sedatives during MRI

Background: Phenobarbital induces specific hepatic cytochrome P-450 enzyme pathways causing increased clearance of hepatically metabolized drugs. In this study, we investigated the duration and additional anesthetic requirement during Magnetic resonance imaging (MRI) in epileptic children with or without phenobarbital monotherapy. Methods: In ASA I-II, 128 children, aged 1-10 years, were included. Group I: epileptic children without anti-epileptic therapy and Group II: children with phenobarbital monotherapy. The initial sedative drugs were 0.1 mg·kg ^-1 midazolam with 2 mg·kg ^-1 ketamine. An additional 1 mg·kg ^-1 ketamine was administrated if required. Rescue propofol (0.5 mg·kg ^-1) was provided and repeated to maintain sedation. The duration and consumption of additional sedative requirements was recorded. Results: The duration of initial and two consequent additional sedative requirements was shorter in Group II (P = 0.0001, P = 0.001 and P = 0.27, respectively). Additional ketamine doses required for adequate sedation were lower in Group I (P = 0.016). Conclusion: We suggest that the variability in response to the initial sedative agents during MRI requires titration of additive sedation with ketamine in epileptic children on phenobarbital monotherapy.