Abstracts

Rationale: The efficacy or adverse reaction of phenobarbital is influenced by personal variability and recall bias, which can be assessed by blood concentration determination. This retrospective study evaluated the relationship between phenobarbital blood concentration and its efficacy in people with epilepsy to seek a new indicator to guide treatment. Methods: We carried out follow-up assessments of people who took part in the feasibility study of the Global Campaign Against Epilepsy in rural areas of China. People with epilepsy who were treated with phenobarbital monotherapy were recruited and followed up for about 2.5 years. Information was collected using a standardized questionnaire by face-to-face interviews of the individuals (and their families where necessary). Phenobarbital plasma concentrations were detected by high-performance liquid chromatographic (HPLC). Results: Two hundred fifty-five people were included in the study and information on treatment response was obtained in 240 (94.12%). Among them, 128 (53.3%) were recognized as improved cases with a phenobarbital plasma concentration median at 13.41µg/ml. However, the concentration median of ineffective patients was 20.02µg/ml, which was higher than the effective one (P<0.0001). Multivariate logistic regression analysis showed that phenobarbital blood concentration = 26.83 µg/ml was 3.1-fold risk of inefficacy, and no significant difference was observed between other concentration intervals. Conclusions: In conclusion, the effective rate of phenobarbital not always grew with the increase of the plasma concentration. Once the threshold is reached, better efficacy cannot be obtained just by the increase of dosage. Accordingly, blood concentration is an important indicator for clinical decision making when phenobarbital monotherapy cannot reach a seizure free. Further study is needed to determine the exact value of threshold. Funding: None