Possible Interaction: Phenobarbital and Progesterone

“The opposite actions were selective; phenobarbital raised the oxidative pathway of progesterone metabolism but did not modify the reductive pathway.”

“Accordingly, pretreatment of rats with phenobarbital decreases the uterotropic action of estradiol and estrone, the growth‐promoting effect of testosterone on the seminal vesicles, and the anesthetic action of progesterone and deoxycorticosterone.”

“Conclusion:3-Methylcholanthrene, phenobarbital or dexamethasone could interfere with the synthesis of cortisol, aldosterone and progesterone in primary human fetal adrenal cortical cells, which likely act through xenobiotic metabolizing-related cytochrome P450 isoform activation.”

“Cortisol, aldosterone and progesterone concentrations were also slightly decreased with phenobarbital.”

“Human granulosa cell progesterone synthesis was also inhibited in a dose dependent fashion by phenobarbital , secobarbital and barbituric acid.”

“Screening drugs used in obstetrical practice for effects on steroid hormone synthesis revealed that phenobarbital inhibited progesterone synthesis in MA-10 Leydig tumor cells.”

“Injection of 1 mg progesterone concurrent with phenobarbital restored the first surge of LH but not FSH and partially restored the second peak of serum FSH; the ovaries contained newly formed corpora lutea and 10.5 stage IV follicles per ovary.”

“This opposing hepatic action showed selectivity; phenobarbital increased the oxidative pathway of progesterone metabolism (formation of 6 beta-, 16 alpha-, 20 alpha-hydroxyprogesterone) but the reductive pathway remained unaltered (formation of pregnanediol, pregnanolone).”

“The anesthetic action of large doses of progesterone is inhibited in rats pretreated with DDT, chlordane and phenobarbital (Conney et al. 1966).”

“Administration of phenobarbital at 1100 prevented the LH surge and ovulation from occurring; however, if progesterone was injected 1 hr prior to the phenobarbital , most rats ovulated.”

“It is concluded that the phenobarbital and progesterone exert their reciprocal actions on the pituitary either outside the hypothalamus or on the synaptic thresholds within the hypothalamus.”

“The results described in this paper suggest that phenobarbital is inhibiting the dehydrogenation step in the conversion of pregnenolone to progesterone.”