Interference of pregnancy steroid hormones with FPN test for estimation of phenothiazine derivatives in urine.

Interference of pregnancy steroid hormones with FPN test for estimation of some phenothiazine derivatives in urine has been investigated. The FPN test was positive in 97.9% of urine samples obtained from pregnant women. It is supposed that metabolites of estrogens and progestagens present in higher amounts in urine samples of these women are responsible for this positivity.