Pharmacokinetic Interactions between the Hormonal Emergency Contraception, Levonorgestrel (Plan B), and Efavirenz

Table 1

Estimated LNG PK parameters.

PK parameter	Percent change raw scale (95% CI)	LNG GM (90% CI)	LNG + EFV GM (90% CI)	𝑃 value	GMR (90% CI)
AUC12 (ng*hr/mL)	−56% (−49%, −62%)	42.9 (38.0, 48.5)	17.8 (15.5, 20.5)	<0.0001	0.42 (0.36, 0.48)
𝐶max (ng/mL)	−41% (−33%, −50%)	8.4 (7.6, 9.3)	4.6 (4.0, 5.4)	<0.0001	0.55 (0.49, 0.63)
𝐶min (ng/mL)	−67% (−59%, −74%)	2.04 (1.7, 2.3)	0.6 (0.5, 0.7)	<0.0001	0.31 (0.26, 0.36)
V/F (L)	110% (−155%, 176%)	144 (120, 173)	256 (217, 301)	0.0001	—
CL/F (L/hr)	260% (159%, 364%)	9.7 (8.0, 11.6)	32.1 (27.6, 37.3)	<0.0001	—
𝑡1/2 (hr)	−34% (−17%, −55%)	10.3 (8.1, 13.2)	5.5 (4.6, 6.7)	0.0001	—