Individualized misoprostol dosing for labor induction or augmentation: A review

Table 1 Comparison of titrated oral misoprostol in labor induction between studies

Ref.	Year	No. of women	Initial dosage (μg)	Dosing interval	Efficacy	Adverse effects	Cesarean rate (%)
Hofmeyr et al[18]	2001	25	20	q2h	72% VD within 32 h	8% UH	20.0
Hofmeyr et al[19]	2001	346	20	q2h	62% VD within 24 h	4% UH	16.0
Matonhodze et al[24]	2003	176	20	q2h	60.2% VD within 24 h	4% UH, 8% UT	14.0
Cheng et al[20]	2006	77	20	q1h	93.5% VD within 24 h	0% UH, 9.1% UT	3.9
Bricker et al[25]	2008	375	20	q2h	76% VD within 24 h	2% UH, 5% UT	14.0
Cheng et al[21]	2008	101	20	q1h	94.1% VD within 24 h	0% UH, 6.9% UT	4.0
Ho et al[22]	2010	112	20	q1h	94.6% VD within 24 h	0% UH, 7.1% UT	3.6
Souza et al[23]	2010	30	20	q1h	80% VD within 24 h	13.3% UT	20.0

VD: Vaginal delivery; UH: Uterine hyperstimulation; UT: Uterine tachysystole.

Table 2 Mathematical model of titrated oral misoprostol

	Times t = 34 + 60n, n = 0, 1, 2, 3, --- (min)
Dosage (mcg)	34	94	154	214	274
20	P
20		P(1/40 + 1/41)
20			P(1/40 + 1/41 + 1/42)
20				P(1/40 + 1/41 + 1/42 + 1/43)
40					P + P(1/40 + 1/41 + 1/42 + 1/43 + 1/44)
…

Set the function C = f(t), where C: Concentration of misoprostol acid (pg/mL) in plasma; t: Times during the whole process, t = 34 + 60n (min), when taking misoprostol at n = 0, 1, 2, 3, --- (h); T_max (the time to peak plasma concentration of misoprostol acid after absorption): 34 min; T_1/2 (the half-life of misoprostol acid): 30 min as determined by a pharmacokinetics study. When n = 0, intake 20 µg, t = 34 min, set the peak plasma concentration of misoprostol acid, C = P; When n = 1, intake 20 µg, t = 34 + (60 × 1) = 94 min, and C = P(1/4⁰ + 1/4¹); When n = 2, intake 20 µg, t = 34 + (60 × 2) = 154 min, and C = P(1/4⁰ + 1/4¹ + 1/4²); When n = 3, intake 20 µg, t = 34 + (60 × 3) = 214 min, and C = P(1/4⁰ + 1/4¹ + 1/4² + 1/4³); When n = 4, intake 40 µg, t = 34 + (60 × 3) = 214 min, and C = P + P(1/4⁰ + 1/4¹ + 1/4² + 1/4³ + 1/4⁴) and so on. Therefore, C = f(t) is a convergent series in which the upper limit = P/(1 - 1/4) + P/(1 - 1/4) + --- = (4/3)P + (4/3)P + ---.