Drugs in Pregnancy and Lactation: Tenth Edition

CASTOR OIL

Laxative/Oxytocic

PREGNANCY RECOMMENDATION: Human Data Suggest Risk

BREASTFEEDING RECOMMENDATION: No Human Data—Potential Toxicity

PREGNANCY SUMMARY

Castor oil has been used since ancient times to induce labor. Nevertheless, neither the efficacy for this indication nor the fetal/newborn safety has been documented. One study found that the drug had no value to labor induction (1). Castor oil can cause severe maternal morbidity and possibly mortality, but this toxicity appears to be rare. However, maternal nausea and diarrhea appear to be very common, although underreported. The mechanism of castor oil’s oxytocic effect is unknown, but might be due to systemically absorbed ricinoleic acid stimulating uterine contractions. In recent times, the use of castor oil as an oxytocic agent has declined, probably because of the availability of safer and more physiologic agents, such as oxytocin and the two prostaglandins: dinoprostone and misoprostol. Although the report of multiple congenital defects attributed to castor beans early in gestation requires confirmation, castor beans should be avoided in pregnancy. As for castor oil, the limited human data offer no documented benefits for the mother or fetus. Uterine bleeding and abortion are potential toxicities. Thus, the use of castor oil as a laxative or for other purposes before term pregnancy should be avoided. Use at term should only be on the advice of a healthcare provider.

FETAL RISK SUMMARY

Castor, Ricinus communis, is an ornamental plant native to the West Indies, but now grows in the United States and Hawaii (2). Castor oil is cold expressed from castor beans (i.e., seeds) and contains a mixture of triglycerides. The principal compound is ricinoleic acid with smaller amounts of linoleic, oleic, pamitic, and stearic acids. The oil also contains toxins, such as ricin and ricinine, that are removed with further processing (2). Upon ingestion, castor oil is hydrolyzed in the duodenum by pancreatic lipase to release glycerol and the active ingredient, ricinoleic acid (3,4). Castor seeds contain ricin and can cause poisoning (3). Castor oil has been used for the induction of labor, and as a cathartic, contraceptive cream, lubricant, and skin emollient (2,3). It also has been combined with quinine to induce labor at term and topically as a contraceptive and abortifacient (3).

A 1983 report described an infant with growth restriction, convulsions, craniofacial dysmorphia, absent deformity of limbs, and vertebral segmentation defect that was born from a 20-year-old mother (5). The mother had taken a castor oilseed, once per month, as a contraceptive for 3 months before conception and during the first 2 months of gestation. No other drugs were taken during pregnancy. Because ricin is a potent toxin, the authors attributed the defects to the castor oilseeds (4). Of interest, a 2002 review stated (without specific reference) that castor bean had emmenagogue and abortifacient effects (6).

Castor oil has been used since ancient Egypt to induce labor (1,2,715). A 1958 study evaluated the efficacy of castor oil for the induction of labor (1). In the first part of the study, the investigator polled obstetric department heads of 50 medical schools. Of the 32 who responded, 16 never used castor oil for labor induction, whereas 16 used it some times. A retrospective review of 114 consecutive inductions (1952–1954) was conducted at the investigator’s institution. All of the inductions involved rupture of membranes and oxytocin. The group was divided into four subgroups: rupture of membranes and oxytocin (N= 24), added enema (N = 27), added castor oil (N = 31), and added castor oil and enema (N = 32). The average induction times for the four groups were 4, 2, 4, and 4 hours, respectively. The 18 induction failures were nearly equal in the groups: 5, 5, 3, and 5, respectively. These results convinced the investigator that castor oil had no value in the induction of labor (1).

The uterine activity effect of castor oil, soap enema, hot bath, or a combination of all three was described in 60 women at 38–41 weeks’ gestation in a 1959 study (7). Castor oil plus soap enema had the most marked effect, but most of the increased activity was due to castor oil. A hot bath had little effect. The effects on delivery times, induction failure, and pregnancy outcomes were not provided. Nevertheless, based solely on uterine activity, the investigators concluded that labor induction with castor oil, with or without soap enema, was useful (7).

A 1999 survey found that among 90 nurse-midwives who used herbal products for labor induction, castor oil (93%) was most the common (8). The doses used ranged from 5 to 120 mL. The mechanism of the oxytocic effect is unknown, but various authors have stated that it is secondary to intestinal peristalsis or an increase in the concentrations of prostaglandin E (9,10,12). However, a brief 2002 report stated that the oxytocic effect was due to systemically absorbed ricinoleic acid that caused contractions of the uterine musculature (13). Nausea is a very common adverse effect, as is diarrhea after delivery. The use of castor oil does not appear to directly affect the fetus or the Apgar scores at birth, but most reports fail to mention the condition of the newborn. Two reviews concluded that there is insufficient evidence to support the use of castor oil as an induction agent (14,15).

A 1987 study reported an increase in meconium staining of the amniotic fluid in women given castor oil for labor induction compared with controls (16). Meconium staining occurred in 4 (2.3%) of 174 women given castor oil compared with 0 of the 304 controls (p <0.1). Although the authors deemed the result significant, the difference might not have been if the standard pvalue of <0.05 has been used. In another report, 10.4% of women receiving castor oil had meconium-stained amniotic fluid compared with 11.5% of controls (ns) (12).

A case report describing amniotic fluid embolism associated temporally with castor oil was published in 1988 (17). A 33-year-old woman at 40 weeks’ gestation with an uncomplicated pregnancy and unremarkable medical history ingested 30 mL castor oil for labor induction. About 60 minutes later, spontaneous rupture of membranes occurred, followed by cardiorespiratory arrest. A dead fetus, with no observable abnormalities, was delivered, along with a normal placenta, in the intensive care unit. Maternal blood contained fetal squamous cells and amniotic fluid debris. The clinical course was complicated by seizures and findings consistent with disseminated intravascular coagulation. EEG findings were consistent with anoxic encephalopathy. At the time of the report, the woman remained in a persistent vegetative state (17).

A 2003 case report described uterine rupture in a 39-year-old woman at 39 weeks’ gestation (18). The woman experienced a brief bowel movement, followed by severe abdominal pain and rupture of membranes shortly after ingesting castor oil 5 mL for labor induction. A repeat cesarean section, performed for fetal distress and a closed, long cervix, revealed a portion of the umbilical cord protruding from a 2-cm rupture of the lower transverse scar. A female 2724-g female infant was delivered with Apgar scores of 9 at 1 and 5 minutes (18).

An unusual use of castor oil in pregnancy was briefly reported in 1967 (19). Castor oil was applied to the cervical os to facilitate vaginal delivery. The author noted that the use of oil to lubricate the vagina and os during labor was common among midwives in his region.

BREASTFEEDING SUMMARY

No reports describing the use of castor oil during lactation have been located. Castor oil has been used orally to promote the flow of breast milk (2). Evidence for this effect has not been located. The principal active ingredient, ricinoleic acid, is absorbed systemically and could be excreted into milk. Diarrhea in the nursing infant is a potential complication. In a rural region of India, newborn infants are sometimes given castor oil for its laxative properties in the belief that it will clean the intestine of meconium (20). However, this practice has been discouraged because it can be dangerous for the infant, at times causing paralytic ileus and aspiration pneumonia (20).

References

1.Nabors GG. Castor oil as an adjunct to induction of labor: critical re-evaluation. Am J Obstet Gynecol 1958;75:36–8.

2.Castor. The Review of Natural Products. Facts and Comparisons. St. Louis, MO: Wolters Kluwer Health, 2007.

3.Castor Oil. Castor Seed. Natural Medicines Comprehensive Database. 5th ed. Stockton, CA: Therapeutic Research Faculty, 2003:296–7, 298–9.

4.Gattuso JM, Kamm MA. Adverse effects of drugs used in the management of constipation and diarrhoea. Drug Saf 1994;10:47–65.

5.Mauhoub ME, Khalifa MM, Jaswal OB, Garrah MS. “Ricin syndrome.” A possible new teratogenic syndrome associated with ingestion of castor oil seed in early pregnancy: a case report. Ann Trop Paediatr 1983;3:57–61.

6.Ernst E. Herbal medicinal products during pregnancy: are they safe? Br J Obstet Gynaecol 2002;109:227–35.

7.Mathie JG, Dawson BH. Effect of castor oil, soap enema, and hot bath on the pregnant human uterus near term: a tocographic study. Br Med J 1959;1:1162–5.

8.McFarlin BL, Gibson MH, O’Rear J, Harman P. A national survey of herbal preparation use by nurse-midwives for labor stimulation. J Nurse-Midwifery 1999;44:205–16.

9.Davis L. The use of castor oil to stimulate labor in patients with premature rupture of membranes. J Nurse Midwifery 1984;29:366–70.

10.Harris M, Nye M. Self-administration of castor oil. Mod Midwife 1994;4:29–30.

11.Summers L. Methods of cervical ripening and labor induction. J Nurse Midwifery 1997;42:71–85.

12.Garry D, Figueroa R, Guillaume J, Cucco V. Use of castor oil in pregnancies at term. Altern Ther Health Med 2000;6:77–9.

13.Lippert TH, Mueck AO. Labour induction with alternative drugs? J Obstet Gynaecol 2002;22:343.

14.Kelly AJ, Kavanagh J, Thomas J. Castor oil, bath and/or enema for cervical priming and induction of labour. Cochrane Database Syst Rev 2002;(2):Art. No: CD003099. doi:10.1002/14651858.CD003099.

15.Tenore JL. Methods for cervical ripening and induction of labor. Am Fam Physician 2003;67:2123–8.

16.Mitri F, Hofmeyr GJ, Van Gelderen CJ. Meconium during labor—self-medication and other associations. S Afr Med J 1987;71:431–3.

17.Steingrub JS, Lopez T, Teres D, Steingart R. Amniotic fluid embolism associated with castor oil ingestion. Crit Care Med 1988;16:642–3.

18.Sicuranza GB, Figueroa R. Uterine rupture associated with castor oil ingestion. J Matern Fetal Neonatal Med 2003;13:133–4.

19.Tendulkar S. Local lubrication in labour. Indian Med J 1967;61:176.

20.Benakappa DG, Shivananda MR, Benakappa AD. Breast-feeding practices in rural Karnataka (India) with special reference to lactation failure. Acta Peadiatr Jpn 1989;31:391–8.