Active transport of nitrofurantoin across a mouse mammary epithelial monolayer.

The antibiotic nitrofurantoin is transported against an electrochemical gradient into milk. A monolayer of CIT3 cells, a subline of the Comma 1D normal mouse mammary epithelial cell line, transports [14C]-nitrofurantoin against a concentration gradient from the basal to the apical solution when grown on membrane filters. In a side-by-side diffusion chamber with well-stirred solutions on both sides, the transfer rate is 50% higher in the basal-to-apical than in the apical-to-basal direction. Nonlabeled nitrofurantoin (500 microM) in the basal chamber equalized the transport in both directions, suggesting that a specific transporter is responsible for the basal-to-apical increment in flux. From inhibition studies, the apparent affinity of this transporter for nitrofurantoin is 50 microM. Changes in pH between 6.4 and 7.8 had no effect on the active transport component of the flux but did affect the passive flux component. Passive flux of the nonionized molecule was 2.6 times faster than that of the ionized molecule, but the ionized molecule did appear to cross the membrane passively. Our findings show that nitrofurantoin is actively transported across a mammary epithelial cell monolayer by a transporter whose affinity for nitrofurantoin does not depend on the anionic charge on nitrofurantoin. The pH dependence of a parallel passive pathway suggests that both nonionized and ionized forms of nitrofurantoin cross the membranes of the mammary epithelial cell by passive diffusion.

Low-dose progestogen contraception and the nursing mother.

Breast feeding, though an important and efficient contraceptive method, suffers from one major limitation: the contraceptive protection it offers the nursing mother ends abruptly without giving any physical indication of the return of fertility. Barrier methods and progesterone-only hormonal contraceptives, either in the oral, implant or injectable form, appear to be the primary contraceptive alternative for the nursing mother today. They neither adversely affect lactation, nor does the minute quantity of progesterone (NET or LNG) transferred to the infant affect its growth and physical well-being. Puerperal insertion of IUD carries an inherent risk of pelvic inflammatory disease, high expulsion rates and menorrhagia, once menses resume. Combination contraceptives affect both the quality and quantity of breastmilk; hence they are not recommended. Sterilization is a permanent method and therefore useful only when the family has been completed.

Can chronic maternal drug therapy alter the nursing infant's hepatic drug metabolizing enzyme pattern?

This study was carried out to investigate whether minute quantities of maternal drugs ingested over an extended period of time by a breast-feeding infant can alter the activity pattern of the infant's hepatic drug metabolizing enzyme (HDME). The HDME activity patterns of 12 breast-fed infants whose mothers were not on drug therapy were compared with those of 11 infants whose mothers had been taking 30 micrograms levo-norgesterel daily for 90 to 195 days (oral contraceptives group) and of 10 infants whose mothers had been taking ethambutol and isoniazid daily since pregnancy (tuberculosis group). As 6 beta hydroxycortisol in urine is considered to be a good and acceptable reflector of HDME activity, it was estimated from the infants' urine using enzyme-linked immunosorbent assay (ELISA) technique. A comparison of the patterns between 90 days of age and 195 days of age of the infants in the control group and the two study groups indicated an increase from 36.6 ng/mL to 58.4 ng/mL at 195 days in the control group. An initial decrease from 36.6 ng/mL to 26.2 ng/mL was noted with commencement of maternal levo-norgesterel therapy, followed by a slow and steady rise to 47.8 ng/mL at 195 days of age, with a shift in the peak from 120 to 135 days of infants age in the oral contraceptive group. A suppressed pattern with decreased levels of 6 beta hydroxycortisol ranging from 19.3 ng/mL to 26.5 ng/mL at 195 days was found in the tuberculosis group. The data were analyzed by two-way analysis of variance (ANOVA) coupled with Duncan's Multiple range test. Both treatment group showed significant differences from the control group at the 0.050 level. The HDME plays an important role in determining the final outcome of any drug in humans, as it controls the metabolism of drugs. Hence, alterations in its activity caused by the transfer of maternal drugs over a prolonged period of time could pose a serious problem to nurslings when they require drugs for their own benefit.

Is time-interval between mini-pill ingestion and breastfeeding essential?

A study was conducted on four alternate days over an eight-day period in a group of 12 healthy, 20-35 year old exclusively breast feeding women who were interested in weaning their infants. On each study day the women ingested 150 micrograms levonorgestrel. Maternal blood and milk samples were collected at 2, 4, 6, and 8 hr intervals after LNG ingestion on the 1st, 3rd, 5th, and 8th day. A time-dependent decrease in maternal serum and increase in breast milk levels of LNG were observed. Maintaining a time interval between mini-pill intake and breastfeeding results in higher levels of LNG in breast milk, thereby exposing the infant to a bolus of LNG in a "single-delayed" feed.

PIP: In India over an 8-day period, 12 healthy, lactating women aged 20-35 (body mass index, 21-23) who took a mini-pill with 150 mcg levonorgestrel (LNG) (Microlut) daily provided blood and breast milk samples over increasing time intervals between LNG ingestion and sample-taking. The researchers wanted to determine whether a time interval between maternal LNG ingestion and breast feeding delivers less LNG to the breast milk and the infant. Regardless of the time interval, about 10% of the LNG in the blood was transferred to the breast milk. The observed LNG levels in the breast milk were higher than the expected LNG levels, except at a 2-hour interval. Maternal sera LNG levels decreased as the time intervals increased (1198 pg/ml at 2 hours, 995 at 4 hours, 476 at 6 hours, and 340 at 8 hours), while the LNG levels in breast milk increased (100, 180, 250, and 330 pg/ml, respectively). The researchers explained the decrease in maternal levels by metabolism of LNG by the mother's liver, but they could not account for the increase of LNG in the breast milk. These findings show that maintaining a time interval between maternal ingestion of LNG and breast feeding increases LNG in breast milk, exposing the infant to a bolus of LNG in one delayed feed.

At what 'infant-age' can levonorgestrel contraceptives be recommended to nursing mothers?

OBJECTIVE: Levonorgestrel (LNG), a low-dose progestin, does not affect lactation but like all drugs taken by breastfeeding mothers, it can be transferred to the infant via breast milk. How infants of various ages cope with this unwanted maternal drug would help in deciding when to recommend this method of contraception to breastfeeding mothers. METHODS: The study was conducted in 30 exclusively breastfeeding mothers and their 4-, 12- and 24-week-old infants. The mothers daily received 30 micrograms LNG over a five-week period, thus exposing their infants to maternal LNG for that period. RESULTS: Four-week-old infants could neither absorb nor metabolize LNG efficiently. Twelve-week-old infants could metabolize LNG more efficiently than absorb. Twenty-four-week-old infants could do both efficiently. CONCLUSION: It is safe to introduce LNG to breastfeeding mothers at 12 weeks postpartum.

A sensitive ELISA for 6 beta-hydroxycortisol in urine using enzyme penicillinase (beta-lactamase).

A sensitive and specific, enzyme labelled immunosorbent assay (ELISA) for 6 beta-hydroxycortisol in diluted urine using penicillinase was developed. 6 beta-Hydroxycortisol-21-hemisuccinate was conjugated with enzyme penicillinase. Antibody immobilized on a polyvinylchloride ELISA plate (Dynatech) was used for separation of bound from free ligand. The sensitivity of the assay was between 2.0-3.0 pg per well and recovery of 6 beta-hydroxycortisol from urine ranged between 85.0-108.0%. The assay is simple, rapid and precise.

ICMR Task Force Study on hormonal contraception. Transfer of norethisterone (NET) and levonorgestrel (LNG) from a single tablet into the infant's circulation through the mother's milk.

A single tablet of either of the three different types of oral contraceptive preparations, viz. "Gynovlar" containing 3000 micrograms norethisterone (NET) and 50 micrograms ethinyl estradiol (EE2) or "Ovral" containing 250 micrograms levonorgestrel (LNG) and 50 micrograms EE2, or a daily progestogen only type--"Minipill" containing 30 micrograms of LNG only, were administered to 40 normal lactating women on a random basis. The sampling schedule in all the three body fluids, i.e. the maternal sera, breast milk and the infant's sera, was kept in such a manner that the peak levels of the contraceptive steroids would be expected to be present in these fluids. The results of this study indicate that the transfer ratio of LNG or NET from the maternal sera to her breast milk was approximately 10% (6-34%) for Gynovlar, 9% (5-18%) for Ovral and 6% (2-34%) for Minipill. However, it was interesting to observe that whereas the transfer ratio of NET or LNG from breast milk to infant's sera was similar for combination pills--8% (3-23%) for Gynovlar and 12% (3-42%) for Ovral, it was significantly higher for progestogen only Minipills--38% (13-92%) for LNG. The precise reason for the higher transfer ratio of LNG from breast milk to infant's serum in Minipill users cannot be explained.

ICMR Task Force Study on hormonal contraception. Biological activity of ethinyl estradiol present in the breast milk.

A study was conducted to compare the biological activity of the estrogenic component of the endogenous steroids in breast milk samples collected during various phases of lactation with those milk samples collected from women who were on estrogen therapy. The estrogenic biological activity in the milk sample was assessed by the immature mouse uterine weight gain assay. Milk samples collected during postpartum period from six different study groups, viz., control colostrum of 1-3 days and 4-6 days, transitional milk (10-20 days) and mature milk (1-3 months) were compared with colostrum and mature milk of women treated with Lynoral (ethinyl estradiol 0.1 mg) three times a day for three days. Estrogenic activity was observed only in animals injected with milk extracts of colostrum samples from both control and Lynoral-treated women; however, they were not significantly different from each other. Therefore it is not the exogenous estrogens, but the endogenous estrogen present in large quantities in the colostrum that is responsible for the biological activity.

Reproductive endocrine effects of intranasal administration of norethisterone (NET) to women.

Four consecutive menstrual cycles were studied in six healthy parous women. A solvent mixture comprising propylene glycol:ethanol:water (3:3:4) was sprayed intranasally daily using a glass atomizer between days 5 and 24 of the first (control) menstrual cycle. NET was dissolved in the solvent and similarly administered at a daily dose of 100 mcg during the second and third menstrual cycles. Nasal sprays were not administered during the fourth post-treatment cycle. Blood samples were taken during four consecutive cycles between days 8 and 15 and again between days 20 and 24 of the cycle to estimate levels of estradiol (E2), FSH, LH and progesterone (P). These studies revealed that nasal sprays of NET were well accepted and that no adverse clinical effects or menstrual disturbances occurred. NET inhibited ovulation in one cycle. The E2-induced mid-cycle rise in FSH and LH was either suppressed or inhibited in nine out of the 12 treated cycles. P levels in three treated cycles were indicative of luteal inadequacy. These endocrine effects of NET persisted into the post-treatment cycle in two cases.

Release of 19-nor-testosterone type of contraceptive steroids through different drug delivery systems into serum and breast milk of lactating women.

The release of contraceptive steroids through different drug delivery systems into serum and breast milk was investigated in a group of lactating women. Four women in each group were taking either a low dosage progestogen compound like norethisterone (NET) 350 micrograms or d-norgestrel (d-Ng) 50 micrograms alone or low dosage combination pills containing NET 1 mg or d-Ng 150 micrograms with 30 micrograms ethinyl estradiol (EE2) or a biodegradable implant containing 25 mg NET or d-Ng. Peak levels in plasma and milk were seen in oral contraceptive users around 2 hours. Of the two low dosage progestogen compounds, d-Ng was below the detection limit in milk within 4 hours whereas NET was still detectable at the 24-hour interval. In contrast to this, because of the larger quantity of steroids in the combination pills, the NET/d-Ng levels in serum as well as in milk were high throughout the 24-hour period. With the subdermal route because of the sustained low release of the drug from the biodegradable implants, the levels in milk were below the detection limit within a day with d-Ng and within a week with NET.

PIP: Various drug delivery systems were tested and the release rates of steroids were measured in the serum and breast milk of a group of lactating women. 24 lactating women were divided into 3 groups: 1) low-dose combination (LDC) oral pill group; 2) low-dose progestin-only (LDP) oral pill group; and 3) biodegradable-cholesterol implants. Norethindrone (NET) or D-norgestrel (D-Ng) was the steroid released and it was assayed. LDC contained either 1 mg of NET or 150 mcg of D-Ng; LDP was 350 mcg of NET or 50 mcg of D-Ng; and the implants contained 25 mg of D-Ng or NET. By the oral route, peak levels of steroid were observed in both plasma and milk about 2 hours postdosing. In the LDP formulations, NET persisted within limits of detection for over 24 hours, whereas D-Ng was below the limit of detection in milk after 4 hours. In the LDC, however, detectable levels of both NET an D-Ng persisted for 24 hours. In the group implanted subcutaneously with progestin, levels of D-Ng were undetectable in milk within 1 day of insertion, and those of NET were undetectable within 1 week of implantation.

Effect of contraceptive steroids on human lactation.

Biochemical studies to detect changes occurring in the composition of mother's milk from the initiation of proper lactation to weaning were done in a group of 36 postpartum women, volunteers who were either using the conventional contraceptives or taking a low-dose combination pill, a low-dose progestational compound, or a 3 or 6 monthly injection as a mode of contraception. Apart from a significant increase in the protein content of milk and a slight increase in the quantity, the 3 monthly injection group behaved exactly like the control. On the other hand, the 6 monthly injection group showed a significant increase in quantity but with a significant decrease in protein, fats, and calcium. The low-dosage progestogens group showed a significant decrease in the quantity of fats and the calcium content of milk, but, surprisingly, the addition of 10 micrograms of estrogens to the low-dosage progestogen indicated a pattern almost similar to the control.