New Drug Information by Thomas W. Hale, PhD

Tobramycin:
In a recent case report of a woman receiving tobramycin for an infection, levels in milk were undetectable (0.18 mg/L). Plasma levels in the patient, who received 150 mg three times daily, were reported to be 0.4 mg/L prior to infusion and 12.5 mg/L 30 minutes after infusion.1

Quetiapine:
In a study of 6 women consuming quetiapine while breastfeeding, levels in breastmilk were studied along with the neurobehavioral outcomes (Bayley Scales) in their infants.2 In 3 of the 6 cases, quetiapine was not detected in breast milk. In all but one case, the estimated dose of medications was calculated to be < 0.01 mg/kg/day.

In 3 of the 6 cases, no medication was detected in the breast milk (< 30 nmol/L). Four of the 6 babies scored as being within normal limits on the Bayley Scales of Infant Development, whereas 2 showed mild developmental delays. Infants with mild delay did not have higher levels of psychotropic medication exposure and the authors suggest no association was evident between developmental outcomes and exposure through breast milk to quetiapine and other medications present.

Dexamphetamine:
In a group of four women who received 15-45 mg/day of dexamphetamine, milk/plasma ratios were high (3.3), the absolute infant dose/day was 21 ug/kg/day, while the median calculated relative infant dose was only 5.7% (range 3.9 to 13.8%) of the weight-adjusted maternal dose.3 No adverse effects were noted in the infants; although, the authors suggest that at the higher reported levels, some CNS stimulation could occur in some infants. Mothers and infants should be monitored closely for both maternal dose and side effects in the infants exposed via breastfeeding.

Neonatal Abstinence and Breastfeeding:
This is an interesting study as it is the first I know of that suggests that neonatal abstinence syndrome is reduced by breastfeeding. The authors in this study conducted a retrospective chart review of 190 drug-dependent mother and infant pairs.4 Infant withdrawal was evaluated by Finnegan scoring. In this group, mean Finnegan scores were significantly lower in the breastfed group during the first 9 days postpartum. Fewer infants required withdrawal treatment if they were breastfed. The median time to withdrawal occurred considerably later in breast milk group. The authors concluded that breast milk intake was associated with reduced neonatal abstinence severity, delayed onset of neonatal abstinence syndrome, and reduced need for treatment.

Reference List
(1) Festini F, Ciuti R, Taccetti G, Repetto T, Campana S, De MM. Breast-feeding in a woman with cystic fibrosis undergoing antibiotic intravenous treatment. J Matern Fetal Neonatal Med 2006 June;19(6):375-6.
(2) Misri S, Corral M, Wardrop AA, Kendrick K. Quetiapine augmentation in lactation: a series of case reports. J Clin Psychopharmacol 2006 October;26(5):508-11.
(3) Ilett KF, Hackett LP, Kristensen JH, Kohan R. Transfer of dexamphetamine into breasat milk during treatment for attention deficite hyperactivity disorder. Br.J.Clin.Pharmacol. doi:10.1111/j.1365-2125.2006.02767.x. 2006.
Ref Type: Journal (Full)
4) Abdel-Latif ME, Pinner J, Clews S, Cooke F, Lui K, Oei J. Effects of breast milk on the severity and outcome of neonatal abstinence syndrome among infants of drug-dependent mothers. Pediatrics 2006 June;117(6):e1163-e1169.