Table 2.

Enantiomer-Specific Methadone Concentrations (mg/L) in Breastmilk and Maternal Plasma

			Breastmilk				Maternal plasma
Sample	Dose (mg/day)	Peak or trough	R-Methadone	S-Methadone	Total methadone	R/S-Methadone	R-Methadone	S-Methadone	Total methadone	R/S-Methadone
1	40	Peak	0.0606	0.0413	0.1019	1.47	0.1220	0.150	0.272	0.81
2	50	Peak	0.0302	0.0174	0.0476	1.74	0.0876	0.0974	0.185	0.89
3	60	Peak	0.0866	0.0549	0.1415	1.58	0.1840	0.274	0.458	0.67
4	60	Peak	0.0720	0.0340	0.1060	2.12	0.0938	0.102	0.1958	0.92
5	70	Peak	0.0252	0.0146	0.0398	1.73	0.4720	0.644	1.116	0.73
6	75	Trough	0.0367	0.0119	0.0486	3.08	0.0787	0.0363	0.115	2.17
7	75	Peak	0.0714	0.0529	0.1243	1.35	0.1630	0.198	0.361	0.82
8	77	Peak	0.1430	0.0970	0.2400	1.47	0.2700	0.343	0.613	0.79
9	80	Trough	0.0617	0.0328	0.0945	1.88	0.1660	0.170	0.336	0.98
10	90	Trough	0.0342	0.0152	0.0494	2.25	0.1890	0.160	0.349	1.18
11	90	Peak	0.0661	0.0438	0.1099	1.51	0.256	0.284	0.540	0.90
12	100	Peak	0.2210	0.0998	0.3208	2.21	0.1740	0.1470	0.321	1.18
13	100	Peak	0.1080	0.0668	0.1748	1.61	0.2530	0.2740	0.527	0.92
14	110	Peak	0.1830	0.1160	0.2990	1.58	0.2790	0.2710	0.550	1.03
15	115	Peak	0.6590	0.4710	1.1300	1.40	0.7200	1.0450	1.765	0.69
16	123	Trough	0.0670	0.0310	0.0980	2.16	0.1740	0.1650	0.339	1.05
17	170	Peak	0.1700	0.0995	0.2695	1.71	0.1880	0.1980	0.386	0.95
18	177	Peak	0.0970	0.0381	0.1351	2.55	0.2480	0.1770	0.425	1.40
19	180	Peak	0.1670	0.0826	0.2496	2.02	0.4420	0.3590	0.801	1.23
20	200	Peak	0.3590	0.2530	0.6120	1.42	0.5480	0.6410	1.189	0.85
Mean	102.1	—	0.1359	0.0837	0.2196	1.84	0.2554	0.2868	0.5422	1.01
SD	46.2	—	0.1473	0.1063	0.2531	0.45	0.1672	0.2384	0.4017	0.33
Range	40–200	—	0.025–0.659	0.012–0.471	0.040–1.13	1.35–3.08	0.079–0.720	0.036–1.045	0.115–1.765	0.67–2.17

Peak indicates that the sample was obtained between 2 to 4 hours after the mother took her daily methadone dose. Trough indicates that the sample was obtained at least 20 hours after the mother took her last methadone dose.