Table 2.

M : P values, average concentrations in milk, absolute infant doses and relative infant doses for rac-tramadol and rac-O-desmethyltramadol calculated from the steady-state data^*

Parameter	Number of: patients/data points	rac-Tramadol	rac-O-Desmethyltramadol
M : P	73/73	2.2 (2.0, 2.4)	2.8 (2.5, 3.1)
Milk Cavg (μg l−1)	55/165	748 (681, 815)	203 (188, 217)
Absolute infant dose (μg kg−1 day−1)	55/165	112 (102, 122)	30 (28, 32)
Relative infant dose	55/165 (%)†	2.24 (2.04, 2.44)	0.64 (0.59, 0.69)‡

^*mean (95% CI),

^†assuming 100 mg tramadol HCl administered 6 hourly to a 70 kg mother (5020 μg kg ⁻¹day⁻¹ as tramadol base),

^‡as tramadol molar equivalents. M : P, milk to plasma ratio.