6.2 Distribution by route of exposure
Ethambutol diffuses readily into red blood cells and
into the cerebrospinal fluid when the meninges are inflamed.
The concentration in erythrocytes at steady state is
approximately twice the plasma concentration.
Protein binding is less than 5%; the volume of distribution
is 1.6 L/kg (Gilman et al., 1990)
It has been reported to cross the placenta and is excreted in
breast milk (Reynolds, 1989). The concentration of
ethambutol in one sample of breast milk collected during a 2
hour period after a dose of 15 mg per kg body-weight was 1.4
mcg/mL. Another woman had simultaneous concentrations of 4.62
and 4.60 œg/mL in plasma and milk respectively, but no dose
had been specified (Reynolds, 1989).