Permeability of the blood-milk barrier to methylene blue in cows and goats

J Vet Pharmacol Ther. 1984 Mar;7(1):55-9. doi: 10.1111/j.1365-2885.1984.tb00879.x.


A 2% aqueous solution of methylene blue was administered as a single intravenous (i.v.) bolus injection (10 mg/kg) to six lactating cows and seven lactating goats and a continuous i.v. drip to five lactating goats. The same dose was administered as a 10% solution by intramammary infusion to five lactating goats. Blood and milk samples collected at various times after these treatments were assayed for the drug by a colorimetric method. Methylene blue, a highly charged molecule (pKa less than or equal to 1), passed readily from blood into milk; drug concentrations in milk 4-36 h after the single i.v. bolus injection were higher than those in blood. When examined at constant methylene blue levels in blood, a milk--blood ratio of 5:1 was observed. After intramammary infusion, the drug passed quickly into systemic circulation, peaked at 3 h and was still detectable in blood 12 h after infusion. The drug appeared in the urine within 15 min after intramammary infusion. The rapid movement of the drug across the blood--milk barrier cannot be explained on the basis of its known physicochemical properties or according to the pH--pKa passive diffusion concept.

MeSH terms

  • Animals
  • Capillary Permeability*
  • Cattle / metabolism*
  • Female
  • Goats / metabolism*
  • Injections, Intravenous / veterinary
  • Lactation
  • Male
  • Methylene Blue / administration & dosage
  • Methylene Blue / blood
  • Methylene Blue / metabolism*
  • Milk / metabolism*
  • Pregnancy
  • Time Factors


  • Methylene Blue