Frågedatum: 1989-03-06
RELIS database 1989; id.nr. 6288, DRUGLINE
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Is methylene blue absorbed when given orally and rectally? What are its adverse effects?/nBackgroun



Fråga: Is methylene blue absorbed when given orally and rectally? What are its adverse effects? Background: A patient with intestinal inflammatory disease and recto-vaginal fistula will receive methylene blue orally and eventually as enema.

Sammanfattning: Methylene blue can be absorbed when administered orally (to an average of 74 per cent)

and rectally. Side effects reported after oral administration are mild. No side effects have been

reported with rectal administration.

Svar: Methylene blue is completely ionized in the upper gastrointestinal tract and well absorbed

in man. An average of 74 per cent (range 53 to 97 per cent) of an oral dose of 10 mg of

methylene blue can be recovered in the urine in a 120 hours interval as leucomethylene blue

and methylene blue (1). Absorption by the rectal mucosa has also been reported with a 100 ml

enema of 50 mg of methylene blue, confirmed by the urinary excretion of leucomethylene

blue and methylene blue as early as 30 minutes after its administration. Plasma levels of

methylene blue and leucomethylene blue were monitored in one patient with high urinary

levels and low levels of 1.80 mcg/ml of methylene blue plus 0.60 mcg/ml were observed 6

hours after the enema (2).

Rectovaginal fistula could probably be detected by the rectal injection of a solution of

methylene blue in saline and a cotton tampon placed in the vagina (3). Methylene blue 0.5 per

cent solution is used for the delineation of body structures and fistulas (4) but dilutions as low

as 0.001 per cent have been recommended for use during diagnostic laparoscopy (5).

Oral administration of methylene blue may cause nausea, vomiting, diarrhea and dysuria (4).

No side effects had been reported with rectal administration of methylene blue, despite

absorption. A low concentration of methylene blue in blood will convert methaemoglobin to

haemoglobin by a catalytic action on methaemoglobin reductase (1 to 4 mg/kg body weight as

a one per cent solution intravenously). In higher concentrations (5 mg/kg body weight

intravenously) the reverse occurs (4,6,7).

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