Therapy with methylene blue may significantly shorten the period of time that a patient with methemoglobinemia is exposed to toxic levels of methemoglobin.
If left untreated the half-life of methemoglobin is 15 to 20 hours.
If optimally treated with methylene blue the half life is 0.66 to 1.5 hours (40 to 90 minutes).
Using the equation for second order kinetics:
concentration at given time =
= (initial concentration) * EXP((-1) * k * (number of hours))
Half-Life
k for Half-Life
20 hours
0.035
15 hours
0.046
1.5 hours
0.46
0.66 hours
1.05
Assumptions:
(1) There is no more production of methemoglobin.
(2) Methylene blue is not given in toxic doses sufficient to cause methemoglobinemia.
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