I am following up on a patient who is a 3 mo male with ALL. The patient recieved induction?
Methotrexate therapy on June 23rd. The clearance trend is as follows:
June 24th 135.02 (umol/L)
June 25th early 7.26
June 25th late 3.52
June 27th 0.27
June 28th 0.45
June 29th early 0.65
June 29th late 0.59
June 30th 0.36
July 1st 0.1
July 2nd 0.03

There is a delayed clearance noted; however, I am hoping someone can help me to figure out the reason for the slight rise in Methotrexate level starting on the 28th. There was no more induction of therapy (this was stopped on the 23rd. There was no third spacing, no acitis, no pleural effusion, and liver functions were normal. What could cause a rise in Methotrexate levels after the drug had been cleared down to 0.45? Thank you for your help