<p>The half life of low dose methotrexate is 3 to 10 hours in adults.<sup class="text-reference-group"><a class="reference-popover-link" data-content="FDA Approved Drug Products: Methotrexate Oral Solution" href="#reference-L7144">4</a></sup> The half life for high dose methotrexate is 8 to 15 hours.<sup class="text-reference-group"><a class="reference-popover-link" data-content="FDA Approved Drug Products: Methotrexate Subcutaneous Injection" href="#reference-L7147">5</a></sup> Pediatric patients taking methotrexate for acute lymphoblastic anemia experience a terminal half life of 0.7 to 5.8 hours.<sup class="text-reference-group"><a class="reference-popover-link" data-content="FDA Approved Drug Products: Methotrexate Oral Solution" href="#reference-L7144">4</a></sup> Pediatric patients taking methotrexate for juvenile idiopathic arthritis experience a half life of 0.9 to 2.3 hours.<sup class="text-reference-group"><a class="reference-popover-link" data-content="FDA Approved Drug Products: Methotrexate Oral Solution" href="#reference-L7144">4</a></sup></p>