Therapeutic Interventions For Pain Induced By Vincristine Treatment For Childhood Acute Lymphoblastic Leukemia (ALL)

Patients with ALL on Total XVI ((or for those being treated "as per TOTXVI protocol") who experience NP/PN after specific doses of vincristine are eligible to enroll in the study as soon as the diagnosis of NP/PN related to VCR is established. The qualifying doses of vincristine have been selected because they fall in the schedule of weekly vincristine doses as per Total XVI, and 2 additional weekly vincristine doses are anticipated according to the protocol. Participants will be randomized to receive gabapentin or placebo upon enrollment. Morphine will be available to both groups as needed for pain at any time on the study. At the time of enrollment, and daily thereafter until completion of the study drug, data will be collected for pain assessment, and the daily dose of oral morphine used will be collected. Data regarding the pain type, quality, and location, as well as treatments used to manage pain will be assessed on a daily basis for the diagnostic event and for the period following the next two administrations of VCR treated with the study drug.

Primary Objective: To assess the analgesic efficacy of gabapentin in controlling VCR-related NP/PN in participants with ALL, by comparing the morphine daily dose (mg/kg/day) used to control NP/PN as a primary or a rescue regimen in the gabapentin vs. placebo groups.

Secondary Objective: To compare the pain scores in the gabapentin and placebo groups as recorded by pain score right now and pain score average for previous 24 hours.

Inclusion criteria

• Participant is enrolled on Total XVI or who are being treated "as per TOTXVI protocol"
• Participant is 1 year of age or older
• Participant has symptoms of NP/PN with onset no more than 7 days after one of the following vincristine doses ± 3 days: protocol week 1, week 2 (induction), week 7 (reinduction I), or week 17 (reinduction II).
• Patient is expected to receive 2 doses of vincristine in weekly intervals as outlined by the Total XVI protocol (or for those being treated "as per TOTXVI" protocol) while on study drug (i.e. no known dosage reductions or planned missed doses).

Participant is able and willing to take oral medications.

Exclusion criteria

• Previous participation in this study
• Participant is receiving gabapentin for another indication at the time of diagnosis of NP/PN or has received gabapentin previously.
• Pregnancy. Female participants of childbearing potential must have documented negative urine or serum pregnancy test result not older than 7 days. Male patients with reproductive potential will be counseled not to procreate during the study.
• Impaired renal function: decreased eGFR (<60ml/min/1.73m^2 as estimated by the revised Schwartz equation)
• Participant has allergy or other contraindication for either morphine or gabapentin therapy.
• Inability or unwillingness of research participant or legal guardian/representative to give written informed consent.