Authors (including presenting author) :
Kong SY (1), Chan KP (1), Li CH (1), Wong KW (1), Li KSJ (1), Chan HN (1), Chan PC (1), Chow PY (1), Fu HC (1), Mak CL (1), Mak HS (1), Ng SS (1), Tung KK (1), Lo ML (1), Wong YC (1). Tse PLK (2), Young WMG (2), Ha CY (1), Lai HK (1), Yip SF (1), Yeung YM (1)
Affiliation :
(1) Division of Haematology and Haematological Oncology, Department of Medicine and Geriatrics, Tuen Mun Hospital (2) Department of Pharmacy, Tuen Mun Hospital
Introduction :
High dose methotrexate (HD MTX) is one of the chemotherapeutic agents with specific antidote, leucovorin, also known as folinic acid. However, HD MTX often leads to renal toxicity which may delay chemotherapy and prolong hospitalization. The nephrotoxicity can be alleviated by urine alkalization. Also, the narrow therapeutic window of HD MTX necessitates drug level monitoring and antidote adjustment but logistic limitation creates clinical challenges.
Objectives :
1) To reduce renal complication through protocol standardization and prescription simplification and 2) To minimize delivery delay of blood samples for MTX level and allow timely antidote adjustment
Methodology :
Our project was conducted from August 2018 to November 2018.
Phase 1 - Problem identification in current practice:
1. Confusing antidote terminology (Leucovorin vs. Folinic acid)
2. Variable antidote routes of administration (Intravenous vs. Oral)
3. Different prescription criteria of sodium bicarbonate (NaHCO3) tablets
4. Late arrival of blood samples for MTX level to laboratory
Phase 2 - Amendment and Implementation:
1. Education on pharmacology, clinical use and toxicity
2. Protocol revision: A) Only “Leucovorin” was used to align with dispensing labels, B) Leucovorin was standardized to intravenous administration, C) NaHCO3 tablets were mandatory and D) Incorporation of intravenous fluid (IVF) and NaHCO3 tablets into the pre-printed medication administration record
3. Collaboration with other parties to supply HD MTX one day in advance, to aim at arrival of blood samples to laboratory by 4:30 p.m. and to minimize need of MTX level monitoring on Sunday or public holiday (PH)
Patients treated with pre-revised protocols from October 2017 to November 2018 (Pre-revised group) and those with revised protocols from December 2018 to June 2019 (Revised group) were recruited.
Result & Outcome :
There were 19 patients (48 admissions for chemotherapy, 152 total blood samples and 138 blood samples from Monday to Saturday except PH) and 10 patients (20 admissions, 63 total blood samples and 59 blood samples from Monday to Saturday except PH) recruited for Pre-revised and Revised group respectively. Nine (19%) episodes of renal derangement were reported from Pre-revised group while no (0%) renal complication was observed in Revised group (RRR = 100%, p = 0.037). In Pre-revised group, 43/138 (31%) blood samples arrived after 4:30 p.m. compared with 8/59 (14%) blood samples in Revised group (RRR= 54.8%, p = 0.01). 14/152 (9%) of MTX level monitoring was on Sunday or PH in Pre-revised group while 4/63 (6%) in Revised group (RRR = 33.3%, p = 0.49).
