Neutropenia due to low-dose methotrexate therapy for psoriasis and rheumatoid arthritis may be fatal.
OBJECTIVE
To review experience with neutropenia related to low-dose methotrexate therapy in patients with psoriasis and rheumatoid arthritis.


METHODS
Retrospective review of medical records.


METHODS
A 509-bed Melbourne teaching hospital.


METHODS
Five patients admitted in 1987 and 1988, with neutrophil counts of less than 1 x 10(9)/L, given low doses of methotrexate for psoriasis or rheumatoid arthritis.


METHODS
Death, or length of hospital admission.


RESULTS
Four patients were women, and one a man; three had been treated for psoriasis, and two for rheumatoid arthritis. Ages ranged from 56 to 91 years. The eldest patients, aged 77, 81 and 91 years, died. The other two were discharged after 43 and 48 days. Prior to or shortly after admission, four patients were treated with penicillin antibiotics which may have interfered with methotrexate excretion.


CONCLUSIONS
Methotrexate clearances (related to creatinine clearance rates and presumably low) were probably reduced sufficiently by concomitant therapy to result in neutropenia. Practitioners using methotrexate should be aware of drug interactions resulting in delayed methotrexate excretion. Blood counts should be monitored after changes in therapy, especially in patients with impaired renal function, such as the elderly.
Mayall
B
B
Repatriation General Hospital, Heidelberg, VIC.
Poggi
G
G
Parkin
J D
JD
D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000188:drug therapy*; D004347:Drug Interactions; D005260:Female; D006801:Humans; D008297:Male; D008727:Methotrexate / Q000008:administration & dosage / Q000009:adverse effects* / Q000378:metabolism; D008875:Middle Aged; D009503:Neutropenia / Q000139:chemically induced*; D010406:Penicillins / Q000627:therapeutic use; D011565:Psoriasis / Q000188:drug therapy*; D012189:Retrospective Studies
D010406:Penicillins; D008727:Methotrexate