A1,
A2,
B,
C1,
C2,
D,
E,
F,
G-H,
I-K,
L,
M,
N,
O,
P1,
P2,
Q-R,
S,
T,
U-V,
W-Z
Purinethol Side Effects, and Drug Interactions - Mercaptopurine
Purinethol Side Effects, and Drug Interactions - Mercaptopurine
SIDE EFFECTS
The principal and potentially serious toxic effects of PURINETHOL are bone
marrow toxicity and hepatotoxicity (see WARNINGS ).
Hematologic: The most frequent adverse reaction to PURINETHOL
is myelosuppression. The induction of complete remission of acute lymphatic
leukemia frequently is associated with marrow hypoplasia. Maintenance of remission
generally involves multiple-drug regimens whose component agents cause myelosuppression.
Anemia, leukopenia, and thrombocytopenia are frequently observed. Dosages and
schedules are adjusted to prevent life-threatening cytopenias.
Renal: Hyperuricemia may occur in patients receiving PURINETHOL
as a consequence of rapid cell lysis accompanying the antineoplastic effect.
Adverse effects can be minimized by increased hydration, urine alkalinization,
and the prophylactic administration of a xanthine oxidase inhibitor such as
allopurinol. The dosage of PURINETHOL should be reduced to one third to one
quarter of the usual dose if allopurinol is given concurrently.
Gastrointestinal: Intestinal ulceration has been reported.
20 Nausea, vomiting, and anorexia are uncommon during initial administration.
Mild diarrhea and sprue-like symptoms have been noted occasionally, but it is
difficult at present to attribute these to the medication. Oral lesions are
rarely seen, and when they occur they resemble thrush rather than antifolic
ulcerations.
An increased risk of pancreatitis may be associated with the investigational
use of PURINETHOL in inflammatory bowel disease. 21 - 23
Miscellaneous: While dermatologic reactions can occur as
a consequence of disease, the administration of PURINETHOL has been associated
with skin rashes and hyperpigmentation. 24
Drug fever has been very rarely reported with PURINETHOL. Before attributing
fever to PURINETHOL, every attempt should be made to exclude more common causes
of pyrexia, such as sepsis, in patients with acute leukemia.
DRUG INTERACTIONS
Interaction with Allopurinol: When
allopurinol and mercaptopurine are administered concomitantly, it is imperative
that the dose of mercaptopurine be reduced to one third to one quarter of the
usual dose. Failure to observe this dosage reduction will result in a delayed
catabolism of mercaptopurine and the strong likelihood of inducing severe toxicity.
There is usually complete cross-resistance between mercaptopurine and thioguanine.
The dosage of mercaptopurine may need to be reduced when this agent is combined
with other drugs whose primary or secondary toxicity is myelosuppression. Enhanced
marrow suppression has been noted in some patients also receiving trimethoprim-sulfamethoxazole.
17,18
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