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
Tapazole Warnings, Precautions, Pregnancy, Nursing, Abuse - Methimazole
Tapazole Warnings, Precautions, Pregnancy, Nursing, Abuse - Methimazole
WARNINGS
Agranulocytosis is potentially a serious side
effect. Patients should be instructed to report
to their physicians any symptoms of agranulocytosis, such as fever
or sore throat. Leukopenia,
thrombocytopenia,
and aplastic anemia (pancytopenia) may also occur. The drug
should be discontinued in the presence of agranulocytosis,
aplastic anemia (pancytopenia),
hepatitis, or exfoliative dermatitis. The patient’s bone
marrow function
should be monitored.
Due to the similar hepatic
toxicity profiles of
Tapazole and propylthiouracil, attention is drawn to the severe
hepatic reactions which
have occurred with both drugs. There have been rare reports of fulminant
hepatitis, hepatic
necrosis, encephalopathy,
and death. Symptoms suggestive
of hepatic dysfunction
(anorexia, pruritus,
right upper quadrant
pain, etc) should prompt
evaluation of liver function.
Drug treatment should
be discontinued promptly in the event of clinically significant
evidence of liver
abnormality including
hepatic transaminase
values exceeding 3 times the upper limit
of normal.
Tapazole can cause fetal
harm when administered to a pregnant
woman. Tapazole readily crosses the placental
membranes and can induce goiter and even cretinism
in the developing fetus. In
addition, rare instances of aplasia
cutis, as manifested by scalp
defects, have occurred in infants born to mothers who received Tapazole
during pregnancy. If Tapazole is used during pregnancy
or if the patient becomes
pregnant while taking
this drug, the patient
should be warned of the potential
hazard to the fetus.
Since scalp defects have
not been reported in offspring of patients treated with propylthiouracil,
that agent may be preferable
to Tapazole in pregnant
women requiring treatment
with antithyroid
drugs.
Postpartum patients receiving Tapazole should not nurse
their babies.
PRECAUTIONS
General
Patients who receive Tapazole should be under close surveillance
and should be cautioned to report
immediately any evidence
of illness, particularly sore throat,
skin eruptions, fever,
headache, or general
malaise. In such cases, white-bloodcell
and differential
counts should be made to determine whether agranulocytosis
has developed. Particular care should be exercised with patients
who are receiving additional drugs known to cause
agranulocytosis.
Laboratory Tests
Because Tapazole may cause
hypoprothrombinemia
and bleeding, prothrombin
time should be monitored during therapy
with the drug, especially
before surgical procedures (see Precautions: General, above). Periodic
monitoring of thyroid
function is warranted,
and the finding of an elevated TSH
warrants a decrease in the dosage
of Tapazole.
Carcinogenesis, Mutagenesis, Impairment of Fertility
In a 2 year study, rats were given methimazole
at doses of 0.5, 3, and 18 mg/kg/day. These doses were 0.3, 2, and
12 times the 15 mg/day maximum human maintenance dose
(when calculated on the basis
of surface area). Thyroid
hyperplasia, adenoma,
and carcinoma developed
in rats at the two higher doses. The clinical
significance of these findings is unclear.
Pregnancy Category D
(See WARNINGS
.) Tapazole used judiciously
is an effective drug in
hyperthyroidism
complicated by pregnancy. In
many pregnant women, the thyroid
dysfunction diminishes
as the pregnancy proceeds;
consequently, a reduction
in dosage may be possible.
In some instances, use of
Tapazole can be discontinued 2 or 3 weeks before delivery.
Nursing Mothers
The drug appears in human
breast milk
and its use is contraindicated in nursing
mothers (see WARNINGS
).
Pediatric Use
See DOSAGE AND ADMINISTRATION.
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