PRECAUTIONS
General
Prescribing Sulfamethoxazole and Trimethoprim Oral
Suspension in the absence of a proven or strongly suspected bacterial infection
or a prophylactic indication is unlikely to provide benefit to the patient and increases
the risk of the development of drug-resistant bacteria.
Sulfamethoxazole and Trimethoprim Oral Suspension should
be given with caution to patients with impaired renal or hepatic function, to
those with possible folate deficiency (e.g., the elderly, chronic alcoholics,
patients receiving anticonvulsant therapy, patients with malabsorption
syndrome, and patients in malnutrition states) and to those with severe
allergies or bronchial asthma. In glucose-6-phosphate dehydrogenase deficient
individuals, hemolysis may occur. This reaction is frequently dose-related.
Use In The Elderly
There may be an increased risk of severe adverse
reactions in elderly patients, particularly when complicating conditions exist,
e.g., impaired kidney and/or liver function, or concomitant use of other drugs.
Severe skin reactions, generalized bone marrow suppression (see WARNINGS
and ADVERSE REACTIONS sections) or a specific decrease in platelets
(with or without purpura) are the most frequently reported severe adverse
reactions in elderly patients. In those concurrently receiving certain diuretics,
primarily thiazides, an increased incidence of thrombocytopenia with purpura
has been reported. Appropriate dosage adjustments should be made for patients
with impaired kidney function (see DOSAGE AND ADMINISTRATION section).
Use In The Treatment Of And Prophylaxis For Pneumocystis
Carinii Pneumonia In Patients With Acquired Immunodeficiency Syndrome (AIDS)
AIDS patients may not tolerate or respond to
sulfamethoxazole and trimethoprim oral suspension in the same manner as
non-AIDS patients. The incidence of side effects, particularly rash, fever, leucopenia
and elevated aminotransferase (transaminase) values with sulfamethoxazole and
trimethoprim therapy in AIDS patients who are being treated for Pneumocystic
carinii pneumonia has been reported to be greatly increased compared with
the incidence normally associated with the use of sulfamethoxazole and trimethoprim
in non-AIDS patients. Adverse effects are generally less severe in patients
receiving sulfamethoxazole and trimethoprim for prophylaxis. A history of mild
intolerance to sulfamethoxazole and trimethoprim in AIDS patients does not
appear to predict intolerance of subsequent secondary prophylaxis.5
However, if a patient develops skin rash or any sign of adverse reaction,
therapy with sulfamethoxazole and trimethoprim oral suspension should be
reevaluated (see WARNINGS).
Laboratory Tests
Complete blood counts should be done frequently in
patients receiving sulfamethoxazole and trimethoprim; if a significant
reduction in the count of any formed blood element is noted, this drug product
should be discontinued. Urinalysis with careful microscopic examination and
renal function tests should be performed during therapy, particularly for those
patients with impaired renal function.
REFERENCES
5. Hardy DW, et al. A controlled trial of
trimethoprim-sulfamethoxazole or aerosolized pentamidine for secondary
prophylaxis of Pneumocystis carinii pneumonia in patients with the acquired immunodeficiency
syndrome. N Engl J Med. 1992; 327:1842-1848.
Carcinogenesis, Mutagenesis, Impairment Of Fertility
Carcinogenesis
Long-term studies in animals to evaluate carcinogenic
potential have not been conducted with sulfamethoxazole and trimethoprim.
Mutagenesis
Bacterial mutagenic studies have not been performed with
sulfamethoxazole and trimethoprim in combination. Trimethoprim was demonstrated
to be nonmutagenic in the Ames assay. No chromosomal damage was observed in
human leukocytes in vitro with sulfamethoxazole and trimethoprim alone or in combination;
the concentrations used exceeded blood levels of these compounds following
therapy with sulfamethoxazole and trimethoprim. Observations of leukocytes
obtained from patients treated with sulfamethoxazole and trimethoprim revealed
no chromosomal abnormalities.
Impairment Of Fertility
No adverse effects on fertility or general reproductive
performance were observed in rats given oral dosages as high as 70 mg/kg/day
trimethoprim plus 350 mg/kg/day sulfamethoxazole.
Pregnancy
Teratogenic Effects
Pregnancy Category C. In rats, oral doses of 533
mg/kg sulfamethoxazole or 200 mg/kg trimethoprim produced teratological effects
manifested mainly as cleft palates.
The highest dose which did not cause cleft palates in
rats was 512 mg/kg sulfamethoxazole or 192 mg/kg trimethoprim when administered
separately. In two studies in rats, no teratology was observed when 512 mg/kg
of sulfamethoxazole was used in combination with 128 mg/kg of trimethoprim. In
one study, however, cleft palates were observed in one litter out of 9 when 355
mg/kg of sulfamethoxazole was used in combination with 88 mg/kg of
trimethoprim.
In some rabbit studies, an overall increase in fetal loss
(dead and resorbed and malformed conceptuses) was associated with doses of
trimethoprim 6 times the human therapeutic dose.
While there are no large, well-controlled studies on the
use of sulfamethoxazole and trimethoprim in pregnant women, Brumfitt and
Pursell6, in a retrospective study, reported the outcome of 186 pregnancies
during which the mother received either placebo or sulfamethoxazole and
trimethoprim. The incidence of congenital abnormalities was 4.5% (3 of 66) in
those who received placebo and 3.3% (4 of 120) in those receiving
sulfamethoxazole and trimethoprim. There were no abnormalities in the 10 children
whose mothers received the drug during the first trimester. In a separate
survey, Brumfitt and Pursell also found no congenital abnormalities in 35
children whose mothers had received oral sulfamethoxazole and trimethoprim at
the time of conception or shortly thereafter.
Because sulfamethoxazole and trimethoprim may interfere
with folic acid metabolism, this product should be used during pregnancy only
if the potential benefit justifies the potential risk to the fetus.
Nonteratogenic Effects
See CONTRAINDICATIONS section.
Nursing Mothers
See CONTRAINDICATIONS section.
Pediatric Use
Sulfamethoxazole and Trimethoprim Oral Suspension is not
recommended for pediatric patients younger than 2 months of age (see
INDICATIONS AND USAGE and CONTRAINDICATIONSsections).
REFERENCES
6. Brumfitt W, Pursell R. Trimethoprim/Sulfamethoxazole
in the Treatment of Bacteriuria in Women. J Infect Dis. Nov. 1973; 128(Suppl):
S657-S663.