Sulfameth-Trimeth Susp (cherry)
It is used to treat or prevent bacterial infections.
Drug Class
Antibiotic
Pharmacologic Class
Folate Antagonist; Sulfonamide
Pregnancy Category
Category D
FDA Approved
Aug 1973
DEA Schedule
Not Controlled
Overview
What is this medicine?
This medicine is an antibiotic that combines two drugs, sulfamethoxazole and trimethoprim, to treat various bacterial infections. It works by stopping bacteria from making a substance they need to grow and multiply. The cherry flavor helps make it easier to take, especially for children.
How to Use This Medicine
Taking Your Medication Correctly
To get the most benefit from your medication, follow these steps:
Take your medication exactly as directed by your doctor.
Read all the information provided with your medication and follow the instructions carefully.
You can take your medication with or without food. If it causes stomach upset, take it with food.
Swallow your medication with a full glass of water.
Take your medication at the same time every day to establish a routine.
Continue taking your medication as directed by your doctor or healthcare provider, even if you start to feel better.
Additional Tips
Drink plenty of non-caffeinated liquids, unless your doctor advises you to limit your fluid intake.
Before taking a liquid dose, shake the medication well.
Measure liquid doses carefully using the measuring device provided with your medication. If one is not provided, ask your pharmacist for a suitable device.
Storing and Disposing of Your Medication
Store your medication at room temperature, away from light and moisture.
Keep your medication in a dry place, such as a closet or drawer, and avoid storing it in the bathroom.
Keep all medications out of the reach of children and pets.
Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so by your pharmacist. Check with your pharmacist for guidance on the best way to dispose of your medication, and consider participating in a local drug take-back program.
What to Do If You Miss a Dose
If you miss a dose, take it as soon as you remember.
If it's almost time for your next dose, skip the missed dose and resume your regular schedule.
Do not take two doses at the same time or take extra doses to make up for a missed dose.
To get the most benefit from your medication, follow these steps:
Take your medication exactly as directed by your doctor.
Read all the information provided with your medication and follow the instructions carefully.
You can take your medication with or without food. If it causes stomach upset, take it with food.
Swallow your medication with a full glass of water.
Take your medication at the same time every day to establish a routine.
Continue taking your medication as directed by your doctor or healthcare provider, even if you start to feel better.
Additional Tips
Drink plenty of non-caffeinated liquids, unless your doctor advises you to limit your fluid intake.
Before taking a liquid dose, shake the medication well.
Measure liquid doses carefully using the measuring device provided with your medication. If one is not provided, ask your pharmacist for a suitable device.
Storing and Disposing of Your Medication
Store your medication at room temperature, away from light and moisture.
Keep your medication in a dry place, such as a closet or drawer, and avoid storing it in the bathroom.
Keep all medications out of the reach of children and pets.
Dispose of unused or expired medications properly. Do not flush them down the toilet or pour them down the drain unless instructed to do so by your pharmacist. Check with your pharmacist for guidance on the best way to dispose of your medication, and consider participating in a local drug take-back program.
What to Do If You Miss a Dose
If you miss a dose, take it as soon as you remember.
If it's almost time for your next dose, skip the missed dose and resume your regular schedule.
Do not take two doses at the same time or take extra doses to make up for a missed dose.
Lifestyle & Tips
- Drink plenty of fluids (6-8 glasses of water daily) to help prevent kidney stones and ensure proper kidney function.
- Avoid prolonged exposure to sunlight or tanning beds, as this medication can make your skin more sensitive to the sun (photosensitivity). Use sunscreen and wear protective clothing.
- Take the full course of medication as prescribed, even if you start feeling better, to ensure the infection is fully treated and prevent antibiotic resistance.
- Shake the suspension well before each use.
- Use an accurate measuring device (oral syringe or dosing spoon) provided by your pharmacist, not a household spoon, to ensure correct dosing.
Available Forms & Alternatives
Dosing & Administration
Adult Dosing
Standard Dose:
For uncomplicated UTI: 160 mg Trimethoprim (TMP) / 800 mg Sulfamethoxazole (SMX) orally every 12 hours for 3 to 14 days, depending on infection severity. For PCP treatment: 15-20 mg/kg/day TMP (75-100 mg/kg/day SMX) orally in 3-4 divided doses for 14-21 days.
Condition-Specific Dosing:
uncomplicated_uti:
160 mg TMP / 800 mg SMX q12h for 3-14 days
pcp_treatment:
15-20 mg/kg/day TMP (75-100 mg/kg/day SMX) in 3-4 divided doses for 14-21 days
pcp_prophylaxis:
160 mg TMP / 800 mg SMX orally once daily or 3 times per week
Pediatric Dosing
Neonatal:
Contraindicated in infants less than 2 months of age due to risk of kernicterus.
Infant:
Contraindicated in infants less than 2 months of age. For infants > 2 months, dosing is weight-based.
Child:
For UTI: 8 mg/kg/day TMP (40 mg/kg/day SMX) orally in 2 divided doses every 12 hours for 10 days. For PCP prophylaxis: 5 mg/kg/day TMP (25 mg/kg/day SMX) orally in 2 divided doses daily or 3 times per week.
Adolescent:
Same as adult dosing for weight-appropriate adolescents.
Dose Adjustments
Renal Impairment:
Mild:
CrCl > 30 mL/min: No dosage adjustment needed.
Moderate:
CrCl 15-30 mL/min: Reduce dose by 50% (e.g., administer standard dose every 24 hours or half the standard dose every 12 hours).
Severe:
CrCl < 15 mL/min: Not recommended unless plasma concentrations can be monitored. If used, reduce dose by 75% (e.g., administer standard dose every 48 hours or one-quarter the standard dose every 12 hours).
Dialysis:
Hemodialysis: Administer 50% of the usual dose after each dialysis session. Peritoneal dialysis: Not well studied, generally avoid or use with extreme caution and monitor levels.
Hepatic Impairment:
Mild:
No specific adjustment recommended.
Moderate:
Use with caution; monitor for signs of toxicity. No specific dose adjustment guidelines.
Severe:
Use with extreme caution or avoid due to potential for hepatic necrosis and impaired drug metabolism. No specific dose adjustment guidelines.
Pharmacology
Mechanism of Action
Sulfamethoxazole (SMX) inhibits bacterial dihydrofolate synthetase, preventing the synthesis of dihydrofolic acid. Trimethoprim (TMP) inhibits bacterial dihydrofolate reductase, blocking the conversion of dihydrofolic acid to tetrahydrofolic acid. This sequential blockade of two enzymes in the folic acid synthesis pathway results in a synergistic bactericidal effect, as bacteria cannot synthesize essential purines, DNA, and RNA.
Pharmacokinetics
Absorption:
Bioavailability:
Oral bioavailability is approximately 90-100% for both components.
Tmax:
Trimethoprim: 1-4 hours; Sulfamethoxazole: 2-4 hours.
FoodEffect:
Absorption is not significantly affected by food, but administration with food may reduce gastrointestinal upset.
Distribution:
Vd:
Trimethoprim: Approximately 1.3 L/kg; Sulfamethoxazole: Approximately 0.36 L/kg.
ProteinBinding:
Trimethoprim: Approximately 44%; Sulfamethoxazole: Approximately 70%.
CnssPenetration:
Yes, both components penetrate the cerebrospinal fluid, achieving concentrations sufficient for therapeutic effect in CNS infections.
Elimination:
HalfLife:
Trimethoprim: 8-10 hours; Sulfamethoxazole: 10-12 hours.
Clearance:
Primarily renal clearance.
ExcretionRoute:
Renal (glomerular filtration and tubular secretion).
Unchanged:
Trimethoprim: Approximately 50-60%; Sulfamethoxazole: Approximately 10-30%.
Pharmacodynamics
OnsetOfAction:
Rapid, typically within 1-4 hours after oral administration.
PeakEffect:
Correlates with Tmax, generally within 2-4 hours.
DurationOfAction:
Approximately 12 hours, supporting twice-daily dosing.
Confidence:
High
Safety & Warnings
BLACK BOX WARNING
FATALITIES ASSOCIATED WITH THE ADMINISTRATION OF SULFONAMIDES, ALTHOUGH RARE, HAVE OCCURRED DUE TO SEVERE REACTIONS INCLUDING STEVENS-JOHNSON SYNDROME, TOXIC EPIDERMAL NECROLYSIS, FULMINANT HEPATIC NECROSIS, AGRANULOCYTOSIS, APLASTIC ANEMIA, AND OTHER BLOOD DYSCRASIAS. SULFONAMIDES, INCLUDING SULFONAMIDE-CONTAINING PRODUCTS SUCH AS SULFAMETHOXAZOLE AND TRIMETHOPRIM, SHOULD BE DISCONTINUED AT THE FIRST APPEARANCE OF SKIN RASH OR ANY SIGN OF ADVERSE REACTION. CLINICAL SIGNS SUCH AS RASH, SORE THROAT, FEVER, ARTHRALGIA, PALLOR, PURPURA OR JAUNDICE MAY BE EARLY INDICATIONS OF SERIOUS REACTIONS. COUGH, SHORTNESS OF BREATH, AND PULMONARY INFILTRATES ARE ALSO REPORTED AS SIGNS OF HYPERSENSITIVITY REACTIONS.
Side Effects
Urgent Side Effects: Seek Medical Help Right Away
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor immediately or seek emergency medical attention:
Signs of an allergic reaction: rash, hives, itching, red, swollen, blistered, or peeling skin (with or without fever), wheezing, tightness in the chest or throat, difficulty breathing, swallowing, or talking, unusual hoarseness, or swelling of the mouth, face, lips, tongue, or throat.
Signs of high potassium levels: abnormal heartbeat, confusion, weakness, lightheadedness, dizziness, numbness or tingling, or shortness of breath.
Signs of low blood sugar: dizziness, headache, drowsiness, weakness, shaking, rapid heartbeat, confusion, hunger, or sweating.
Signs of kidney problems: inability to urinate, changes in urine output, blood in the urine, or sudden weight gain.
Signs of low sodium levels: headache, difficulty focusing, memory problems, confusion, weakness, seizures, or balance changes.
Signs of lung or breathing problems: shortness of breath, difficulty breathing, cough, or fever.
Signs of pancreatitis (pancreas problem): severe stomach pain, severe back pain, or severe nausea and vomiting.
Muscle or joint pain.
Purple patches on the skin or mouth.
Hallucinations (seeing or hearing things that are not there).
Depression or mood changes.
Abnormal burning, numbness, or tingling sensations.
Ringing in the ears.
Swollen glands.
Chest pain.
Pale skin.
Severe dizziness or fainting.
Diarrhea (common with antibiotics, but rarely, a severe form called C. diff-associated diarrhea (CDAD) may occur, which can lead to a life-threatening bowel problem). If you experience stomach pain, cramps, or loose, watery, or bloody stools, contact your doctor immediately.
Rare but Serious Side Effects
Liver problems, blood problems, or severe skin reactions (Stevens-Johnson syndrome/toxic epidermal necrolysis) have occurred with sulfa drugs, sometimes with fatal outcomes. Seek medical help right away if you experience a rash, red, swollen, blistered, or peeling skin, red or irritated eyes, mouth, throat, nose, or eye sores, fever, chills, sore throat, new or worsening cough, extreme fatigue or weakness, bruising or bleeding, or signs of liver problems (dark urine, fatigue, decreased appetite, nausea, stomach pain, light-colored stools, vomiting, or yellow skin and eyes).
Aseptic meningitis, a severe brain problem, has been associated with this medication. Contact your doctor immediately if you experience a headache, fever, chills, severe nausea and vomiting, stiff neck, rash, sensitivity to light, drowsiness, or confusion.
Hemophagocytic lymphohistiocytosis (HLH), a life-threatening immune system problem, has occurred with this medication. Seek medical help right away if you experience fever, swollen glands, rash, seizures, confusion, balance changes, or new or worsening difficulty walking.
Other Side Effects
Not everyone experiences side effects, and many people have only minor or no side effects. However, if you notice any of the following, contact your doctor or seek medical help:
Diarrhea, stomach pain, nausea, vomiting, or decreased appetite.
Reporting Side Effects
If you have questions about side effects or experience any side effects that bother you or do not go away, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Although rare, some people may experience severe and potentially life-threatening side effects while taking this medication. If you notice any of the following symptoms, contact your doctor immediately or seek emergency medical attention:
Signs of an allergic reaction: rash, hives, itching, red, swollen, blistered, or peeling skin (with or without fever), wheezing, tightness in the chest or throat, difficulty breathing, swallowing, or talking, unusual hoarseness, or swelling of the mouth, face, lips, tongue, or throat.
Signs of high potassium levels: abnormal heartbeat, confusion, weakness, lightheadedness, dizziness, numbness or tingling, or shortness of breath.
Signs of low blood sugar: dizziness, headache, drowsiness, weakness, shaking, rapid heartbeat, confusion, hunger, or sweating.
Signs of kidney problems: inability to urinate, changes in urine output, blood in the urine, or sudden weight gain.
Signs of low sodium levels: headache, difficulty focusing, memory problems, confusion, weakness, seizures, or balance changes.
Signs of lung or breathing problems: shortness of breath, difficulty breathing, cough, or fever.
Signs of pancreatitis (pancreas problem): severe stomach pain, severe back pain, or severe nausea and vomiting.
Muscle or joint pain.
Purple patches on the skin or mouth.
Hallucinations (seeing or hearing things that are not there).
Depression or mood changes.
Abnormal burning, numbness, or tingling sensations.
Ringing in the ears.
Swollen glands.
Chest pain.
Pale skin.
Severe dizziness or fainting.
Diarrhea (common with antibiotics, but rarely, a severe form called C. diff-associated diarrhea (CDAD) may occur, which can lead to a life-threatening bowel problem). If you experience stomach pain, cramps, or loose, watery, or bloody stools, contact your doctor immediately.
Rare but Serious Side Effects
Liver problems, blood problems, or severe skin reactions (Stevens-Johnson syndrome/toxic epidermal necrolysis) have occurred with sulfa drugs, sometimes with fatal outcomes. Seek medical help right away if you experience a rash, red, swollen, blistered, or peeling skin, red or irritated eyes, mouth, throat, nose, or eye sores, fever, chills, sore throat, new or worsening cough, extreme fatigue or weakness, bruising or bleeding, or signs of liver problems (dark urine, fatigue, decreased appetite, nausea, stomach pain, light-colored stools, vomiting, or yellow skin and eyes).
Aseptic meningitis, a severe brain problem, has been associated with this medication. Contact your doctor immediately if you experience a headache, fever, chills, severe nausea and vomiting, stiff neck, rash, sensitivity to light, drowsiness, or confusion.
Hemophagocytic lymphohistiocytosis (HLH), a life-threatening immune system problem, has occurred with this medication. Seek medical help right away if you experience fever, swollen glands, rash, seizures, confusion, balance changes, or new or worsening difficulty walking.
Other Side Effects
Not everyone experiences side effects, and many people have only minor or no side effects. However, if you notice any of the following, contact your doctor or seek medical help:
Diarrhea, stomach pain, nausea, vomiting, or decreased appetite.
Reporting Side Effects
If you have questions about side effects or experience any side effects that bother you or do not go away, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.
Seek Immediate Medical Attention If You Experience:
- New or worsening skin rash, especially if it's severe, blistering, peeling, or accompanied by fever, sore throat, or eye irritation (could be a sign of a severe skin reaction like Stevens-Johnson Syndrome).
- Unexplained fever, chills, sore throat, or unusual tiredness (could indicate blood problems).
- Yellowing of the skin or eyes (jaundice), dark urine, or pale stools (signs of liver problems).
- Severe or persistent diarrhea, especially if it contains blood or mucus (could be a sign of C. difficile infection).
- Sudden muscle weakness, irregular heartbeat, or numbness/tingling (signs of high potassium levels).
- Signs of kidney stones (severe pain in your side or back, blood in urine, painful urination).
Before Using This Medicine
Before Taking This Medication: Important Information to Share with Your Doctor
It is essential to inform your doctor about the following conditions and situations to ensure safe treatment with this medication:
Any allergies you have, including allergies to this drug, its components, or other substances, such as foods or medications. Describe the allergic reactions you have experienced.
A history of anemia caused by a lack of folic acid.
Presence of kidney disease or liver disease.
Certain health conditions, including:
+ Asthma
+ Porphyria
+ Thyroid disease
+ Folate deficiency
+ Malabsorption
+ Poor nutrition
Long-term alcohol consumption or use of antiseizure medications.
A history of low platelet count when taking trimethoprim or sulfa (sulfonamide) drugs.
Concurrent use of the following medications:
+ Amantadine
+ Cyclosporine
+ Dofetilide
+ Indomethacin
+ Leucovorin
+ Methotrexate
+ Pyrimethamine
Recent or current use of the following drugs:
+ Benazepril
+ Captopril
+ Enalapril
+ Fosinopril
+ Lisinopril
+ Moexipril
+ Perindopril
+ Quinapril
+ Ramipril
+ Trandolapril
* Use of diuretics (water pills).
Special Considerations for Children:
If your child is under 2 months of age, do not administer this medication. It is not approved for use in infants younger than 2 months.
This list is not exhaustive, and it is crucial to discuss all your medications (prescription, over-the-counter, natural products, and vitamins) and health conditions with your doctor and pharmacist to ensure safe use of this medication. Never start, stop, or adjust the dosage of any medication without consulting your doctor.
It is essential to inform your doctor about the following conditions and situations to ensure safe treatment with this medication:
Any allergies you have, including allergies to this drug, its components, or other substances, such as foods or medications. Describe the allergic reactions you have experienced.
A history of anemia caused by a lack of folic acid.
Presence of kidney disease or liver disease.
Certain health conditions, including:
+ Asthma
+ Porphyria
+ Thyroid disease
+ Folate deficiency
+ Malabsorption
+ Poor nutrition
Long-term alcohol consumption or use of antiseizure medications.
A history of low platelet count when taking trimethoprim or sulfa (sulfonamide) drugs.
Concurrent use of the following medications:
+ Amantadine
+ Cyclosporine
+ Dofetilide
+ Indomethacin
+ Leucovorin
+ Methotrexate
+ Pyrimethamine
Recent or current use of the following drugs:
+ Benazepril
+ Captopril
+ Enalapril
+ Fosinopril
+ Lisinopril
+ Moexipril
+ Perindopril
+ Quinapril
+ Ramipril
+ Trandolapril
* Use of diuretics (water pills).
Special Considerations for Children:
If your child is under 2 months of age, do not administer this medication. It is not approved for use in infants younger than 2 months.
This list is not exhaustive, and it is crucial to discuss all your medications (prescription, over-the-counter, natural products, and vitamins) and health conditions with your doctor and pharmacist to ensure safe use of this medication. Never start, stop, or adjust the dosage of any medication without consulting your doctor.
Precautions & Cautions
It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. Regular blood work and laboratory tests, as directed by your doctor, are crucial to monitor your condition.
This medication may interfere with certain laboratory tests, so it is vital to notify all your healthcare providers and laboratory personnel that you are taking this drug. Do not exceed the recommended duration of treatment, as this may increase the risk of a second infection.
If you have a deficiency of the enzyme glucose-6-phosphate dehydrogenase (G6PD), you may be more susceptible to anemia. Individuals of African, South Asian, Middle Eastern, and Mediterranean descent are more likely to have low G6PD levels.
If you have diabetes, it is crucial to closely monitor your blood sugar levels. Additionally, consult your doctor before consuming alcohol while taking this medication.
You may be more prone to sunburn while taking this drug, so exercise caution when exposed to sunlight. If you experience increased sensitivity to the sun, inform your doctor promptly.
A severe and potentially life-threatening reaction may occur, characterized by symptoms such as fever, rash, or swollen glands, accompanied by problems in organs like the liver, kidney, blood, heart, muscles and joints, or lungs. If you have any concerns, discuss them with your doctor.
If you are 65 years or older, use this medication with caution, as you may be more susceptible to side effects.
This medication may harm an unborn baby if taken during pregnancy. If you become pregnant or suspect you are pregnant while taking this drug, contact your doctor immediately.
If you are breastfeeding, consult your doctor to discuss any potential risks to your baby.
This medication may interfere with certain laboratory tests, so it is vital to notify all your healthcare providers and laboratory personnel that you are taking this drug. Do not exceed the recommended duration of treatment, as this may increase the risk of a second infection.
If you have a deficiency of the enzyme glucose-6-phosphate dehydrogenase (G6PD), you may be more susceptible to anemia. Individuals of African, South Asian, Middle Eastern, and Mediterranean descent are more likely to have low G6PD levels.
If you have diabetes, it is crucial to closely monitor your blood sugar levels. Additionally, consult your doctor before consuming alcohol while taking this medication.
You may be more prone to sunburn while taking this drug, so exercise caution when exposed to sunlight. If you experience increased sensitivity to the sun, inform your doctor promptly.
A severe and potentially life-threatening reaction may occur, characterized by symptoms such as fever, rash, or swollen glands, accompanied by problems in organs like the liver, kidney, blood, heart, muscles and joints, or lungs. If you have any concerns, discuss them with your doctor.
If you are 65 years or older, use this medication with caution, as you may be more susceptible to side effects.
This medication may harm an unborn baby if taken during pregnancy. If you become pregnant or suspect you are pregnant while taking this drug, contact your doctor immediately.
If you are breastfeeding, consult your doctor to discuss any potential risks to your baby.
Overdose Information
Overdose Symptoms:
- Nausea
- Vomiting
- Diarrhea
- Anorexia
- Headache
- Dizziness
- Confusion
- Bone marrow depression (e.g., megaloblastic anemia, leukopenia, thrombocytopenia)
- Fever
- Jaundice
- Crystalluria
- Hematuria
What to Do:
In case of suspected overdose, seek immediate medical attention or call a poison control center. Call 1-800-222-1222. Treatment may include gastric lavage, forced diuresis, urine alkalinization to increase sulfamethoxazole excretion, and administration of leucovorin (folinic acid) to counteract trimethoprim's effects on bone marrow.
Drug Interactions
Contraindicated Interactions
- Dofetilide (increased dofetilide levels, risk of QT prolongation and Torsades de Pointes)
Major Interactions
- Warfarin (potentiates anticoagulant effect, increased bleeding risk)
- Methotrexate (increased methotrexate toxicity, including bone marrow suppression)
- Potassium-sparing diuretics (e.g., spironolactone, amiloride), ACE inhibitors, ARBs (increased risk of hyperkalemia)
- Phenytoin (increased phenytoin levels, risk of toxicity)
- Digoxin (increased digoxin levels, risk of toxicity)
- Cyclosporine (increased risk of nephrotoxicity and decreased cyclosporine levels)
- Azathioprine, Mercaptopurine (increased risk of myelosuppression)
Moderate Interactions
- Oral hypoglycemics (sulfonylureas) (potentiates hypoglycemic effect)
- Rifampin (decreased trimethoprim levels)
- Procainamide (increased procainamide levels)
- Amantadine (increased amantadine levels, risk of toxicity)
- Lamivudine (increased lamivudine levels)
- Zidovudine (increased risk of hematologic toxicity)
Minor Interactions
- Tricyclic antidepressants (potential for increased TCA levels)
- Indomethacin (increased sulfamethoxazole levels)
Monitoring
Baseline Monitoring
Complete Blood Count (CBC) with differential
Rationale: To establish baseline hematologic parameters and identify pre-existing cytopenias, as SMX/TMP can cause bone marrow suppression.
Timing: Prior to initiation of therapy.
Renal Function (BUN, Serum Creatinine, eGFR)
Rationale: To assess baseline renal function, as the drug is primarily renally eliminated and dose adjustments are required in renal impairment. Also, to monitor for potential nephrotoxicity.
Timing: Prior to initiation of therapy.
Liver Function Tests (ALT, AST, Bilirubin)
Rationale: To establish baseline hepatic function, as SMX/TMP can cause hepatotoxicity.
Timing: Prior to initiation of therapy.
Serum Potassium
Rationale: To establish baseline potassium levels, especially in patients at risk for hyperkalemia (e.g., elderly, renal impairment, concomitant medications).
Timing: Prior to initiation of therapy.
Routine Monitoring
Complete Blood Count (CBC) with differential
Frequency: Weekly for prolonged therapy (e.g., PCP treatment/prophylaxis) or if signs of myelosuppression develop. Less frequently for short-course therapy.
Target: Within normal limits; monitor for significant decreases in WBC, platelets, or hemoglobin.
Action Threshold: Discontinue if significant myelosuppression (e.g., severe neutropenia < 500/mm³, thrombocytopenia < 50,000/mm³).
Renal Function (BUN, Serum Creatinine, eGFR)
Frequency: Weekly for prolonged therapy or if renal impairment is present/suspected. For short courses, monitor if baseline impairment or risk factors.
Target: Within patient's baseline or acceptable limits.
Action Threshold: Significant increase in creatinine (>25% from baseline or above upper limit of normal) may warrant dose adjustment or discontinuation.
Serum Potassium
Frequency: Weekly for prolonged therapy, especially in elderly, renal impairment, or with concomitant hyperkalemia-inducing drugs.
Target: 3.5-5.0 mEq/L.
Action Threshold: Potassium > 5.5 mEq/L may require intervention or discontinuation.
Liver Function Tests (ALT, AST, Bilirubin)
Frequency: Periodically for prolonged therapy or if signs/symptoms of hepatotoxicity develop.
Target: Within normal limits.
Action Threshold: Significant elevation (e.g., >3x ULN) may warrant discontinuation.
Symptom Monitoring
- Skin rash (especially severe, blistering, or widespread)
- Fever
- Sore throat
- Unusual bleeding or bruising
- Jaundice (yellowing of skin or eyes)
- Dark urine
- Pale stools
- Severe or persistent diarrhea (may indicate C. difficile infection)
- Signs of hyperkalemia (muscle weakness, fatigue, palpitations, paresthesias)
- Signs of kidney stones (flank pain, hematuria)
Special Patient Groups
Pregnancy
Contraindicated in pregnancy, especially during the first and third trimesters, due to potential risks to the fetus.
Trimester-Specific Risks:
First Trimester:
Category D. Folate antagonism by trimethoprim may interfere with folic acid metabolism, potentially increasing the risk of neural tube defects. Avoid unless the potential benefit justifies the potential risk.
Second Trimester:
Category D. Use with caution. Risks are generally lower than in the first or third trimesters, but still considered Category D.
Third Trimester:
Category D. Sulfamethoxazole can displace bilirubin from albumin binding sites, increasing the risk of kernicterus in the neonate, especially if administered near term. Avoid use during the last few weeks of pregnancy.
Lactation
Generally not recommended during breastfeeding, especially for premature infants, infants with hyperbilirubinemia, or infants with G6PD deficiency, due to the risk of kernicterus and hemolytic anemia.
Infant Risk:
Moderate risk (L3). Sulfamethoxazole and trimethoprim are excreted into breast milk. Potential for kernicterus in jaundiced or premature infants, and hemolytic anemia in G6PD deficient infants. Monitor breastfed infants for rash, diarrhea, and jaundice. Consider alternative antibiotics if possible, especially in the first 2 months postpartum.
Pediatric Use
Contraindicated in infants less than 2 months of age due to the risk of kernicterus (displacement of bilirubin from albumin binding sites). Use with caution in children with G6PD deficiency due to risk of hemolytic anemia. Dosing is weight-based for children older than 2 months.
Geriatric Use
Increased risk of adverse reactions, particularly hyperkalemia, renal impairment, bone marrow suppression (especially with concomitant ACE inhibitors/ARBs or potassium-sparing diuretics), and severe dermatologic reactions (SJS/TEN). Close monitoring of renal function, potassium levels, and CBC is essential. Lower doses or extended dosing intervals may be necessary.
Clinical Information
Clinical Pearls
- Always ensure adequate hydration to prevent crystalluria and kidney stone formation.
- Advise patients about photosensitivity and recommend sun protection.
- Be vigilant for signs of severe skin reactions (rash, fever, mucosal lesions) and instruct patients to discontinue the drug immediately and seek medical attention if these occur.
- Monitor potassium levels, especially in elderly patients, those with renal impairment, or those on concomitant medications that increase potassium (e.g., ACE inhibitors, ARBs, potassium-sparing diuretics).
- Contraindicated in infants < 2 months due to kernicterus risk.
- The cherry flavor can improve palatability, especially for pediatric patients, but ensure proper measurement with an oral syringe or dosing spoon.
- Consider folate supplementation in patients on long-term therapy or those at risk for folate deficiency (e.g., elderly, malnourished, or those with pre-existing bone marrow suppression) to mitigate trimethoprim's antifolate effects.
Alternative Therapies
- Fluoroquinolones (e.g., Ciprofloxacin, Levofloxacin) for UTIs or respiratory infections
- Beta-lactam antibiotics (e.g., Amoxicillin, Cephalexin) for UTIs or other bacterial infections
- Macrolides (e.g., Azithromycin, Clarithromycin) for respiratory infections or certain atypical infections
- Tetracyclines (e.g., Doxycycline) for various bacterial infections
- Clindamycin or Atovaquone for PCP treatment/prophylaxis in patients intolerant to SMX/TMP
Cost & Coverage
Average Cost:
Varies widely, typically $10-$50 per 100 mL suspension
Generic Available:
Yes
Insurance Coverage:
Tier 1 or Tier 2 (Generic)
General Drug Facts
If your symptoms or health issues persist or worsen, it's essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so be sure to check with your pharmacist for more information. If you have any questions or concerns about this medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek medical attention. When seeking help, be prepared to provide details about the overdose, including the medication taken, the amount, and the time it occurred.