• Dosage of Primsulfon in details
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Dosage of Primsulfon in details

Primsulfon Dosage

Generic name: Trimethoprim (Primsulfon) 80mg, Sulfamethoxazole (Primsulfon) 400mg

Dosage form: tablet

The information at Drugs.com is not a substitute for medical advice. Always consult your doctor or pharmacist.

Contraindicated in pediatric patients less than 2 months of age.

Urinary Tract Infections and Shigellosis in Adults and Pediatric Patients and Acute Otitis Media in Pediatric Patients:

Adults: The usual adult dosage in the treatment of urinary tract infections is one Primsulfon DS (double strength) tablet, two Primsulfon tablets, or four teaspoonfuls (20 mL) Primsulfon Suspension every 12 hours for 10 to 14 days. An identical daily dosage is used for 5 days in the treatment of shigellosis.

Pediatric Patients: The recommended dose for pediatric patients with urinary tract infections or acute otitis media is 8 mg/kg Trimethoprim (Primsulfon) and 40 mg/kg Sulfamethoxazole (Primsulfon) per 24 hours, given in two divided doses every 12 hours for 10 days. An identical daily dosage is used for 5 days in the treatment of shigellosis. The following table is a guideline for the attainment of this

Dosage:

Pediatric Patients: Two Months of Age or Older

Weight		Dose-Every 12 Hours
lb	kg	Teaspoonfuls	Tablets
22	10	1 (5 mL)
44	20	2 (10 mL)	1
66	30	3 (15 mL)	1 1/2
88	40	4 (20 mL)	2 (or 1 DS Tablet)

For Patients With Impaired Renal Function: When renal function is impaired, a reduced dosage should be employed using the following table:

Creatinine	Recommended
Clearance	Dosage
(mL/min)	Regimen
Above 30	Use Standard Regimen
15-30	1/2 the Usual Regimen
Below 15	Use Not Recommended

Acute Exacerbations of Chronic Bronchitis in Adults:

The usual adult dosage in the treatment of acute exacerbations of chronic bronchitis is one Primsulfon DS (double strength) tablet, two Primsulfon tablets, or four teaspoonfuls (20 mL) Primsulfon Suspension every 12 hours for 14 days.

Travelers' Diarrhea in Adults:

For the treatment of travelers' diarrhea, the usual adult dosage is one Primsulfon DS (double strength) tablet, two Primsulfon tablets, or four teaspoonfuls (20 mL) of Primsulfon Suspension every 12 hours for 5 days.

Pneumocystis Carinii Pneumonia:

Treatment:

Adults and Pediatric Patients: The recommended dosage for treatment of patients with documented Pneumocystis carinii pneumonia is 15 to 20 mg/kg Trimethoprim (Primsulfon) and 75 to 100 mg/kg Sulfamethoxazole (Primsulfon) per 24 hours given in equally divided doses every 6 hours for 14 to 21 days. The following table is a guideline for the upper limit of this

Dosage:

Weight Dose – Every 6 Hours
lb	kg	Teaspoonfuls	Tablets
18	8	1 (5 mL)
35	16	2 (10 mL)	1
53	24	3 (15 mL)	1 1⁄2
70	32	4 (20 mL)	2 (or 1 DS Tablet)
88	40	5 (25 mL)	2 1⁄2
106	48	6 (30 mL)	3 (or 1 1⁄2 DS Tablets)
141	64	8 (40 mL)	4 (or 2 DS Tablets)
176	80	10 (50 mL)	5 (or 2 1⁄2 DS Tablets)

For the lower limit dose (15 mg/kg Trimethoprim (Primsulfon) and 75 mg/kg Sulfamethoxazole (Primsulfon) per 24 hours) administer 75% of the dose in the above table.

Prophylaxis:

Adults: The recommended dosage for prophylaxis in adults is one Primsulfon DS (double strength) tablet daily.

Pediatric Patients: For pediatric patients, the recommended dose is 150 mg/m2/day Trimethoprim (Primsulfon) with 750 mg/m2/day Sulfamethoxazole (Primsulfon) given orally in equally divided doses twice a day, on 3 consecutive days per week. The total daily dose should not exceed 320 mg Trimethoprim (Primsulfon) and 1,600 mg Sulfamethoxazole (Primsulfon). The following table is a guideline for the attainment of this dosage in pediatric patients:

Body Surface Area Dose–every 12 hours
(m2)	Teaspoonfuls	Tablets
0.26	1⁄2 (2.5 mL)
0.53	1 (5 mL)	1⁄2
1.06	2 (10 mL)	1

More about Primsulfon (Sulfamethoxazole (Primsulfon) / Trimethoprim (Primsulfon))

• Side Effects
• During Pregnancy
• Dosage Information
• Drug Interactions
• Support Group
• 14 Reviews - Add your own review/rating
• Generic Availability

Consumer resources

• Primsulfon
• Primsulfon Suspension
• Primsulfon (Advanced Reading)
• Primsulfon Pediatric Suspension (Advanced Reading)

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Professional resources

• Primsulfon (FDA)

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What other drugs will affect Primsulfon?

Tell your doctor about all medicines you use, and those you start or stop using during your treatment with Primsulfon, especially:

• leucovorin; or

• methotrexate.

This list is not complete. Other drugs may interact with Primsulfon, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.

Primsulfon interactions

Potential for Primsulfon to Affect Other Drugs

Trimethoprim (Primsulfon) is an inhibitor of CYP2C8 as well as OCT2 transporter. Sulfamethoxazole (Primsulfon) is an inhibitor of CYP2C9. Caution is recommended when Primsulfon is co-administered with drugs that are substrates of CYP2C8 and 2C9 or OCT2.

In elderly patients concurrently receiving certain diuretics, primarily thiazides, an increased incidence of thrombocytopenia with purpura has been reported.

It has been reported that Primsulfon may prolong the prothrombin time in patients who are receiving the anticoagulant warfarin (a CYP2C9 substrate). This interaction should be kept in mind when Primsulfon is given to patients already on anticoagulant therapy, and the coagulation time should be reassessed.

Primsulfon may inhibit the hepatic metabolism of phenytoin (a CYP2C9 substrate). Primsulfon, given at a common clinical dosage, increased the phenytoin half-life by 39% and decreased the phenytoin metabolic clearance rate by 27%. When administering these drugs concurrently, one should be alert for possible excessive phenytoin effect.

Sulfonamides can also displace methotrexate from plasma protein binding sites and can compete with the renal transport of methotrexate, thus increasing free methotrexate concentrations.

There have been reports of marked but reversible nephrotoxicity with coadministration of Primsulfon and cyclosporine in renal transplant recipients.

Increased digoxin blood levels can occur with concomitant Primsulfon therapy, especially in elderly patients. Serum digoxin levels should be monitored.

Increased Sulfamethoxazole (Primsulfon) blood levels may occur in patients who are also receiving indomethacin.

Occasional reports suggest that patients receiving pyrimethamine as malaria prophylaxis in doses exceeding 25 mg weekly may develop megaloblastic anemia if Primsulfon is prescribed.

The efficacy of tricyclic antidepressants can decrease when coadministered with Primsulfon.

Primsulfon potentiates the effect of oral hypoglycemics that are metabolized by CYP2C8 (e.g., pioglitazone, repaglinide, and rosiglitazone) or CYP2C9 (e.g., glipizide and glyburide) or eliminated renally via OCT2 (e.g., metformin). Additional monitoring of blood glucose may be warranted.

In the literature, a single case of toxic delirium has been reported after concomitant intake of Primsulfon and amantadine (an OCT2 substrate). Cases of interactions with other OCT2 substrates, memantine and metformin, have also been reported.

In the literature, three cases of hyperkalemia in elderly patients have been reported after concomitant intake of Primsulfon and an angiotensin converting enzyme inhibitor.

Drug/Laboratory Test Interactions

Primsulfon, specifically the Trimethoprim (Primsulfon) component, can interfere with a serum methotrexate assay as determined by the competitive binding protein technique (CBPA) when a bacterial dihydrofolate reductase is used as the binding protein. No interference occurs, however, if methotrexate is measured by a radioimmunoassay (RIA).

The presence of Primsulfon may also interfere with the Jaffé alkaline picrate reaction assay for creatinine, resulting in overestimations of about 10% in the range of normal values.

References

1. DailyMed. "SULFAMETHOXAZOLE: DailyMed provides trustworthy information about marketed drugs in the United States. DailyMed is the official provider of FDA label information (package inserts).". https://dailymed.nlm.nih.gov/dailyme... (accessed September 17, 2018).
2. DailyMed. "POLYMYXIN B SULFATE; TRIMETHOPRIM SULFATE: DailyMed provides trustworthy information about marketed drugs in the United States. DailyMed is the official provider of FDA label information (package inserts).". https://dailymed.nlm.nih.gov/dailyme... (accessed September 17, 2018).
3. FDA/SPL Indexing Data. "JE42381TNV: The UNique Ingredient Identifier (UNII) is an alphanumeric substance identifier from the joint FDA/USP Substance Registration System (SRS).". https://www.fda.gov/ForIndustry/Data... (accessed September 17, 2018).

Reviews

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Information checked by Dr. Sachin Kumar, MD Pharmacology