Pharm
Sulfonamide
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Sulfonamide
, Bactrim, Sulfatrim, Co-trimoxazole, Trimethoprim Sulfamethoxazole, Septra, TMP-SMZ
See Also
Sulfonamide Allergy
Indications
Urinary Tract Infection
Pneumocystis carinii
prophylaxis and treatment
Contraindications
Avoid in infant under age 2 months
Sulfonamide Allergy
Adverse Effects
Gene
ral
Allergic Reaction
or
Anaphylaxis
See
Sulfonamide Allergy
Bone Marrow
suppression (
Agranulocytosis
)
Steven's Johnson Syndrome
Toxic Epidermal Necrolysis
Hyperkalemia
Related to trimethoprim component
Higher risk with underlying
Renal Insufficiency
Exacerbated by
ACE Inhibitor
,
Angiotensin Receptor Blocker
, and
Potassium
supplements
Adverse Effects
HIV patients (40-60% within 3 weeks)
Hepatitis
Neutropenia
Anemia
Hyponatremia
Hyperkalemia
(6% of patients, esp. elderly)
Nausea
or
Vomiting
Rash
Fever
Drug Interactions
Other drugs decrease Trimethoprim Sulfamethoxazole levels
Rifampin
Trimethoprim Sulfamethoxazole increases other drug levels
Phenytoin
(
Dilantin
)
Methotrexate
Warfarin
Trimethoprim Sulfamethoxazole increases
Warfarin
effects and may result in up to a 3 fold increase in INR
Monitor INR and plan 25-50%
Warfarin
dose reduction while on Trimethoprim Sulfamethoxazole
Hyperkalemia
risk
Increased risk with
ACE Inhibitor
s,
Angiotensin Receptor Blocker
s,
Spironolactone
Higher risk with age >65 years,
Renal Insufficiency
,
Diabetes Mellitus
and
Heart Failure
Significantly increased rate of hospitalization and sudden death
Avoid Septra use for longer than three days with these agents and comorbidities in age >65 years
Consider alternative antibiotics, holding antihypertensive or recheck
Serum Potassium
in 4-5 days
Fralick (2014) BMJ 349:g6196 +PMID:25359996 [PubMed]
References
Tarascon Pharmacopoeia, accessed online 8/8/2014
(2014) Presc lett 21(8): 47
Precautions
Prolonged use may cause very severe adverse reactions
Follow CBC in prolonged use
Hyperkalemia
risk (especially in
Renal Insufficiency
)
Preparations
Double Strength (DS)
Trimethoprim 160 mg
Sulfamethoxazole 800 mg
Single Strength (SS)
Trimethoprim 80 mg
Sulfamethoxazole 400 mg
Pediatric Suspension (40/200 per 5 ml)
Trimethoprim 40 mg per 5 ml
Sulfamethoxazole 200 mg per 5 ml
Dosing
Directions (regarding Sulfonamide component)
Take on an empty
Stomach
Take more than 1 hour before or two hours after food
Dosing
Children (Using 40/200 per 5 ml suspension)
Treatment
Dose 8 mg/kg/day of TMP component PO divided bid
For each 10 kg weight, dose 5 ml suspension bid (up to maximum of 20 ml/dose)
Examples
Age 2 months (5 kg): 2.5 ml orally twice daily
Age 1 year (10 kg): 5.0 ml orally twice daily
Age 3 years (15 kg): 7.5 ml orally twice daily
Age 5 years (20 kg): 10 ml orally twice daily
Prophylaxis of
Urinary Tract Infection
s
Dose: 4 mg/kg/day of Trimethoprim dosed once daily
Avoid use with marked
Hyperbilirubinemia
Dosing
Adults
Standard: 1 DS tablet orally twice daily
Cellulitis
: 1-2 DS tablet orally twice daily
Dosing
Renal Insufficiency
Creatinine Clearance
: 15-30 ml/min
Decrease Trimethoprim-Sulfamethoxazole dose by 50%
Creatinine Clearance
: <15 ml/min
Avoid the use of Trimethoprim Sulfamethoxazole
References
Tarascon Pharmacopoeia, accessed online 8/8/2014
Dosing
HIV
Pneumocystis: PO or IV (15 mg/kg of trimethoprim/day)
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