Treatment of Cellulitis with Trimethoprim-Sulfamethoxazole

Dosage for Adults

The American College of Physicians recommends a dosage of 3.5-4.0 mg/kg/dose of the trimethoprim component every 8-12 hours for complicated skin and soft tissue infections, such as cellulitis, in adults 1
The Infectious Diseases Society of America suggests that this dosage is particularly important in cases of complicated cellulitis that require hospitalization or when there are signs of systemic infection 1, 2
For patients with systemic toxicity and/or rapidly progressive or worsening infection despite appropriate oral antibiotics, hospital management with intravenous antibiotics is recommended 2

The Centers for Disease Control and Prevention note that TMP-SMX has good in vitro activity against community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA), but its activity against beta-hemolytic streptococci is not well defined 2
In cases of non-purulent cellulitis, where beta-hemolytic streptococci are the most likely pathogens, consideration of an alternative agent or combination therapy is recommended 2

The American Academy of Pediatrics recommends a dosage of 15-20 mg/kg/day of the trimethoprim component (75-100 mg/kg of the sulfamethoxazole component) administered intravenously in 3-4 divided doses for children over 2 months with severe infections such as Pneumocystis jiroveci pneumonia 3
For central nervous system infections in children, the recommended dosage is 5 mg/kg/dose of the trimethoprim component intravenously every 8-12 hours 4

The Infectious Diseases Society of America states that the duration of therapy for skin and soft tissue infections has not been well defined, although no differences in outcome were observed between adult patients with uncomplicated cellulitis who received 5 versus 10 days of therapy 4
In FDA licensure trials for complicated skin and soft tissue infections, patients were typically treated for 7-14 days 4
The duration of treatment should be individualized based on the patient's clinical response 4

The Centers for Disease Control and Prevention recommend regular monitoring of complete blood counts during TMP-SMX therapy 3
Common adverse effects include skin rash, neutropenia, thrombocytopenia, and elevated liver enzymes 3
For mild or moderate skin reactions, TMP-SMX may be temporarily discontinued and restarted when the rash has resolved 3
If a urticarial rash or Stevens-Johnson syndrome occurs, TMP-SMX should be discontinued and not readministered 3