ASK DIS: Tissue Penetration of Oral Bactrim

Bactrim is rapidly absorbed following oral administration (85%)
Peak blood levels for the individual components occur 1 to 4 hours after oral administration. The mean serum half-lives of sulfamethoxazole and trimethoprim are 10 and 8 to 10 hours, respectively
Both sulfamethoxazole and trimethoprim distribute to sputum, vaginal fluid and middle ear fluid
Average percentage of the dose recovered in urine from 0 to 72 hours after a single oral dose of sulfamethoxazole and trimethoprim is 84.5% for total sulfonamide and 66.8% for free trimethoprim
trimethoprim also distributes to bronchial secretion
both pass the placental barrier and are excreted in human milk.

Skin and Tissue Penetration

Good penetration and are indicated for treatment of several infections
pharmacokinetic/pharmacodynamic study found that trimethoprim/sulfamethoxazole exhibits good skin/soft tissue penetration in patients with Diabetic foot ulcers as well as bactericidal activity in serum against strains of S. aureus and β-haemolytic streptococci
Oral options for treatment of gram-negative (osteomyelitis) infections include fluoroquinolones and trimethoprim-sulfamethoxazole
Has excellent oral bioavailability that has been used to treat MSSA and MRSA bone infections, though most of the published experience is with courses of longer than 6 weeks and in device-associated infections.
Optimal dosing should be weight based: 5 to 10 mg/kg of trimethoprim/day divided into 2 or 3 doses in individuals with normal renal function

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ASK DIS