High-dose oral antibiotic therapy has demonstrated adequate bactericidal activity in bone and joint tissue in children, allowing the option of oral antibiotic therapy in the convalescent phase of treatment for bacterial arthritis. Newton and associates compared the effectiveness of convalescent high-dose oral antibiotic therapy with intravenous therapy for septic arthritis in patients 16 years of age or younger.

The study included 186 children who received treatment at two medical centers; 83 children were seen at one hospital and 103 at the other hospital. The diagnosis of septic arthritis was confirmed by joint fluid that showed positive Gram stain or culture, more than 20,000 white blood cells per mm³, or gross purulence. Most of the patients had infection of the knee or hip, with staphylococcal or streptococcal infection being most common.

The 83 children at one hospital were given high-dose oral antibiotic therapy after approximately one week of intravenous therapy. The 103 children at the other hospital were switched to high-dose oral antibiotic therapy after two weeks of parenteral antibiotic therapy.

Cefazolin was the most commonly used intravenous antibiotic. Oral therapy for staphylococcal infection consisted of cephalexin or cloxacillin, in a dosage of 100 to 150 mg per kg per day, or dicloxacillin, in a dosage of 75 to 100 mg per kg per day, divided into four daily doses. For streptococcal or pneumococcal infections, oral penicillin V or amoxicillin, in a dosage of 75 to 100 mg per kg per day, was used.

Serum bactericidal levels were determined in children with staphylococcal infection after the second or third oral dose. If the titer was less than 1:8, the oral dosage was increased to a maximum of 150 mg per kg per day, and testing was repeated to ensure that the titer was 1:4 to 1:8. No patient required reinstitution of intravenous therapy. Total duration of therapy was 30.1 days at one site and 28 days at the other. The complication rate was minimal.

The authors conclude that oral high-dose antibiotic therapy is effective in children with septic arthritis who have responded well to an initial course of intravenous antibiotic therapy. Compliance with the administration of oral medication must be certain. In addition, an adequate serum bactericidal titer must be confirmed shortly after initiation of oral therapy for staphylococcal infection because of varying sensitivities of this organism.