Single-dose therapy of infectious diseases.

Single-dose antimicrobial therapy has clear advantages over multiple-dose therapy. Long-acting penicillins have been used for many years in single doses for treatment of streptococcal pharyngitis and early syphilis. More recently, shorter-acting agents are used for non-invasive mucosal infections. In trichomonas vaginitis, for instance, a 2g single dose of metronidazole is approximately 92% effective and is considered the treatment of choice. Controversy still exists about the value of single-dose therapy in women who have bacterial cystitis. However, there is good evidence that 2 or 3 double-strength tablets of co-trimoxazole are very effective and safe in the treatment of uncomplicated cystitis in healthy women.