Azithromycin. A pharmacoeconomic review of its use as a single-dose regimen in the treatment of uncomplicated urogenital Chlamydia trachomatis infections in women.

In women, Chlamydia trachomatis infection often occurs in the urethra or cervix, with up to 70% of infections associated with few or no symptoms. Inadequate treatment may lead to infection of the upper genital tract and subsequent pelvic inflammatory disease (PID) in 10 to 40% of patients. PID causes an increased relative risk of ectopic pregnancy of 2.5 to 7.9 and PID may also lead to tubal infertility in about 17% of patients. 60% of infants born of mothers with C. trachomatis infection may become infected, leading to conjunctivitis in 23% and pneumonia in 21%. All of these sequelae of C. trachomatis infection may require in- or outpatient treatment. With > 4 million infections estimated to occur each year in the US, C. trachomatis is one of the most common and costly of the sexually transmitted pathogens. Treatment options for uncomplicated C. trachomatis infections in nonpregnant women include single-dose azithromycin 1000 mg or doxycycline 100 mg twice daily for 7 days orally. In clinical trials, the bacteriological cure rate of single dose azithromycin 1000 mg (95 to 100%) was similar to that of oral doxycycline 200 mg/day for 7 days (88 to 100%) in nonpregnant women. Azithromycin was at least as well tolerated as doxycycline and was associated with mainly mild gastrointestinal adverse effects including diarrhoea, nausea and abdominal pain. Pharmacoeconomic analyses have sought to determine if the 2.7- to 12-fold higher acquisition costs of azithromycin in comparison with doxycycline are offset by its simple single-dose regimen which is likely to aid patient compliance and so optimise drug efficacy. All analyses were retrospective cost-effectiveness decision-tree models and mainly considered direct costs. All models incorporated an estimate of noncompliance with doxycycline and its influence on efficacy. For the treatment of confirmed C. trachomatis infection, azithromycin saved around $US1200 per major outcome avoided (1993 values; third-party payer perspective in the US) or US$3502 per case of PID avoided (1993 values; US healthcare system perspective) compared with doxycycline. If infection was treated empirically, azithromycin was more costly than doxycycline by $US792 (1993 values), but the result was sensitive to changes of some parameters of the model. Azithromycin was more costly than doxycycline from the perspective of a public health clinic which paid for the treatment of initial infection and acute sequelae only. Thus, pharmacoeconomic data from the US support the use of azithromycin in the treatment of nonpregnant women with confirmed C. trachomatis urogenital infections from the perspective of the healthcare system or third-party payer; however, from the perspective of a public clinic, doxycycline is the less costly option. Decreases in doxycycline compliance or azithromycin acquisition cost are factors that favour azithromycin.