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 symp toms. 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 infect ion may become infected, leading to conjunctivitis in 23% and pneumoni a in 21%. All of these sequelae of C. trachomatis infection may requir e in-or outpatient treatment. With >4 million infections estimated to occur each year in the US, C. trachomatis is one of the most common an d costly of the sexually transmitted pathogens. Treatment options for uncomplicated C. trachomatis infections in nonpregnant women include s ingle-dose azithromycin 1000mg or doxycycline 100mg twice daily for 7 days orally. In clinical trials, the bacteriological cure rate of sing le dose azithromycin 1000mg (95 to 100%) was similar to that of oral d oxycycline 200 mg/day for 7 days (88 to 100%) in nonpregnant women. Az ithromycin was at least as well tolerated as doxycycline and was assoc iated with mainly mild gastrointestinal adverse effects including diar rhoea, nausea and abdominal pain. Pharmacoeconomic analyses have sough t to determine if the 2.7- to 12-fold higher acquisition costs of azit hromycin in comparison with doxycycline are offset by its simple singl e-dose regimen which is likely to aid patient compliance and so optimi se drug efficacy. All analyses were retrospective cost-effectiveness d ecision-tree models and mainly considered direct costs. All models inc orporated an estimate of noncompliance with doxycycline and its influe nce on efficacy. For the treatment of confirmed C. trachomatis infecti on, azithromycin saved around $US1200 per major outcome avoided (1993 values; third-party payer perspective in the US) or US$3502 per case o f 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 resu lt was sensitive to changes of some parameters of the model. Azithromy cin was more costly than doxycycline from the perspective of a public health clinic which paid for the treatment of initial infection and ac ute sequelae only. Thus, pharmacoeconomic data from the US support the use of azithromycin in the treatment of nonpregnant women with confir med C. trachomatis urogenital infections from the perspective of the h ealthcare system or third-party payer; however, from the perspective o f a public clinic, doxycycline is the less costly option. Decreases in doxycycline compliance or azithromycin acquisition cost are factors t hat favour azithromycin.