Background
Endometriosis is a chronic, recurring condition that occurs during the reproductive years. It is characterized by endometrial tissue developing outside the uterine cavity. This endometrial tissue development is dependent on estrogen produced primarily by the ovaries and, therefore, traditional management has focused on ovarian suppression. In this review we considered the role of modulation of the immune system as an alternative approach.

Objectives
To determine the effectiveness and safety of pentoxifylline, which has anti-inflammatory effects, in the management of endometriosis in subfertile, premenopausal women.

Search strategy
We searched the following databases (from inception to December 2008) for trials: Cochrane Menstrual Disorders and Subfertility Group Specialised Register, Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library), MEDLINE, EMBASE, CINAHL, and PsycINFO. In addition, all reference lists of included trials were searched and experts in the field were contacted in an attempt to locate trials.

Selection criteria
Randomised controlled trials (RCTs) comparing pentoxifylline with placebo or no treatment, medical treatment, or surgery in subfertile, premenopausal women were included.

Data collection and analysis
Two review authors independently selected trials for inclusion, assessed trial quality, and extracted data using data extraction forms. We contacted study authors for additional information and data. The domains assessed for risk of bias were sequence generation, allocation concealment, blinding, incomplete outcome data, and selective outcome reporting. Odds ratios (OR) were used for reporting dichotomous data with 95% confidence intervals (CI), whilst mean differences (MD) were expressed for continuous data. Statistical heterogeneity was assessed using the I2 statistic.

Main results
Four trials involving 334 participants were included. Results showed pentoxifylline had no significant effect on reduction in pain (one RCT, MD -1.60, 95% CI -3.32 to 0.12). There was no evidence of an increase in clinical pregnancy events in the pentoxifylline group compared with placebo (three RCTs, OR 1.54, 95% CI 0.89 to 266). For recurrence of endometriosis, one RCT reported an OR of 0.88 (95% CI 0.27 to 2.84). No trials reported the effects of pentoxifylline on the odds of live birth rate per woman, improvement of endometriosis-related symptoms, or adverse events.

Authors' conclusions
There is not enough evidence to support the use of pentoxifylline in the management of premenopausal women with endometriosis in terms of subfertility and relief of pain outcomes.