Menstrual cycle length during methadone maintenance

Aims: While the menstrual disruption of heroin has been demonstrated, there are few published data concerning methadone maintenance and menstrual function. This study was conducted to evaluate whether cycle length was more regular during methadone maintenance. Settings: An out-patient research treatment program in Baltimore, Maryland, USA. Participants: A total of 191 heroin and cocaine-using women from two clinical trials, lasting 25-29 weeks; each woman was maintained on 70-100 mg of methadone. Measurements: Start/end dates of each menses were collected. Design: Menstrual patterns were classified as regular, irregular, transient amenorrhea, persistent amenorrhea or cycle restart. Repeated-measures regression modeling determined correlates of cycle length and predictors of long cycles (> 40 days) and short cycles (< 20 days). Bleeding episodes were defined as 1 or more bleeding days, bound by at least 2 non-bleeding days. Correlates/predictors examined were body mass index, drug use, methadone dose and race. Findings: In the 133 women for whom menstrual patterns could be determined, cycle-length irregularity was common: irregular, 62 (46.7%); regular, 37 (27.8%); cycle restart, 16 (12%); persistent amenorrhea, 11 (8.3%); transient amenorrhea, seven (5.3%). Each additional week on methadone maintenance was associated with decreased risk of long (OR = 0.96, P < 0.01 and short (OR = 0.92, P < 0.01) cycles. Of 27 women with secondary amenorrhea pre-study, 16 (59%) restarted menses. Positivity for opioids or cocaine was not significantly associated with short or long cycles. Conclusions: Cycle length begins to normalize during methadone maintenance. Menses resumption may occur. Methadone maintenance, despite interfering with menstrual function in an absolute sense, may interfere less than illicit heroin abuse.