title: Dynamics and significance of placebo response in primary dysmenorrhea.
abstract: A total of 55 patients with primary dysmenorrhea who had shown a favorable response to a preliminary treatment cycle with placebo were admitted to a double-blind study on placebo versus antiprostaglandin agents (naproxen and pirprofen). To evaluate the placebo effect and its duration, the treatment was given for 4 successive cycles. Whereas the antiprostaglandin agents were effective in most of the patients (in 80% of the pirprofen group and 85.7% of the naproxen group) and this efficacy was maintained throughout the study, a favorable response to placebo was observed in 84% in the first cycle, 29% in the second, 16% in the third and 10% in the fourth. The incidence of side effects was similar in the placebo and the active treatment groups (35.4% vs. 37.5%). It is postulated that a placebo effect in dysmenorrhea is due to a central analgesic mechanism mediated by endorphin release or possibly to psychological dynamics (mental or conditioning theories). However, this effect loses efficacy with time possibly due to a decreased susceptibility to the opioid action of the central nervous circuits responsible for menstrual pain perception or to deconditioning mechanisms.
authors.affiliation: 1st Department of Obstetrics and Gynecology, University of Milan, MilanItaly Department of Physiopathology and Pain Therapy, University of Milan, MilanItaly.
authors.forename: Luigi
authors.initials: L
authors.lastname: Fedele
authors.forename: Maurizio
authors.initials: M
authors.lastname: Marchini
authors.forename: Barbara
authors.initials: B
authors.lastname: Acaia
authors.forename: Ubaldo
authors.initials: U
authors.lastname: Garagiola
authors.forename: Mario
authors.initials: M
authors.lastname: Tiengo
mesh_terms: D000328:Adult; D004311:Double-Blind Method; D004412:Dysmenorrhea / Q000188:drug therapy / Q000523:psychology*; D005260:Female; D006801:Humans; D009288:Naproxen / Q000009:adverse effects / Q000627:therapeutic use*; D010666:Phenylpropionates / Q000009:adverse effects / Q000627:therapeutic use*; D010919:Placebos
chemical_list: D010666:Phenylpropionates; D010919:Placebos; D009288:Naproxen; C008924:pirprofen