title: Synergistic relaxing effect of the paracetamol and pyrilamine combination in isolated human myometrium.
abstract: OBJECTIVE
  To evaluate the interaction type of the human uterine relaxant effect of the paracetamol-pyrilamine combination (PPC) in vitro.
  
  
  METHODS
  Uterine strips were contracted with KCl (60 mM) and treated with vehicle or increasing concentrations of paracetamol (100-3200 μM), pyrilamine (3.2-100 μM) or the PPC. The relaxing effects of the drugs alone and in combination were measured. Isobolographic analysis was used to determine the pharmacologic interaction type.
  
  
  RESULTS
  Paracetamol, pyrilamine and the PPC produced a significant relaxing effect on non-pregnant human uterine strips pre-contracted with KCl (60 mM). The EC30 values for paracetamol and pyrilamine on the uterine contraction were 2391.3±595.3 μM and 14.7±1.7 μM, respectively. The derived experimental EC30 for the PPC was 401.8±129.8 μM. This value was significantly lower (p<0.05) than the theoretical EC30 expected for a purely additive interaction, which was 1203.0±297.7 μM for the PPC. The interaction index (γ) was 0.33±0.14 for PPC, being statistically different from unity.
  
  
  CONCLUSIONS
  Data suggest that low doses of the PPC can interact synergistically and therefore this drug association may represent a therapeutic advantage for the clinical treatment of dysmenorreic pain.
authors: Área Académica de Medicina del Instituto de Ciencias de la Salud, Universidad Autónoma del Estado de Hidalgo, and Hospital General de los SSH, Pachuca, Hidalgo, Mexico. mario_i_ortiz@hotmail.com
authors: Mario I
authors: MI
authors: Ortiz
authors: Héctor A
authors: HA
authors: Ponce-Monter
authors: José A
authors: JA
authors: Mora-Rodríguez
authors: Guillermo
authors: G
authors: Barragán-Ramírez
authors: Bertha S
authors: BS
authors: Barrón-Guerrero
mesh_terms: D000082:Acetaminophen / Q000494:pharmacology*; D000328:Adult; D018712:Analgesics, Non-Narcotic / Q000494:pharmacology*; D003627:Data Interpretation, Statistical; D004357:Drug Synergism; D004412:Dysmenorrhea / Q000188:drug therapy; D005260:Female; D006634:Histamine H1 Antagonists / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D008875:Middle Aged; D009126:Muscle Relaxation / Q000187:drug effects*; D009215:Myometrium / Q000187:drug effects*; D009467:Neuromuscular Depolarizing Agents / Q000494:pharmacology; D009994:Osmolar Concentration; D011189:Potassium Chloride / Q000494:pharmacology; D011738:Pyrilamine / Q000494:pharmacology*; D014590:Uterine Contraction / Q000187:drug effects; D055815:Young Adult
chemical_list: D018712:Analgesics, Non-Narcotic; D006634:Histamine H1 Antagonists; D009467:Neuromuscular Depolarizing Agents; D000082:Acetaminophen; D011189:Potassium Chloride; D011738:Pyrilamine