title: Antacid attenuates the laxative action of magnesia in cancer patients receiving opioid analgesic.
abstract: OBJECTIVE
  This study was designed to investigate pharmacological interaction between magnesium laxative and antacid in patients receiving opioid analgesic.
  
  
  METHODS
  Data obtained from a total of 441 eligible patients receiving opioid analgesic for the first time were retrospectively analysed. The incidence of constipation, defined as stool-free interval of 3 days and more within the first week of opioid intake, was compared between patients who took laxative alone and those who received laxative in combination with antacid.
  
  
  RESULTS
  Laxatives were prescribed in 74% of patients, among them 61% received antacids such as proton pump inhibitor and H2 receptor blocker. Magnesia was the most commonly used laxative (89%). Constipation occurred in 21% and 55% of patients with and without laxatives, respectively. Antacids reversed the laxative action of lower doses (<2000 mg/day) but not higher doses (>2000 mg/day) of magnesia without affecting the effects of other laxatives. Therefore, it is suggested that both acid-dependent and acid-independent mechanisms may operate in the laxative action of magnesia, in which the former may be involved in the action of lower doses of magnesia.
  
  
  CONCLUSIONS
  Care should be taken to avoid the unfavourable pharmacological interaction between low doses of magnesia and antacid.
authors.affiliation: Department of Biomedical Informatics, Gifu University Graduate School of Medicine, Gifu, Japan.|Katorea Pharmacy, Gifu, Japan.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Ibuka
authors.affiliation: Department of Pharmacy, Gifu University Hospital, Gifu, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Ishihara
authors.affiliation: Department of Pharmacy, Gifu University Hospital, Gifu, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Suzuki
authors.affiliation: Department of Clinical Pharmaceutics, Meiji Pharmaceutical University, Tokyo, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Kagaya
authors.affiliation: Department of Gastroenterology, Gifu University Graduate School of Medicine, Gifu, Japan.
authors.forename: Masahito
authors.initials: M
authors.lastname: Shimizu
authors.affiliation: Department of Biomedical Informatics, Gifu University Graduate School of Medicine, Gifu, Japan.
authors.forename: Yasutomi
authors.initials: Y
authors.lastname: Kinosada
authors.affiliation: Department of Pharmacy, Gifu University Hospital, Gifu, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Itoh
mesh_terms: D000143:Acids / Q000378:metabolism; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000701:Analgesics, Opioid / Q000009:adverse effects*; D000863:Antacids / Q000009:adverse effects* / Q000627:therapeutic use; D000897:Anti-Ulcer Agents / Q000009:adverse effects / Q000627:therapeutic use; D003248:Constipation / Q000188:drug therapy* / Q000209:etiology; D004347:Drug Interactions; D006801:Humans; D054368:Laxatives / Q000008:administration & dosage / Q000494:pharmacology*; D008277:Magnesium Oxide / Q000008:administration & dosage / Q000494:pharmacology*; D008875:Middle Aged; D009369:Neoplasms / Q000188:drug therapy*; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D000143:Acids; D000701:Analgesics, Opioid; D000863:Antacids; D000897:Anti-Ulcer Agents; D054368:Laxatives; D008277:Magnesium Oxide
keywords: antacid; constipation; laxative; magnesia; opioid analgesic; pharmacological interaction