Drug General Information (ID: DDI1QG0YCT)
  Drug Name Allopurinol Drug Info Metolazone Drug Info
  Drug Type Small molecule Small molecule
  Therapeutic Class Antimetabolites Antihypertensive Agents
  Structure

 Mechanism of Allopurinol-Metolazone Interaction (Severity Level: Moderate)
     Increased risk of angioedema/anaphylactoid reactions Click to Show/Hide Mechanism Graph
Could Not Find 2D Structure
      Drug Name Allopurinol Metolazone
      Mechanism Hypersensitivity reactions Increase the risk of allopurinol-induced hypersensitivity reactions
      Key Mechanism Factor 1
Factor Name Angioedema/anaphylactoid reactions
Factor Description Anaphylactoid reaction is a condition in which symptoms similar to an allergic reaction occur, but no immune sensitization is detected. Most commonly, the syndrome begins with skin involvement, usually pruritus, flushing, urticaria, or angioedema. Angioedema is a reaction to a trigger that causes swelling of the tissue below the inner layer of the skin, called the dermis or submucosa, and the swelling can occur on the face, throat, or around the genitals.
      Mechanism Description
  • Increased risk of angioedema by the combination of Allopurinol and Metolazone 

Recommended Action
      Management Patients should be advised to promptly report any signs of hypersensitivity, including rash, pruritus, fever, or chills.

References
1 Mills RM "Severe hypersensitivity reactions associated with allopurinol." JAMA 216 (1971): 799-802
2 Hande KR "Evaluation of a thiazide-allopurinol drug interaction." Am J Med Sci 292 (1986): 213-6
3 Maschio G, Tessitore N, D'Angelo A, Fabris A, Pagano F, Tasca A, Graziani G, Aroldi A, Surian M, Colussi G, Mandressi A, Trinchieri ARocco F, Ponticel "Prevention of calcium nephrolithiasis with low-dose thiazide, amiloride and allopurinol." Am J Med 71 (1981): 623-6