Drug-induced methaemoglobinaemia. Treatment issues

Area of Science:

• Hematology
• Toxicology
• Pharmacology

Background:

• Erythrocytes normally maintain low methaemoglobin levels via the NADH diaphorase system.
• Methaemoglobinaemia arises from xenobiotics that oxidize hemoglobin directly or after metabolic activation.
• Clinically significant methaemoglobin inducers include local anesthetics (benzocaine, prilocaine), nitrites, dapsone, and primaquine.

Purpose of the Study:

• To review the pathophysiology, clinical manifestations, diagnosis, and treatment of methaemoglobinaemia.
• To highlight the role of xenobiotics in causing methaemoglobinaemia.
• To emphasize the importance of physician awareness for prompt management.

Main Methods:

• Review of existing literature on methaemoglobinaemia.
• Analysis of clinical consequences based on methaemoglobin blood levels.
• Discussion of diagnostic tools (CO-oximeter) and limitations (pulse oximeters).
• Outline of treatment strategies including methylene blue, exchange transfusion, and cimetidine.

Main Results:

• Clinical symptoms correlate with methaemoglobin levels, ranging from dyspnea to coma and fatality.
• Cyanosis unresponsive to oxygen suggests methaemoglobinaemia.
• Intravenous methylene blue is the primary treatment; alternative strategies are needed for non-responders or specific deficiencies (G6PD).

Conclusions:

• Methaemoglobinaemia is a potentially life-threatening condition requiring accurate diagnosis and timely intervention.
• Increased physician awareness of drug-induced methaemoglobinaemia is essential for effective patient outcomes.
• Understanding the mechanisms and management of methaemoglobinaemia improves patient care.