Deliberate Metformin Overdose: Unveiling the Perils of Lactic Acidosis

Introduction:

Metformin, a cornerstone in the treatment of type 2 diabetes mellitus, is generally safe and well-tolerated when used appropriately. However, deliberate overdose of metformin can lead to severe toxicity, primarily manifesting as lactic acidosis. This clinical story highlights the symptoms and treatment of a deliberate metformin overdose, emphasizing the importance of early recognition and management of lactic acidosis over hypoglycaemia.

Case Presentation:

John, a 38-year-old man with a history of depression and type 2 diabetes, was found in a state of distress with an empty bottle of metformin tablets beside him. He had intentionally ingested an excessive amount of metformin in an impulsive act. He was rushed to the emergency department, where the healthcare team promptly assessed his condition and initiated appropriate interventions.

Symptoms: In deliberate metformin overdose, the symptoms primarily revolve around the development of lactic acidosis, which occurs due to impaired metabolism and clearance of metformin by the liver. The following symptoms were observed in John’s case:

Gastrointestinal Distress: John experienced severe nausea, vomiting, and abdominal pain. These symptoms were attributed to the direct irritant effect of metformin on the gastrointestinal tract.
Profound Lethargy and Weakness: Lactic acidosis compromises cellular energy production, resulting in fatigue, profound weakness, and general malaise. John’s physical and mental capacities were significantly impaired.
Kussmaul Respirations: As lactic acidosis progressed, John exhibited rapid, deep breathing (Kussmaul respirations) as his body attempted to compensate for the acid-base imbalance.
Hypotension and Tachycardia: Lactic acidosis can impair cardiovascular function, leading to hypotension (low blood pressure) and tachycardia (rapid heart rate).
Altered Mental Status: As lactic acidosis worsened, John experienced confusion, disorientation, and decreased level of consciousness.
Treatment: The treatment of deliberate metformin overdose focuses on managing the lactic acidosis and its associated complications. The medical team employed the following strategies:

Gastric Lavage and Activated Charcoal: Given the intentional overdose, gastric lavage was performed to remove any remaining metformin from John’s stomach. Activated charcoal was also administered to adsorb any residual metformin in the gastrointestinal tract, limiting its absorption into the bloodstream.
Fluid Resuscitation: Intravenous fluids, particularly isotonic saline, were administered to correct dehydration, restore hemodynamic stability, and enhance metformin elimination.
Haemodialysis: Due to the severity of the overdose and the potential for refractory lactic acidosis, John underwent emergency haemodialysis. Haemodialysis acts as an extracorporeal method of removing metformin and correcting lactic acidosis by enhancing drug elimination.
Bicarbonate Therapy: Sodium bicarbonate was administered intravenously to correct acidosis and maintain appropriate pH levels. However, it is important to note that bicarbonate therapy is controversial and should be used judiciously, as it may exacerbate underlying lactate production.
Supportive Care: John received meticulous monitoring of vital signs, electrolyte levels, and blood gases. Close attention was paid to his mental status, ensuring appropriate supportive care and safety measures were implemented.
Outcome: Despite the grave initial presentation, early recognition and aggressive management of lactic acidosis resulted in a gradual improvement of John’s condition. Haemodialysis effectively removed excess metformin and corrected the lactic acidosis. Throughout his hospital stay, John received psychiatric evaluation and counselling to address the underlying issues that led to the deliberate overdose.

Conclusion: Deliberate metformin overdose represents a critical medical emergency with potentially life-threatening consequences. This case emphasizes the significance of recognizing the predominant complication of lactic acidosis rather than focusing solely on hypoglycaemia. Prompt medical intervention, including supportive care, haemodialysis, and bicarbonate therapy, plays a crucial role in mitigating the effects of metformin overdose and improving patient outcomes.

References:

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Author : James Bingham | BSc (Hons) Paramedic Practitioner MCPara | Paramedic