Metformin (Glucophage) - Uses, Side Effects

Glucophage Overdose & Missed Dose

Clinical Presentation of Toxicity

Time Course of Symptoms

Time Post-Ingestion Expected Symptoms Pathophysiology
0-6 hours Nausea, vomiting, diarrhea Gastrointestinal irritation
6-12 hours Hyperventilation, tachycardia Compensated metabolic acidosis
>12 hours Hypotension, hypothermia, coma Profound lactic acidosis (pH <7.0)

Laboratory Findings

  • Arterial blood gas: pH <7.2, HCO3 <10 mEq/L
  • Lactate levels: >5 mmol/L (often 15-25 mmol/L)
  • Metformin levels: >5 μg/mL (therapeutic range 1-2 μg/mL)

Emergency Treatment Protocol

1. Gastrointestinal Decontamination

Intervention Time Window Efficacy
Activated charcoal <1 hour post-ingestion Limited benefit (poor adsorption)
Whole bowel irrigation <4 hours for XR formulations Consider for massive ingestions

2. Lactic Acidosis Reversal

  1. IV sodium bicarbonate: Target pH >7.1 (50-100 mEq boluses)
  2. Mechanical ventilation: For respiratory compensation
  3. Vasopressors: Norepinephrine for refractory hypotension

3. Hemodialysis Criteria

  • pH <7.0 refractory to bicarbonate
  • Lactate >20 mmol/L
  • Renal failure (creatinine >2.5 mg/dL)
  • Metformin level >50 μg/mL

Protocol: 4-hour sessions with high-flux membrane

Missed Dose Management

Standard Recommendations

  • If <6 hours late: Take missed dose immediately
  • If >6 hours late: Skip dose, resume normal schedule
  • Never double dose: Risk of GI symptoms increases 3-fold

High-Risk Patient Considerations

Patient Type Action
Renal impairment (eGFR 30-60) Check glucose before resuming
Post-operative Wait until oral intake tolerated