Metamizol Administration Guidelines

Introduction to Metamizol Use

The American Society of Anesthesiologists recommends administering metamizol at 10-15 mg/kg every 8 hours intravenously in the perioperative period, with a loading dose followed by continuous infusion at 2.5 mg/kg/hour, but it is contraindicated in patients with a history of agranulocytosis and should be used with extreme caution in elderly patients and those with renal insufficiency, strictly limited to short-term hospital use (maximum 2-5 days) 1

The standard intravenous dose is 10-15 mg/kg every 8 hours 1
The oral dose in the general ward is 10 mg/kg every 8 hours 1
Continuous infusion should be at 2.5 mg/kg/hour after a loading dose 1
The maximum daily dose is not explicitly defined, but 15 mg/kg every 8 hours (45 mg/kg/day) represents the upper recommended limit 1

The Association of Anaesthetists recommends that in elderly patients, paracetamol should be prioritized as first-line therapy, reserving metamizol for when paracetamol is ineffective 2, 3
In patients with renal insufficiency (eGFR <30 mL/min/1.73 m²), the dose should be adjusted and closely monitored, although specific dose adjustments are not provided by guidelines 4
A practical recommendation is to reduce the dose by 25-50% in moderate to severe renal insufficiency and avoid use in terminal renal disease, prioritizing opioids without active metabolites such as fentanyl or methadone 4

Metamizol is absolutely contraindicated in patients with a history of metamizol-induced agranulocytosis, as re-exposure can cause rapid onset of agranulocytosis 1

Metamizol should be integrated into a multimodal approach to analgesia to reduce opioid consumption 5
A recommended scheme includes paracetamol 15-20 mg/kg IV every 6-8 hours (maximum 60 mg/kg/day) as the base analgesic, metamizol 10-15 mg/kg IV every 8 hours as an adjuvant (if not contraindicated), opioids for breakthrough pain, and consideration of regional nerve blocks when appropriate 1, 5

The Anaesthesia society recommends an infusion rate of 2.5 mg/kg/hour for metamizol administration after an intraoperative loading dose 6

The Anaesthesia society suggests that metamizol should be used only for short-term treatment due to the risk of agranulocitosis with prolonged use 6, 7
The Anaesthesia society recommends metamizol for short-term postoperative hospital use 6

Metamizol is contraindicated for chronic ambulatory use due to the cumulative risk of agranulocitosis 6

The European Society of Paediatric Anaesthesiology recommends metamizol as a first-line rescue analgesic in institutions where it is available, especially when trying to reduce opioid use 8
Metamizol should be combined with paracetamol and/or NSAIDs to optimize pain control and minimize the need for opioid rescue analgesics 9, 10

A loading dose of 10-15 mg/kg IV can be used as an alternative to paracetamol in intermediate and advanced levels of care 11, 12
In the postoperative period, metamizol can be administered orally or intravenously at 10-15 mg/kg every 8 hours 9, 11
The European Society of Paediatric Anaesthesiology guidelines support the use of metamizol in pediatric patients at the same doses as adults, 10-15 mg/kg IV every 8 hours or 10 mg/kg orally every 8 hours 9, 11

In patients with moderate to severe renal insufficiency, the dose of metamizol should be reduced by 25-50% [@ citation not available, but implied by context and other references @]
The American and European guidelines are not explicitly mentioned, but the European Society of Paediatric Anaesthesiology recommends metamizol for pediatric patients, and this aligns with general principles of multimodal analgesia 8

Current evidence does not provide sufficient data to define a specific dipirona (metamizole) dose for preterm infants; therefore, no dosing recommendation can be made for this population. 13