Metamizole and agranulocytosis

Metamizole and agranulocytosis

Due to very rare but serious adverse drug reactions, according to the Swiss Information for healthcare professionals, metamizole should only be used in cases of severe pain and fever that do not respond to other measures.

Key words: Novalgin, metamizole, agranulocytosis

Incident data


Year: 2018

Age: 34 years

Sex: Male

Medicinal product: Novalgin®

Active substances: Metamizole

Indication: postoperative analgesia

ADR: Agranulocytosis

Outcome: recovering

Around two weeks after L4-L5 microsurgical decompression, the patient was referred as an emergency with severe streptococcus A tonsillitis. Laboratory tests found agranulocytosis (neutrophils 0.3 G/l; reference: 1.40- 8.00 G/l). Oral intake was also difficult due to significant oropharyngeal swelling, resulting in intravenous fluid and electrolyte replacement being required. A neck CT found tonsillar hypertrophy with cervical lymphadenopathy without indication of malignancy. Novalgin® was stopped due to a suspected adverse drug reaction. Triple antibiotic treatment and prophylactic antiviral and antimycotic treatment were started. The granulocyte count recovered following two doses of filgrastim.

Year: 2020

Age: 22

Sex: Male

Medicinal product: Novalgin

Active substance: Metamizole

Indication: Pain following multiple injuries from a traffic accident

ADR: Agranulocytosis

Outcome: fatal

Following multiple injuries in a traffic accident on 31 July 2019, the patient took 4 x 500 mg Novalgin® (metamizole) daily for a number of weeks. In the weeks prior to hospitalisation, he had been taking Novalgin® as required for headaches. The patient was admitted to hospital as an emergency due to appendicitis with the onset of septic shock. Laboratory tests found agranulocytosis (neutrophils: 0.03 G/l (reference: 1.40- 8.00 G/l). Filgrastim was therefore administered. The patient subsequently developed severe ARDS secondary to invasive aspergillosis. Severe pancytopenia showed no regeneration in bone marrow aspirations. The respiratory situation deteriorated further. The patient also developed abdominal compartment syndrome in neutropenic enterocolitis. Despite maximum intensive medical support, the patient died one month after his initial presentation in the emergency department.

Summary and recommendation

Agranulocytosis is a known, very rare (<1/10,000) adverse drug reaction to metamizole, including cases with a fatal outcome. Typical signs include inflamed mucosal lesions (e.g. oropharyngeal, anorectal, genital), sore throat and fever. The typical signs may also be minimal in patients receiving antibiotic treatment.

Agranulocytosis induced by metamizole is an allergic immune reaction that lasts for at least one week. The reaction has no connection to the dose administered and can occur at any time during the treatment. All patients treated with metamizole must be instructed to contact a doctor immediately if they develop signs and symptoms that could indicate a blood dyscrasia, e.g. feeling generally ill, sore throat, signs of infection, persistent fever, haematoma, bleeding or paleness.

Treatment should be discontinued immediately in case of a blood dyscrasia. Regular checks must be performed until values have returned to normal.

Healthcare professionals are requested to report serious and/or previously unknown adverse drug reactions to Swissmedic. Please use the Electronic Vigilance Reporting Portal “ElViS” for this purpose.