Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.
The safety of methylene blue in adults with acquired methemoglobinemia was assessed in 24 patients who received at least 1 dose of methylene blue [
see Clinical Studies (
14)
]. Most doses administered were 1 mg/kg (88.5%), but doses from 1 mg/kg to 2 mg/kg were administered. All patients received at least one dose of methylene blue; two received two doses. Serious adverse reactions occurred in 4.2% of patients who received methylene blue. A serious adverse reaction of seizure-like phenomenon was reported in one patient. Adverse reactions (≥2%) included headache, hypokalemia, diarrhea, hypomagnesemia, myoclonus, nausea, and seizure-like phenomena.
The safety of methylene blue in pediatric patients with acquired methemoglobinemia was assessed in two retrospective case series that included two pediatric patients treated with methylene blue and 12 treated with another methylene blue product. The case series included patients in the following age groups: 3 neonates (<1 month), 4 infants (1 month to <2 years), 4 children (2 years to <12 years), and 3 adolescents (12 years to <17 years). The safety profile in pediatric patients was similar to that in adult patients.
Other adverse reactions reported to occur following administration of methylene blue class products include the following:
Blood and lymphatic system disorders: hemolytic anemia, hemolysis, hyperbilirubinemia
Cardiac disorders: palpitations, tachycardia
Eye disorders: eye pruritus, ocular hyperemia, vision blurred
Gastrointestinal disorders: abdominal pain lower, dry mouth, flatulence, glossodynia, tongue eruption
General disorders and administration site conditions: death, infusion site extravasation, infusion site induration, infusion site pruritus, infusion site swelling, infusion site urticaria, peripheral swelling, thirst
Investigations: elevated liver enzymes
Musculoskeletal and connective tissue disorders: myalgia Renal and urinary disorders: dysuria
Respiratory, thoracic and mediastinal disorders: nasal congestion, oropharyngeal pain, rhinorrhea, sneezing Skin and subcutaneous tissue disorders: necrotic ulcer, papule, phototoxicity Vascular disorders: hypertension