Management of isopropyl nitrate-induced methaemoglobinaemia in pregnancy.

A pregnant female in her early 30s presented with cyanosis and oxygen saturation of 78%. She ingested isopropyl nitrate mistaking it for cannabidiol. Her arterial blood gas showed a methaemoglobin of >30% (outside the measuring range). She was treated with 120 mg of methylthioninium chloride (2 mg/kg) and symptoms improved. Her pregnancy progressed but was induced at 36 weeks because her child was small for gestational age. Methaemoglobinaemia is a rare presentation in pregnancy. There have been no reported cases of isopropyl nitrate-induced methaemoglobinaemia in pregnancy. Historically, intra-amniotic methylthioninium chloride was used in amniocentesis but use stopped after links to fetal malformations and neonatal death were made. There is no evidence outlining the risks of isopropyl nitrate in pregnancy and limited data on fetal effects from maternal exposure to intravenous methylthioninium chloride. This case adds to the evidence that treating methaemoglobinaemia may outweigh the risks of maternal exposure to methylthioninium chloride.

Interaction between methadone and clarithromycin as the suspected cause of an opioid toxidrome.

A 40-year-old patient was admitted through the acute medical take with pleuritic chest pain and rigours. He had a medical history of opiate dependence and was receiving 60 mg of methadone once daily. He was diagnosed with a community-acquired pneumonia and treated with amoxicillin and clarithromycin. After administration of only two concomitant doses of methadone and oral clarithromycin, he developed an opioid toxidrome with type-2 respiratory failure, a decreased level of consciousness and pinpoint pupils. The patient was treated with naloxone and his symptoms improved. Retrospectively, it was suspected that an interaction between clarithromycin and methadone might have contributed to the toxidrome. Respiratory failure has not been previously prescribed for this combination of medication and is of high importance for physicians and pharmacists around the world.