RESUMO
Introduction: Promethazine is a phenothiazine derivative that possesses antihistamine, anti-dopaminergic and anticholinergic properties. It is commonly used to treat motion sickness, allergic conditions, nausea and vomiting, in addition to its use as a sedative. Promethazine has vesicant properties and is highly caustic to the intima of blood vessels and surrounding tissues. Intravenous administration may result in thrombophlebitis, unintentional intra-arterial administration, perivascular extravasation and tissue necrosis. To the best of our knowledge there is no previous published report of promethazine-induced thrombophlebitis from sub- Saharan Africa. Case Report: A 29-year-old Nigerian male was admitted at our hospital on account of malaria with acute gastroenteritis. Due to persistent vomiting, he was administered 25 mg of promethazine injection via a size 22G intravenous cannula which was inserted the previous day on the anteromedial aspect of his right forearm and maintained with continuous intravenous crystalloid infusion. Upon administration of promethazine, he experienced intense burning and erythema. The cannula was removed immediately, another cannula was inserted on the contralateral arm, and promethazine was replaced with ondansetron. Subsequently, he developed a tender, subcutaneous cord-like swelling extending from the middle-third of the anteromedial aspect of his right forearm, corresponding with the site of previous venous cannulation. Ultrasonography revealed a hypoechoic, non-compressible basilic vein, with no flow on colour Doppler interrogation, in keeping with superficial thrombophlebitis. He was treated with a topical anti-inflammatory agent, and the pain and redness subsided after four weeks. Conclusion: The preferred parenteral route of administration of promethazine is deep intramuscular injection. Recommendations to prevent promethazine-induced thrombophlebitis include: use of large and patent veins, use of lower doses, drug dilution and slow administration, use of alternative therapies, and patient education. Promethazine-induced tissue injury is under-reported in this part of the world. Creating awareness through this case report would help reduce the morbidity following promethazine administration.
