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ADVERSE EFFECTS

Known allergy to chlorhexidine:

COMMON STEM -grel

NN A drug’s real name

a preventable death The Netherlands Pharmacovigilance Centre (Lareb) has received a case report of anaphylactic shock in an elderly patient, which occurred 10 minutes after the product Instillagel° was used for inserting a urinary catheter. This brand name does not indicate that this urethral gel contains chlorhexidine , an antiseptic, plus lidocaine , a local anaesthetic. The patient was known to have an allergy to chlorhexidine . He was resuscitated, but he died 2months later from the consequences of anaphylactic shock (1). Analysis of this event by the healthcare team and the Dutch Institute for prevention of medication incidents identified, among the contributory factors, lack of awareness that this patient might have chlorhexidine allergy and a lack of knowledge of the substances contained in drugs and medical devices that can cause allergic reactions (1). Hypersensitivity reactions, including sometimes fatal ana phylaxis, had already been reported with chlorhexidine (2,3). Patients and healthcare workers have frequent contact with this substance (sometimes leading to sensitisation), due to its presence in many products in everyday use, e.g. topical medi cines, mouthwash, dressings and tubes. After a first allergic episode, further exposure is therefore difficult to avoid. In many situations, it is not known that this antiseptic is present, and the value of using it has not been demonstrated (1-5). IN PRACTICE  Chlorhexidine is an allergen. Allergy to chlor hexidine should be considered whenever an allergic-type re action occurs that is associated with a healthcare procedure in which it has been used. It is important that patients (and their family and friends) familiarise themselves with this information, and that it is recorded in their medical records. When prescribing, dispensing or administering a product containing chlorhexidine, it is essential to check with the patient that they are not allergic to it, if necessary by looking in their medical records. If there is a known allergy, it is important to read the composition of the product. ©Prescrire References 1- Instituut Verantwoord Medicijngebruik - Voorkomen Medicatie-­ Incidenten “Praktijkprikkel Anafylaxie bij bekende chloorhexidineallergie” Praktijk prikkel 2022; (8): 2 pages. 2- Prescrire Editorial Staff “Chlorhexidine: anaphylaxis following skin application” Prescrire Int 2017; 26 (188): 296. 3- Opstrup MS et al. “Chlorhexidine allergy: On the rise and often overlooked” Curr Allergy Asthma Rep 2019; 19 (5): 23. 4- Prescrire Rédaction “Exposition professionnelle des soignants aux médicaments: bilan des notifications en France de 2009 à 2019” Rev Prescrire 2022; 42 (460): 111-112. 5- Prescrire Rédaction “Lidocaïne + chlorhexidine en gel urétral (Instillagel°). Des risques mais pas d’avantage en termes d’efficacité” Rev Prescrire 2003; 23 (239): 337-338. ▶ Translated from Rev Prescrire January 2023 Volume 43 N° 471 • Page 25

According to the nomenclature for international non-proprietary

names (INNs) established by theWorld Health Organization (WHO), the INNs of antiplatelet drugs contain, or end in, the common stem -grel (1). As of 26 October 2022, we have identified 5 drugs whose INN contains this stem: ana grelide (Xagrid° or other brands), which also has a platelet-lowering action, used in some patients with essential thrombocythemia (see “Anagrelide: thrombosis following discon tinuation” Prescrire Int n° 246); clopidogrel used for prevention of ischaemic events and, in combination with aspirin , after certain acute coronary events; and cangrelor (Ken grexal°), prasugrel (Efient° or other brands) and ticagrelor (Brilique°) also used, in com bination with aspirin , after some acute cor onary events (1). The INNs of some older antiplatelet drugs do not contain this common stem, resulting in exceptions to the rule: for example aspirin , ticlopidine and dipyridamole (1). All the antiplatelet drugs carry a risk of haemorrhage. This risk is increased when they are combined with another drug that can lead to bleeding, such as a nonsteroidal anti-inflammatory drug or an anticoagu lant (2). ©Prescrire

▶ Translated from Rev Prescrire December 2022 Volume 42 N° 470 • Page 899

References 1- World Health Organization “The use of stems in the selection of International Nonproprietary Names (INN) for pharma ceutical substances 2018 (Stem Book 2018)”: 105. 2- “Clopidogrel, prasugrel et ticlopidine” + “Dipyridamole” + “Ticagrélor et cangrélor” Interactions Médicamenteuses Prescrire 2023.

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Prescrire Int • April 202 3

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