Starting on June 22, 2023, all medications containing pholcodine were withdrawn in Singapore. This decision was made by the Health Sciences Authority (HSA) in consultation with its Product Vigilance Advisory Committee because the benefits of using pholcodine to treat non-productive cough did not outweigh the potential risk of perioperative anaphylaxis (POA) when used with neuromuscular blocking agents (NMBAs). The company responsible for these products canceled their registrations and ceased their distribution in June 2023.
The decision was based on findings from the Allergy to Neuromuscular Blocking Agents and Pholcodine Exposure (ALPHO) study, which showed an association between pholcodine use and NMBA-related POA. Pholcodine is believed to sensitize individuals to NMBAs, potentially leading to POA. However, there are no reliable tests to predict which pholcodine-exposed patients are at high risk of developing POA to NMBAs. Multiple international regulatory agencies also withdrew pholcodine-containing products based on similar findings from the ALPHO study.
Despite the relatively low absolute risk of pholcodine-associated POA with NMBAs, the seriousness of POA and the availability of alternative treatments for non-productive cough led HSA to conclude that the benefit of pholcodine did not outweigh the risk. As a result, all pholcodine-containing products were withdrawn in Singapore.
Given the extended risk period of pholcodine-associated cross-sensitization (12 months), anaesthesiologists and anaesthetists are advised to ask patients scheduled for general anesthesia involving NMBAs whether they have used pholcodine, particularly in the past year. This precaution is to maintain vigilance for potential NMBA-related POA in patients who may be at risk.
List of pholcodine-containing medicines registered as pharmacy-only medicines in Singapore
- Duro-Tuss® Forte Cough Liquid 45mg/15mL
- Duro-Tuss® Regular Cough Liquid 15mg/15mL
- Duro-Tuss® Expectorant Cough Liquid
- Duro-Tuss® Dry Cough Lozenges (Orange flavoured)
- Difflam® Blackcurrant Sugar Free Cough Lozenges
- Duro-Tuss® Decongestant Linctus [Not marketed locally]
- Duro-Tuss® Lemon Dry Cough Lozenges [Not marketed locally]
HSA: Health Sciences Authority; POA: perioperative anaphylaxis; NMBAs: Neuromuscular Blocking Agents; ALPHO: Allergy to Neuromuscular Blocking Agents and Pholcodine Exposure
Link to the HSA announcement: https://www.hsa.gov.sg/announcements/safety-alert/reminder-on-the-risk-of-pholcodine-associated-perioperative-anaphylaxis-with-neuromuscular-blocking-agents
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