Allopurinol hypersensitivity syndrome (AHS) affects approximately 1 in 1,000 patients prescribed allopurinol, with reported mortality rates between 20% and 25%. The risk of AHS is nearly 100 times higher in carriers of the HLA-B*58:01 allele than in noncarriers. Populations with a high allele frequency include Han Chinese (6%-8%), Korean (12%), and Thai (6%-8%) people. In this episode, Drs. Wid Yaseen and Jonathan Zipursky discuss their paper published in CMAJ, titled "Five things to know about…allopurinol hypersensitivity syndrome". Dr. Jonathan Zipursky is a general internist, clinical pharmacologist, and clinician scientist at Sunnybrook Health Sciences Centre. Dr. Yaseen is a second-year internal medicine resident physician at the University of Toronto. They argue that the syndrome's frequency is often underestimated and emphasize the importance of genetic testing in susceptible populations. Next, Dr. David Juurlink broadens the discussion beyond allopurinol to describe other common medications whose effectiveness and safety are significantly influenced by genetic predispositions. Dr. Juurlnk is a staff internist and head of division of clinical pharmacology and toxicology at Sunnybrook Health Sciences Centre in Toronto. He is also a medical toxicologist at the Ontario Poison Centre.  He explores the need for expanded genetic testing to protect patients and ensure proper dosing. Join us as we explore medical solutions that address the urgent need to change healthcare. Reach out to us about this or any episode you hear. Or tell us about something you'd like to hear on the leading Canadian medical podcast. You can find Blair and Mojola on Twitter @BlairBigham and @Drmojolaomole Twitter (in English): @CMAJ Twitter (en français): @JAMC Facebook Instagram: @CMAJ.ca The CMAJ Podcast is produced by PodCraft Productions