A case report highlighting drug-drug interactions between 3 life-saving treatments: Feminizing hormones, antiretrovirals and antituberculosis drugs.

We here present a case providing valuable insights for clinicians who deliver care to patients identifying as transgender or nonbinary. A 30-year-old trans woman presented to sexual health services requesting a routine sexual health screen and was subsequently diagnosed with HIV and syphilis. She started antiretrovirals for HIV (bictegravir/tenoforvir alafenamide/emtricitabine) 12 days later and was treated with benzathine penicillin G. The patient also had a positive tuberculosis (TB) ELIspot blood test result and further investigations proved the presence of active TB in the chest with mediastinal involvement. She commenced treatment for TB with quadruple therapy, including rifampicin. Due to the clinically significant interaction between rifampicin and bictegravir, the patient's antiretroviral treatment was switched to dolutegravir 50 mg twice daily in combination with tenofovir disoproxil fumarate and emtricitabine. As the patient had transitioned from male to female and was self-medicating with oestrogen-containing feminizing hormone therapy, her hormonal treatment was optimized and blood levels of oestradiol were closely monitored and titrated to manage the drug-drug interaction between rifampicin and oestrogen to ensure the latter would be maintained within the expected therapeutic range. Our case report demonstrates the importance of combining treatment of multiple conditions under 1 team ideally integrated with gender services to prevent multiple attendances and mismanagement of feminizing hormone therapies.