Question to the Department of Health and Social Care:

To ask His Majesty's Government how many yellow card reports of Post 5-Alpha Reductase Inhibitor Syndrome the Medicines and Healthcare products Regulatory Agency has received each year since 2019; and what medications those reports were tied to.

The Medicines and Healthcare products Regulatory Agency (MHRA) is responsible for ensuring medicines, medical devices, and blood components for transfusion meet applicable standards of safety, quality, and efficacy. The MHRA rigorously assesses available data, including from the Yellow Card scheme, and seeks advice from the Commission on Human Medicines, the MHRA’s independent advisory committee, where appropriate, to inform regulatory decisions including amending the product information.

Since 1 January 2019 up to and including 1 July 2026, the MHRA has received nine Yellow Card reports which include post 5-alpha-reductase inhibitor syndrome as a suspected adverse reaction. One report was received in 2023, with six reports being received in 2025, and five in 2026 thus far. The following table shows a breakdown of the medicines included in the nine Yellow Card reports received between 1 January 2019 and 1 July 2026, noting that one report can contain more than one medicine, and as such the sum of reports in the table will not equal the total number of unique reports:

Source: MHRA Yellow Card database.

It is important to note that Yellow Card reports capture adverse reactions as reported by the patient or healthcare professional, and this could be a syndrome or diagnosis, or underlying signs and symptoms. For a full breakdown of adverse reactions reported for medicines in the table above please view our interactive drug analysis profiles on the Yellow Card website.

It is important to note that a reaction reported to the Yellow Card scheme does not necessarily mean it has been caused by the medicine, only that the reporter had a suspicion it may have. Underlying or concurrent illnesses may be responsible, or the events could be coincidental. The number of reports received cannot be used as a basis for determining the incidence of a reaction, as neither the total number of reactions occurring, nor the number of patients using the drug, is known.