If you’ve ever heard doctors talk about "DPD deficiency" or seen a lab report mentioning DPD, you’re looking at the same enzyme: dihydropyrimidine dehydrogenase. This protein breaks down certain chemotherapy drugs, like 5‑fluorouracil (5‑FU), and some oral meds used for cancer. When DPD works well, the body clears these drugs safely. When it doesn’t, the drugs can build up, causing serious side effects.
Most people have enough DPD activity to handle standard doses. A small group, however, has low or missing activity because of genetic changes. Those changes mean the same dose of 5‑FU can be toxic, leading to nausea, mouth sores, or even life‑threatening reactions. The same story applies to capecitabine, a pill that turns into 5‑FU inside the body.
Beyond cancer drugs, DPD also processes some everyday medicines, like certain antivirals. If your doctor prescribes one of these, they might ask about any family history of drug reactions. Knowing your DPD status helps them choose the right dose or a different drug altogether.
Testing is simple and usually done before starting chemotherapy. A blood test measures DPD activity, and a genetic test looks for common mutations (like *DPYD* *2A*). If the results show low activity, doctors often reduce the dose or pick an alternative treatment. Some clinics even have protocols that adjust the dose based on the exact activity level.
If you already have a DPD deficiency, don’t panic. Most oncologists are familiar with the guidelines and will tailor your plan. Keep a list of all medications you take and share it with every new doctor. This helps avoid accidental prescribing of problematic drugs.
For patients who need 5‑FU‑based therapy, there are newer drugs that don’t rely on DPD for clearance. Discuss these options with your oncologist if testing shows a deficiency. The goal is the same: treat the cancer effectively while keeping side effects manageable.
In everyday life, you don’t need to do anything special if you’re not on a DPD‑related medication. Just stay informed and ask questions if a new prescription sounds unfamiliar. If you have a family member with a known DPD issue, let your doctor know – it can guide safer prescribing.
Bottom line: DPD is a key gatekeeper for certain drugs. Knowing whether you have enough of it can prevent nasty reactions and keep your treatment on track. Talk to your healthcare team about testing if you’re headed for chemotherapy or if you’ve had odd drug reactions before.
