Medicines for people on dialysis: dosing and safety

Dialysis does not behave like healthy kidneys. Some medicines are cleared well by the dialysis circuit, so a dose given before a session may be partly removed and may need replacing or timing differently. Others are too tightly protein-bound or too large to be filtered and stay in the body, building up if the dose is not reduced.

The Specialist Pharmacy Service tells prescribers to consider the dialysis type, how often it is done, the membrane used and the drug properties of protein binding and molecular size when choosing doses. There is no single table that fits everyone, and kidney pharmacists in dialysis units usually advise on difficult cases.

The NHS describes haemodialysis as taking place around three times a week, using a machine that filters the blood, and peritoneal dialysis as daily or overnight exchanges using the lining of the abdomen as the filter. Kidney Care UK explains that haemodialysis needs vascular access such as a fistula, a tunnelled line or, for short-term use, a temporary catheter.

Because the pattern of clearance differs, so does the advice on when to take certain tablets. Some patients on haemodialysis are told to take particular medicines after a session rather than before, while peritoneal dialysis, being continuous, can make timing less critical. Follow the unit's written advice for each medicine rather than assuming a rule that applied to another patient.

The NHS lists several types of medicine used in advanced kidney disease and dialysis. They serve different purposes, and most need regular blood tests to be adjusted.

• Phosphate binders, taken with meals, and vitamin D supplements to protect bones.

• Injectable or tablet medicines that stimulate red blood cell production, and iron supplements where deficiency is found.

• Diuretics such as furosemide to treat fluid build-up, where the kidneys still make urine.

• Blood pressure medicines including ACE inhibitors and angiotensin receptor blockers, and statins to lower cardiovascular risk.

• Treatments for high potassium, and advice to avoid potassium supplements.

Kidney Care UK advises that patients tell every healthcare professional about their kidney condition, because some over-the-counter medicines can worsen kidney function. It recommends avoiding effervescent tablets because of their sodium content and being cautious with paracetamol-containing products such as co-codamol. It also advises using one pharmacy where possible so the complete record can be checked.

The NHS says anti-inflammatory painkillers such as ibuprofen are to be avoided in CKD unless medically advised. People on dialysis who still pass some urine may be protecting what kidney function they have left, which is one more reason to avoid them.

People who have had a kidney transplant take immunosuppressant medicines that interact with many other drugs and some foods and herbal products. Specialist pharmacy guidance says medicines reviews for transplant patients should monitor for interactions with immunosuppressants and avoid nephrotoxic drugs such as NSAIDs. Any new prescription, including a short antibiotic course from a dentist or out-of-hours service, should be checked against the transplant list.

The NHS notes that about nine in ten transplants are still working after five years. Medicine adherence is a major part of keeping a transplant working.

Responsibility for prescribing is often shared. The dialysis unit may manage anaemia, bone and phosphate medicines and fluid, while a GP continues other long-term prescriptions. The Specialist Pharmacy Service advises that records should be updated across care settings so a hospital doctor, GP and community pharmacist see the same list.

Practically, carry an up-to-date list or app record, and say that you are on dialysis whenever you are offered a new medicine, including at pharmacies and hospital admissions. It is reasonable to ask whether a medicine has been checked for dialysis.