Dialysis filters the blood when kidneys fail, representing a profound change for the patient. This therapy, necessary for individuals with End-Stage Renal Disease (ESRD), requires careful management of all prescribed medications. Since the body cannot naturally process drugs, prescriptions must be adjusted to prevent toxicity or maintain effectiveness. The dialysis procedure actively changes drug concentration, necessitating precise timing and dosing modifications.
How Dialysis Affects Drug Concentration
The process of dialysis significantly alters how the body handles medications, primarily through two mechanisms: clearance and volume shifts. Drug clearance during dialysis, known as dialyzability, depends on the drug’s physical properties, such as its molecular weight and protein binding capacity. Smaller, water-soluble drug molecules that are not tightly bound to plasma proteins are easily pulled across the dialyzer membrane and removed from the blood.
Conversely, drugs that are large, highly protein-bound, or widely distributed into body tissues are less susceptible to removal by the dialyzer. This can lead to subtherapeutic drug levels, meaning the medication may not be effective unless the dose is timed correctly to compensate for the loss.
Dialysis also involves the removal of large volumes of fluid from the patient’s circulation, creating immediate volume shifts within the body. This fluid removal can cause the concentration of certain drugs in the blood to increase or decrease rapidly. These shifts affect the drug’s volume of distribution, impacting its immediate concentration and effectiveness during the session.
Medications to Stop on Dialysis Day
Certain medications must be withheld immediately before a dialysis session due to the acute risk they pose during the procedure. The most common drugs held are those that can dangerously drop blood pressure when combined with fluid removal. This practice prevents immediate complications like severe hypotension.
Antihypertensives, used to control high blood pressure, are frequently held for four to six hours prior to the session. These include ACE inhibitors, ARBs, and some beta-blockers. Combining fluid removal with a potent antihypertensive can lead to intradialytic hypotension (IDH), which may cause fainting, shock, or harm to the dialysis access site.
Water-soluble vitamins, such as Vitamin C and the B-complex vitamins, are often withheld until after the treatment. Since these vitamins are readily cleared by the dialyzer, taking a supplement just before dialysis means the treatment will wash the beneficial nutrients away, wasting the dose.
Finally, certain highly dialyzable antibiotics should be held until the treatment is complete to ensure the medication remains in the body long enough to fight infection. If taken right before the session, the dialyzer quickly removes a significant portion of the drug. This rapid removal can drop the concentration below the therapeutic level, risking treatment failure and promoting drug resistance.
Medications Requiring Adjusted Timing
Some medications must have their timing shifted to prevent removal or manage the physiological effects of the treatment. These adjustments ensure the drug performs its intended function without being immediately cleared or causing an adverse reaction. The medication is still taken on dialysis day, just at a modified time.
Adjusting insulin and other diabetes medications is a primary example, as blood sugar levels can become unpredictable on dialysis days. The dialysis process can cause blood glucose to drop, increasing the risk of hypoglycemia. Insulin doses may be reduced by 10% to 15% on dialysis days, or the timing shifted to after the meal following the session.
Phosphate binders prevent the absorption of excess phosphorus from food. These drugs bind directly to phosphate in the gut, making administration timing dependent on food intake. They must be taken within a few minutes before or immediately after a meal or snack, including any food consumed during the dialysis session.
Anticoagulants and anti-platelet drugs, used to prevent blood clots, also require precise timing adjustments. Since a blood thinner like heparin is often administered directly into the dialysis circuit to prevent clotting during treatment, the timing of oral blood thinners must be managed carefully. The goal is to balance anticoagulation needs with the increased risk of bleeding when multiple agents are active simultaneously.
Patient Communication and Safety Protocols
Managing medications for a patient on dialysis requires clear communication between the patient and the medical team. Patients must keep an updated list of all medications, including supplements and vitamins. This list should be reviewed frequently with the nephrologist, dialysis nurse, or pharmacist.
Patients should never make changes to the dosing or timing of their prescribed medications. Any proposed change, even for a non-dialysis-related drug, must first be approved by the nephrology team. This ensures all care providers are aware of potential drug interactions or conflicts with the dialysis schedule.
If a dose is accidentally missed or taken incorrectly, the patient should immediately inform the dialysis staff or nurse. Medication reconciliation, comparing the patient’s medication list against new orders, should occur frequently, especially after any hospital stay or transition of care.