Appetite Stimulation in Dialysis Patients
Mirtazapine is the most practical medication for increasing appetite in dialysis patients, given at 15-30 mg orally at bedtime, with dose reduction needed in renal impairment. 1
Primary Pharmacologic Option
Mirtazapine (FDA-Approved Antidepressant with Appetite Effects)
Mirtazapine increases appetite and causes weight gain as a documented adverse effect, occurring in 17% of patients (compared to 2% with placebo), making this side effect therapeutically useful in dialysis patients. 1
Start with 15 mg orally at bedtime; the sedating effects are beneficial as they occur at night, and appetite stimulation occurs during waking hours. 1
Dose adjustment is mandatory in renal impairment: clearance is reduced by 30% in patients with GFR 11-39 mL/min/1.73 m² and by 50% in patients with GFR <10 mL/min/1.73 m². 1
Monitor for somnolence (54% incidence), dizziness (7%), and weight gain (12%), which are the most common effects. 1
Elderly dialysis patients require particular caution due to decreased drug clearance, increased risk of confusion, over-sedation, and hyponatremia. 1
The drug is 75% renally excreted, necessitating conservative dosing in dialysis patients starting at the low end of the range. 1
Alternative Pharmacologic Option
Megestrol Acetate (Progestational Appetite Stimulant)
Megestrol acetate at doses ≥320 mg/day can improve appetite and increase dietary energy and protein intake in hemodialysis patients, though it causes unfavorable body composition changes. 2
The major limitation is that megestrol increases fat mass substantially (up to 163% increase) while decreasing fat-free mass (up to 10.6% decrease), making it a second-line option. 2
Consider megestrol only when mirtazapine is contraindicated or ineffective, and when the priority is increasing caloric intake regardless of body composition effects. 2
Monitor body composition if possible, as weight gain may be misleading—representing fat accumulation rather than muscle preservation. 2
Experimental Option (Not Yet Standard of Care)
Ghrelin Administration
Daily subcutaneous ghrelin treatment immediately and significantly increases appetite with sustained effects throughout a week of treatment in malnourished dialysis patients. 3
Ghrelin increases energy intake at meals without changing energy expenditure, achieving a sustained positive energy balance. 3
This remains investigational and is not available for routine clinical use, but represents a promising future therapeutic strategy. 3
Addressing Underlying Causes of Anorexia
Optimize Dialysis Adequacy
Inadequate dialysis (Kt/Vurea <2.0 per week) causes uremic symptoms including nausea, vomiting, and anorexia that directly suppress appetite. 4, 5
Ensure weekly Kt/Vurea ≥2.0 and creatinine clearance ≥60 L/week/1.73 m² for high/high-average transporters or ≥50 L/week/1.73 m² for low/low-average transporters in peritoneal dialysis patients. 4
Increasing dialysis dose may improve appetite by reducing uremic toxins, though evidence for improved nutritional markers from dose increases alone is limited. 4
Manage Inflammation
Chronic inflammation produces proinflammatory cytokines that are directly associated with diminished appetite (anorexia) in dialysis patients. 4
Evaluate for and treat sources of inflammation including infections, inadequate dialysis, and cardiovascular disease, as these contribute to the malnutrition-inflammation-atherosclerosis syndrome. 6
Address Peritoneal Dialysis-Specific Factors
Peritoneal dialysis solutions cause abdominal discomfort and glucose absorption that may further impair appetite beyond uremia alone. 6
Increased peritoneal solute transport rate is linked to protein-energy wasting and poor appetite in PD patients. 6
PD patients demonstrate flattened daily appetite profiles with reduced premeal hunger peaks and less postmeal fullness variation compared to healthy controls. 7
Nutritional Support Strategies
Oral Nutritional Supplements (ONS)
Provide ONS when oral intake fails to meet ≥70% of daily macronutrient requirements, as ONS can improve nutritional status without negatively affecting regular food consumption. 4
ONS combined with dietary counseling should be attempted before considering intradialytic parenteral nutrition (IDPN). 4
Intradialytic Parenteral Nutrition (IDPN)
IDPN is reserved for malnourished hemodialysis patients who fail to respond to or cannot tolerate ONS or enteral nutrition. 4
IDPN provides nutrients during the 3-4 hour hemodialysis session three times weekly, offering a convenient route when oral/enteral routes are inadequate. 4
Multiple randomized controlled trials demonstrate nutritional improvements with IDPN in patients with overt protein-energy wasting, though it is not superior to ONS when ONS is tolerated. 4
Monitoring and Goals
Nutritional Assessment Parameters
Monitor protein equivalent of nitrogen appearance (nPNA) targeting ≥0.9-1.1 g/kg/day, as values below this suggest inadequate protein intake. 4
Assess serum albumin (maintain above lower limit of laboratory normal range), subjective global assessment (SGA), and edema-free body weight trends. 4
Evaluate for causes of decreased dietary protein intake including gastroparesis, comorbidity, chronic inflammation, and suboptimal dialysis adequacy. 4
Common Pitfalls to Avoid
Do not rely solely on patient-reported appetite, as dialysis patients normalize their appetite perception at lower nutrient intake levels than healthy individuals, making subjective reports misleading. 7
Do not restrict protein intake to <0.8 g/kg/day in dialysis patients, as malnutrition is a greater risk than the theoretical benefits of protein restriction. 8
Do not use megestrol acetate as first-line therapy due to unfavorable body composition changes favoring fat over lean mass. 2
Do not overlook reversible causes of anorexia (inadequate dialysis, inflammation, gastroparesis, medication side effects) before initiating appetite stimulants. 5