Drug-Nutrient Interactions in the Elderly

Objective: Manage successful aging by minimizing deleterious effects, preventing disabilities, and increasing HRQOL (Health-Related Quality of Life).
Frailty: Defined as a loss of physiologic reserve ( $multisystem impairment$ ) that increases susceptibility to disability from minor stressors.
Dimensions of Aging:
- Physical: Issues such as unintentional weight loss and balance problems.
- Psychological: Memory issues and coping difficulties.
- Social: Living alone or lack of support systems.
Statistic: At least $80\%$ of the elderly population has at least one chronic condition.

Institutionalized Drug Use: Average of $5$ agents per patient per month; $9\%$ take $10$ or more drugs daily.
Over-the-Counter (OTC) Use: Common for arthritis and constipation, including NSAIDs, insulin, and laxatives.
Dietary Supplements: Rising use of products such as Vitamin E, Gingko, Ginseng, Garlic, and St. John’s wort.
Vitamin E Risk: High doses may modulate insulin but increase bleeding risk with warfarin and potentially worsen infections.

Beers’ Criteria: A clinical list developed by Beers and colleagues to identify medications best avoided in the elderly.
Inappropriate Prescribing: Approximately $25\%$ of community-dwelling elderly receive potentially inappropriate medications.
Hospitalization Origins: Adverse drug events (ADEs) leading to hospitalization are most frequent for Cardiovascular ( $33.3\%$ ) and CNS ( $27.8\%$ ) therapies.

Physiologic Shifts: Decreased lean body mass, total body water, and albumin; increased body fat and gastric $pH$ .
Pharmacokinetic Changes:
- Absorption: Increased bioavailability for drugs with a high first-pass effect (e.g., fentanyl, propranolol, verapamil).
- Distribution: Lower albumin increases the free (active) fraction of acidic drugs. Increased body fat extends the half-life of lipid-soluble medications.
- Excretion: Declining renal mass and blood flow reduce creatinine clearance ( $CrCl$ ), usually requiring prospective dose adjustments.

Assessment Tools: Mini Nutritional Assessment (MNA) and S.C.A.L.E.S. ( $Sadness$ , $Cholesterol \lt 4.14\,\text{mmol/L}$ , $Albumin \lt 40\,\text{g/L}$ , $Loss\,of\,weight$ , $Eating\,problems$ , $Shopping\,problems$ ).
Identify Causes: The "MEALS ON WHEELS" acronym is used, starting with Medication as a primary treatable cause for weight loss.
Drug-Induced Mechanisms: Anorexia, malabsorption, or hypermetabolism caused by agents such as Digoxin, Metformin, and Laxatives.

Energy Requirements: Averaging $25\,\text{kcal/kg}$ daily.
Protein Requirements: Maintain at $1\,\text{g/kg}$ daily.
Fluid Requirements: Significant risk of dehydration; requires $30\,\text{mL/kg}$ daily.
Micronutrient Shifts: Higher requirements for Calcium, Vitamin D, $B_6$ , and $B_{12}$ ; lower requirements for Chromium and Vitamin A.

Physical Barriers: Food can alter gastric emptying rates or react physicochemically (e.g., chelation).
Fatty Meals: Decrease motility and gastric emptying, which affects drugs requiring rapid absorption or those unstable in acidic environments.
Herbal Interactions: St. John’s wort interacts with theophylline, cyclosporin, and digoxin. Ginkgo interacts with aspirin and warfarin.

Anticoagulants (Warfarin): Interacts with Vitamin E, Garlic, and Ginseng. Patients must maintain a consistent intake of Vitamin K foods.
Antiepileptics (Phenytoin): Interacts with tube feedings; folic acid can decrease phenytoin concentrations.
Antidepressants (MAOIs): Nonselective MAOIs interact with Tyramine (found in aged cheese, wine, and cured meats), potentially causing fatal hypertensive crises.
Antimicrobials (Tetracyclines/Fluoroquinolones): Chelate with polyvalent cations (Calcium, Magnesium, Iron, Aluminum) in dairy or antacids.
Endocrine (Metformin): May cause Vitamin $B_{12}$ malabsorption; calcium administration may mitigate this.
Osteoporosis (Bisphosphonates): Oral bioavailability is $\lt 1\%$ ; coffee or juice can reduce this by $60\%$ . Must be taken in a fasting state.
Gastrointestinal (PPIs): Acid-labile; should be administered with acidic juices (apple/orange) and avoided with milk.
Bile Acid Sequestrants/Laxatives: Cholestyramine and mineral oil can deplete fat-soluble vitamins ( $A$ , $D$ , $E$ , $K$ ).

Levodopa: Competes with large neutral amino acids from dietary protein for transport; interaction is significant in continuous enteral nutrition.
Weight Gain: Psychoactive drugs, Tricyclic Antidepressants (TCAs), and insulin often cause weight gain and carbohydrate cravings.
Diuretics: Lead to fluid/electrolyte imbalances, specifically hyponatremia and hypokalemia.
Corticosteroids: Cause sodium retention, potassium wasting, and calcium depletion, increasing osteoporosis risk.

Medication Appropriateness Index (MAI): Use Hanlon’s instrument for routine drug therapy evaluation.
Comprehensive Geriatric Assessment: A team approach covering functional, cognitive, social, and nutritional domains.
Education: Targeted programs and workbooks (e.g., Byeth and colleagues' warfarin workbook) effectively reduce adverse drug events and bleeding complications.