Mr. P. is a 78 year old man with chronic obstructive pulmonary disease (COPD) who is making his first visit to your office. In addition to several COPD exacerbations, he has a history of atrial fibrillation after a surgery 2 years ago, mild renal insufficiency, hypertension, benign prostatic hyperplasia, "sinus troubles" and depression. His recent complaints include insomnia and dizziness especially when standing up, for which he saw two other physicians who prescribed diazepam and meclizine; as well as worsening confusion and anorexia. His son brings Mr. P. into your office, along with a bag of medications: albuterol inhaler 2puffs 4 times daily, hydrochlorothiazide 50mg per day, potassium chloride 24mEq per day, digoxin 0.25mg per day, methyldopa 250mg 4 times daily, amitriptyline 75mg daily at bedtime, terbutaline 5mg po 3 times daily, meclizine 25mg 3 times daily, diazepam 5mg daily at bedtime, diphenhydramine 50mg daily at bedtime as needed (he takes this for "sinus congestion" and sleep), and Dimetapp 1cap daily at bedtime as needed for "sinus troubles".

Q: What are some of the potential problems with this medical regimen?

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Aging and Pharmacology

• Drug absorption-little effect of aging
• Drug distribution-clinically meaningful changes occur
  • Decreased serum albumin may increase amount of free drug
    • most important for highly protein-bound drugs (aspirin, warfarin, furosemide, benzodiazepines)
  • Altered volume of distribution (Vd)
    • Decreased total body water and lean body mass with aging - affects water soluble drugs
      • may have decreased Vd, increased drug levels
      • these changes affect most antibiotics, digoxin, lithium, alcohol
    • Increased body fat with aging - affects fat-soluble drugs
      • Increased Vd, increased half-life
      • these changes affect most psychotropic agents
• Metabolism: aging effects complex
• Excretion: most predictable aging effects
  • 50% average decrease in renal function between age 20-90
  • Serum creatinine levels may be normal in older people despite significant decline in renal function, due to age-related decline in muscle mass and creatinine production
  • Renally excreted drugs:
    • Increased half-life and duration of action
    • Drugs tend to accumulate
    • Bottom line for drugs w/narrow therapeutic/toxic ratios: measure creatinine clearance and/or drug levels
• Pharmacodynamics: changes less well-known
  • Elderly are more sensitive to some medications (e.g., benzodiazepines)
  • Older people are less sensitive to beta-adrenergic drugs (e.g., propranolol)

   

Medication Management

• Polypharmacy: a major problem in frail older patients.
  • Potential causes:
    • failure of patient/caregiver to discontinue medications as intended by the physician
    • prescribing by multiple physicians
    • failure of physician to review the medication profile periodically
    • using multiple pharmacies
    • poor compliance
• Gathering Data in Pre-Hospital Stage
  • Attempt to identify what patient is taking
  • Determine whether the patient has written medication instructions
  • Bring in medicines with patient
  • Enlist help of others to identify current medicines
  • Don't forget over-the-counter medicines
• When Administering Medications:
  • Know pharmacology of drugs
  • Obtain history of major preexisting conditions
    • Coronary artery disease, congestive heart failure, chronic obstructive pulmonary disease/asthma, diabetes mellitus, renal/liver failure
  • "Start low, go slow"
  • Older people may be more sensitive to drug effects, and may tend to accumulate some drugs to a higher level
    • Minimize risk by beginning medications at a reduced dose and titrating dose up gradually
    • Remember: symptoms of drug toxicity may occur at "therapeutic" levels (e.g., lithium, digoxin)
  • Note potential drug-drug, drug-disease interactions
  • For renally excreted drugs:
    • use nomogram or formula to estimate creatinine clearance to determine dose
  • Consider issuing a Mediset (a pill box to organize a week's worth of medications)

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University of Washington, Division of Gerontology and Geriatric Medicine

Copyright 1999, 2000 David A. Gruenewald, M.D. and Kayla I. Brodkin, M.D. All rights reserved.