Therapeutic drug monitoring

 

 

Therapeutic drug monitoring is a frequent practice in health care. How does age affect drug absorption, metabolization and excretion?
The use of salt substitutes can cause hyperkalemia in older adults when use in conjunction with what types of drugs?
Describe how you would prevent and evaluate risk factors for medication nonadherence in older adults?

Sample Solution

Let’s discuss the impact of age on drug pharmacokinetics, the risks of salt substitutes in older adults, and strategies to prevent and evaluate medication nonadherence.

1. Age-Related Changes in Drug Pharmacokinetics

Aging brings about physiological changes that can significantly alter how the body handles medications. These alterations can affect drug absorption, metabolism, and excretion, increasing the risk of adverse drug reactions and making it crucial to adjust dosages and monitor more closely.

  • Absorption:

    • Slower Gastric Emptying: Food and medications remain in the stomach longer, delaying absorption. This can be particularly important for drugs that are primarily absorbed in the small intestine.
    • Decreased Gastric Acid: Reduced stomach acid (common in older adults) can affect the dissolution and absorption of some drugs, especially those requiring an acidic environment.
    • Reduced Blood Flow to the Gut: Decreased mesenteric blood flow can diminish the amount of drug absorbed into the bloodstream.
  • Metabolism:

    • Reduced Liver Function: Liver size and blood flow to the liver decrease with age, and liver enzyme activity can also decline. This can impair the liver’s ability to metabolize drugs, leading to higher drug levels and prolonged effects.
    • Changes in First-Pass Metabolism: First-pass metabolism, which occurs in the liver before a drug enters systemic circulation, can be reduced, leading to a greater proportion of the drug reaching the bloodstream.
  • Excretion:

    • Reduced Kidney Function: Kidney function, as measured by glomerular filtration rate (GFR), declines with age. This is a major factor in reduced drug clearance, potentially leading to drug accumulation and toxicity.
    • Decreased Renal Blood Flow: Reduced blood flow to the kidneys further impairs the kidneys’ ability to filter and excrete drugs.

2. Salt Substitutes and Hyperkalemia

Salt substitutes often contain potassium chloride instead of sodium chloride. While helpful for individuals trying to reduce sodium intake, they can pose a risk of hyperkalemia (high potassium levels) in older adults, especially when used concurrently with certain medications or in the presence of impaired kidney function. The drugs that can increase the risk of hyperkalemia when used with salt substitutes include:

  • Potassium-sparing diuretics: These diuretics (e.g., spironolactone, triamterene, amiloride) reduce potassium excretion by the kidneys.
  • ACE inhibitors and ARBs: These drugs (used for hypertension and heart failure) can decrease potassium excretion and increase potassium levels.
  • Certain antibiotics: Some antibiotics, such as trimethoprim/sulfamethoxazole, can interfere with potassium excretion.
  • NSAIDs: Chronic use of NSAIDs can impair kidney function and increase the risk of hyperkalemia.
  • Digoxin: In patients taking digoxin, hyperkalemia can increase the risk of digoxin toxicity.

It’s crucial to educate older adults about the potential risks of hyperkalemia with salt substitutes, especially if they have kidney disease or are taking any of the above medications.

3. Preventing and Evaluating Medication Nonadherence in Older Adults

Medication nonadherence is a prevalent issue among older adults. Several factors contribute, including:

  • Complex regimens: Multiple medications, varying dosages, and complex schedules can be confusing.
  • Cognitive impairment: Memory loss, dementia, or other cognitive issues can make it difficult to remember medication schedules.
  • Physical limitations: Difficulty opening bottles, swallowing pills, or vision problems can hinder adherence.
  • Cost: Medication costs can be a significant barrier, particularly for those on fixed incomes.
  • Lack of understanding: Not understanding the purpose of the medication, how to take it, or potential side effects can lead to nonadherence.
  • Depression and social isolation: These factors can reduce motivation and support for medication adherence.

To prevent and evaluate medication nonadherence:

  • Simplify regimens: Collaborate with prescribers to minimize the number of medications and simplify dosing schedules. Explore combination pills or once-daily options where appropriate.
  • Provide clear instructions: Offer written and verbal instructions in plain language, ensuring the patient and caregiver understand the purpose of each medication, how to take it, and potential side effects.
  • Use memory aids: Recommend pill organizers, alarms, or medication reminder apps.
  • Address physical limitations: Consider alternative formulations (liquids, patches, crushed tablets) if swallowing is difficult. Provide assistance with opening bottles if needed.
  • Evaluate cost barriers: Discuss medication costs and explore options for assistance programs or less expensive alternatives (generics).
  • Assess understanding: Confirm the patient’s understanding of their medications. Use “teach-back” methods to verify comprehension.
  • Monitor for side effects: Regularly check for side effects and address any concerns promptly. Unpleasant side effects are a common cause of nonadherence.
  • Build a support system: Encourage involvement of family members, caregivers, or community resources to provide support and encouragement.
  • Regularly review medications: Periodically review all medications with the patient and their providers to ensure they are still appropriate and effective. This is also an opportunity to identify and address any adherence issues.
  • Motivational Interviewing: Employ motivational interviewing techniques to explore the patient’s beliefs and attitudes about their medications and identify any barriers to adherence.

By addressing these factors proactively, healthcare providers can improve medication adherence in older adults, leading to better health outcomes and reduced healthcare costs

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