Podcast
Questions and Answers
According to the prescribing cascade model, what can an adverse drug effect be misinterpreted as?
According to the prescribing cascade model, what can an adverse drug effect be misinterpreted as?
Which of the following is NOT considered a known risk factor for adverse drug events in older adults?
Which of the following is NOT considered a known risk factor for adverse drug events in older adults?
In the principles of prescribing for older patients, what is recommended when initiating drug therapy?
In the principles of prescribing for older patients, what is recommended when initiating drug therapy?
According to the principles of prescribing for older patients, what is the advice regarding starting multiple medications at the same time?
According to the principles of prescribing for older patients, what is the advice regarding starting multiple medications at the same time?
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What does the term ‘deprescribing’ refer to in the context of medication management for older adults?
What does the term ‘deprescribing’ refer to in the context of medication management for older adults?
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When a patient's CrCl or eGFR is approximately 10, how should drug dosing typically be adjusted?
When a patient's CrCl or eGFR is approximately 10, how should drug dosing typically be adjusted?
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Which of the following is most likely to be reduced in the aging liver, impacting drug metabolism?
Which of the following is most likely to be reduced in the aging liver, impacting drug metabolism?
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What is the effect of a decreased first-pass effect on the concentration of a parent drug?
What is the effect of a decreased first-pass effect on the concentration of a parent drug?
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What is the primary route of elimination for most medications via the kidneys?
What is the primary route of elimination for most medications via the kidneys?
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What is the usual recommendation regarding initial drug dosage in elderly patients given the changes in liver metabolism?
What is the usual recommendation regarding initial drug dosage in elderly patients given the changes in liver metabolism?
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Why is it crucial to calculate CrCl and eGFR when dosing drugs in older adults?
Why is it crucial to calculate CrCl and eGFR when dosing drugs in older adults?
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Which of the following is true regarding the use of CrCl and eGFR for drug dosing?
Which of the following is true regarding the use of CrCl and eGFR for drug dosing?
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In older adults, if serum creatinine (SCr) appears within normal range, what could be masked?
In older adults, if serum creatinine (SCr) appears within normal range, what could be masked?
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What is the average eGFR in a healthy young adult?
What is the average eGFR in a healthy young adult?
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If a medication is primarily eliminated renally, what would be a potential consequence of a decreased kidney function?
If a medication is primarily eliminated renally, what would be a potential consequence of a decreased kidney function?
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Which of the following best describes pharmacodynamics changes in older adults?
Which of the following best describes pharmacodynamics changes in older adults?
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What factor should be considered when calculating CrCl using the Cockcroft-Gault equation?
What factor should be considered when calculating CrCl using the Cockcroft-Gault equation?
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What is a common consequence of reduced drug elimination in older adults?
What is a common consequence of reduced drug elimination in older adults?
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Which of the following is true regarding how kidney disease affects drug elimination?
Which of the following is true regarding how kidney disease affects drug elimination?
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How is eGFR calculated?
How is eGFR calculated?
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What would be a consideration when making renal dosage adjustments?
What would be a consideration when making renal dosage adjustments?
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Study Notes
Drug Dosing in Special Populations
- Presentation focused on adjusting drug dosages for specific patient groups.
- Topics included renal and hepatic disease, as well as geriatric considerations.
Renal Disease
- Kidney disease affects drug elimination of most medications.
- Most water-soluble drugs are excreted by the kidney through glomerular filtration.
- Kidney function is measured by glomerular filtration rate (GFR).
- Average GFR in young, healthy adults is ~120-140 mL/min.
- By age 65, average GFR declines to ~50-60 mL/min.
- Equations like Cockcroft-Gault and CKD-EPI are used to calculate creatinine clearance (CrCl) and eGFR, respectively.
- CrCl = (140-age) × BW/(72×SCr) × 0.85(if female).
- eGFR values are recommended by the National Kidney Foundation to calculate kidney function.
- CrCl and eGFR should not be used interchangeably.
- Dosing adjustments are needed when CrCl or eGFR decreases to below 60 mL/min.
- Factors to consider when making renal dose adjustments include; consequences of overdosing, under-dosing, goal of therapy and dosing range of the drug.
- Tools for calculating renal function include Global RPh, calculators (multiple Creatinine Clearance Methods) and National Kidney Foundation calculator tools and MD Calc.
Hepatic Disease
- Most lipid-soluble drugs are metabolized by the liver.
- Hepatitis, an inflammation of the liver, reduces the liver's ability to metabolize drugs transiently.
- Cirrhosis permanently damages the liver, reducing its functional capacity and blood flow to the liver.
- Decreased blood flow to the liver reduces drug delivery to functioning hepatocytes.
- Child-Pugh score uses lab tests (albumin, bilirubin, prothrombin time) and clinical symptoms (ascites, hepatic encephalopathy) to evaluate liver function.
- Severity of cirrhosis is classified by the Child-Pugh score, with scoring systems used to categorize the level of liver damage.
- For drugs that are ≥60% metabolized by the liver, adjustments may include decreasing the dose by 25% for Child-Pugh scores between 8-9, or 50% if the score is above 10.
Geriatric Considerations
- Aging affects various aspects of drug metabolism and elimination.
- Older adults, sometimes exhibit a decrease in liver blood flow.
- A decrease in cardiac function also results in a decrease in liver blood flow, reducing drug delivery to the liver.
- Older adults typically have a reduced liver size.
- Older adults also may experience a reduction in the amount of enzymes necessary for drug metabolism in the liver.
- Age-related changes can also lead to lower GFR.
- Creatinine Production is also reduced with age.
- Factors to consider that can cause adverse drug events include; prior adverse drug reactions, low body weight or body mass index, age 85 and older and estimated CrCl less than 50ml/min.
- Lower CrCl and GFR values (less than 60 ml/min) for elderly adults may cause adverse effects.
- Principles for prescribing medications to older adults include; starting with low doses, slowly titrating to the necessary dose, avoid starting multiple drugs at once and consider deprescribing.
Practice Example
- A 67-year-old female taking gabapentin for neuropathy with other medical conditions is used as an example.
- Practical application of the principles discussed above.
Additional information
- Adverse drug events (ADEs) can arise from drug interactions, use of multiple drugs, or inappropriate dosages.
- A cascade, where one ADE prompts the use of further drugs, can lead to a chain of additional ADEs.
- General guidelines to avoid adverse effects for elderly patients include lower starting doses, slow increases in medications, avoiding starting several drugs at once, and considering deprescribing.
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Description
This quiz covers the critical aspects of adjusting drug dosages for special patient populations, focusing on renal and hepatic disease as well as geriatric considerations. It will assess your understanding of how kidney function impacts medication elimination and the importance of calculating creatinine clearance and eGFR for safe dosing.
