DRUG DOSING IN THE ELDERLY AND PEDIATRICS AND OBESE PATIENTS:

When it comes to administering medications, one size does not fit all. Special populations such as the elderly, pediatric patients, and individuals with obesity require customized dosing strategies to ensure safety, efficacy, and optimal therapeutic outcomes. Let’s dive into why and how these adjustments are made.

Drug Dosing in Pediatrics

Unique Challenges in Pediatric Dosing:
Children are not miniature adults; their bodies undergo significant growth and development that affects drug absorption, distribution, metabolism, and excretion. Neonates and infants, for instance, have immature liver and kidney functions, leading to slower drug clearance.

Dosing Methods in Pediatrics:

Weight-Based Dosing:
Medications are often prescribed based on weight (e.g., mg/kg).
Example: A child weighing 15 kg and needing a drug at 20 mg/kg/day would require 300 mg daily, divided into appropriate doses.
Body Surface Area (BSA) Dosing:
BSA-based calculations are sometimes used for more precise dosing.

Special Considerations:

Pediatric formulations often include liquid suspensions with calibrated droppers to ensure accurate dosing.
Flavor enhancements like cherry syrup improve compliance among children.

Drug Dosing in the Elderly

Physiological Changes with Aging:
As people age, organ functions decline, including renal and hepatic functions critical for drug metabolism and excretion. This makes older adults more susceptible to drug toxicity. Additionally, altered body composition, such as reduced lean body mass and increased fat, affects drug distribution.

Common Issues in Geriatric Dosing:

Increased sensitivity to certain drugs due to changes in receptor binding.
Slower clearance rates, necessitating lower doses or longer intervals between doses.

Tips for Safe Dosing:

Start Low, Go Slow: Begin with the lowest effective dose and adjust gradually.
Simplify regimens to promote adherence, especially for patients with cognitive impairments.
Monitor for drug interactions as elderly patients often take multiple medications.

Drug Dosing in Obese Patients

Impact of Obesity on Drug Pharmacokinetics:

Absorption: Generally unaffected, but the timing may vary due to altered gastric emptying.
Distribution: Lipophilic drugs (e.g., benzodiazepines) distribute more extensively into fat, while hydrophilic drugs (e.g., aminoglycosides) remain largely in lean tissue and plasma.
Metabolism: Fatty liver infiltration may impair liver function and alter drug metabolism.
Excretion: Obesity-related changes in renal clearance can influence drug elimination.

Dosing Adjustments in Obesity:

Use ideal body weight (IBW) or adjusted body weight (ABW) for dose calculations, especially for hydrophilic drugs.
IBW Formula:

ABW Formula:

Example:
For a 5’8″ male weighing 100 kg:

Conclusion

Drug dosing in the elderly, pediatric, and obese populations requires careful attention to their unique physiological characteristics. Whether it’s accounting for organ immaturity in children, slower metabolism in the elderly, or altered drug distribution in obesity, personalized dosing is key to ensuring therapeutic success and minimizing adverse effects.

For further reading, explore the full lecture notes by accessing the embedded PDF below!

PATH: PHARMD/ PHARMD NOTES/ PHARMD FIFTH YEAR NOTES/ CLINICAL PHARMACOKINETICS AND PHARMACOTHERAPEUTIC DRUG MONITORING (TDM)/ DRUG DOSING IN THE ELDERLY AND PEDIATRICS AND OBESE PATIENTS.