The use of prescription drugs has substantially increased with age. Today, almost 90% of the older population regularly takes prescription drugs. Besides, this proportion rises with dietary supplements and over-the-counter drugs. Hence, drug use is the highest in elderly patients and nursing home residents.
Understanding these higher prevalence rates, optimizing drug therapy through pharmacokinetic studies is crucial. Pharmacokinetic assays help understand absorption, distribution, metabolism, excretion, and bioavailability profiles. However, there is a difference between bioavailability and bioequivalence profiles. Bioavailability refers to the extent of drug compounds being available at the site of drug action, whereas bioequivalence compares the bioavailability between two drug products.
So, let us understand the role of pharmacokinetic CROs in helping optimize drug therapy for the elderly population.
Pharmacokinetic studies for the elderly
Providing effective and safe drug therapy is challenging for older populations. Some primary reasons for these difficulties include:
- The elderly population use more drug products and hence has an increased risk of drug interactions and adverse effects
- Most elderly populations have chronic disorders, and hence, may have different drug responses and drug effects
- The pharmacokinetic and pharmacodynamic profile of a drug product may be altered through aging
- Besides, they may find it challenging to obtain or buy pharmaceutical drug products
Hence, physicians and healthcare providers focus on two primary approaches to optimize and deliver drug therapies to older adults:
- Use appropriate drug products as indicated so that they are highly cost-effective
- And avoiding adverse drug reactions by administering correct doses, avoiding drug-disease and drug-drug interactions, and stopping unnecessary use of drug products
Most importantly, overprescribing is a significant issue in older adults, increasing the risk of adverse drug reactions. However, underprescribing should also be avoided.
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With aging, absorption, distribution, metabolism, and excretion properties can change clinically. Metabolism and excretion properties decrease with age. Besides, the toxicity of drug products can increase as drug concentrations of chronic drug products increase for 5 to 6 half-lives.
Age-related issues such as high gastric PH, low gastric emptying, and small bowel surface area may affect the drug absorption properties. Besides, body fat generally increases with age, and the total body water may also decrease. These changes meaningfully impact the distribution characteristics of a drug product.
Notably, metabolism through cytochrome p40 enzymes also decreases with age. Hence, decreased hepatic metabolism can reduce drug clearance by 30 to 40%. The rate of drug metabolism, depending on age, may vary from person to person and may require individual dose adjustments.
Renal elimination is one of the most vital PK changes associated with aging. With an increase in age, the glomerular filtration rate decreases, affecting the overall elimination of a product from the body. As renal elimination contributes to the systemic elimination of a drug product, aging has clinical implications on the pharmacodynamic properties of a drug product.
In conclusion
The pharmacokinetic properties of a drug product change with aging. Hence, drug products intended for the elderly population should consider different modifications in the pharmacokinetic properties for eliciting adequate therapeutic responses with limited adverse reactions.