The physiological changes associated with aging can significantly affect the pharmacokinetics of drugs.
- The increase in gastric pH, the decrease in gastric emptying rate, and the decrease in GIT blood flow associated with aging can affect the absorption of drugs.
- The change in body composition in older individuals (decrease muscles and increase fat) can affect the distribution of drugs.
- The decrease in kidney function and the decrease in enzymatic capacity in older individuals can affect the elimination of drugs.
- Also, older patients use more drugs which increases the probability of drug interactions.
- Penicillin G which in mainly excreted unchanged in urine is eliminated at a much slower rate in older patients (> 65 years).
- This slower rate of penicillin G elimination results from the decreased renal function in older patients.
- Propranolol which is eliminated completely by metabolism has significantly longer in older patients.
- This is because of the decreased metabolic capacity in older patients.
