Introduction
Many prescription and over-the-counter drugs are useful and sometimes effective in treating symptoms or eliminating the causal agents of different diseases. Accordingly, benzodiazepines and narcotics are designed to achieve different intrinsic effects including muscle relaxation, anxiolytic, sedative /hypnotic, amnesic, and anticonvulsant effects (Lacy et al., 2004, pp. 1-10). Therefore, these medications are useful in treating acute seizures caused by other drugs such as anti-malarial drugs, anxiety, and insomnia. However, their prescription is for short-term uses to avoid overdependence, which is a major side effect besides anterograde amnesia, tolerance, depression, benzodiazepine withdrawal syndrome, and paradoxical effects. Studies note that the side-effects are more prominent in children and the aged persons (Lacy et al., 2004). One of the most notable side-effects of benzodiazepines and narcotics among the elderly entails their ability to cause reduced renal function or failure. In this essay, the effects of benzodiazepines and narcotics on the kidney function decline among the elderly are elaborated.
The effects of benzodiazepines and narcotics on the kidney function
It is certain that with age, the ability of the kidneys to perform their functions effectively is highly reduced. Here, studies note that the kidneys are bound to become smaller besides their mass reducing by 30% due to glomerulosclerosis. The ultimate effect of these changes involves compromised kidney functions as a result of lower rates of renal blood flow (RBF) and the glomerular filtration rate (GFR), which decrease by 10% per decade and 1-1.5% per annum respectively. Furthermore, the rate of creatinine clearance by the kidneys reduces by 1% for persons above 40 years. Moreover, the rate of urine concentration among the elderly is highly reduced due to the lowered response to the Anti-diuretic Hormone (ADH) (Smith, 2008).
Despite that the foregoing changes in kidney function are attributed to various physiological changes in the kidney, studies implicate benzodiazepines and analgesic narcotics in the genesis of some impaired renal functions including reduced renal drug clearance, which is exacerbated by the presence of certain illnesses. According to (Smith, 2008, p. 384), the physiological changes observed among the elderly including decreased fat mass, reduced body water, and decreased muscle mass serve to alter the pharmacokinetic properties of benzodiazepines and analgesic narcotics in many ways. For instance, the duration of effect of some lipophylic drugs like lidocaine and fentany increases among the elderly due to the reduced fat mass, which means that less drug components will remain bound by the fat matter. On the other hand, the distribution rate of morphine (water-soluble) will be highly reduced due to low body water, and thus, morphine’s plasma concentration will increase with normal doses. The increased plasma concentration of morphine may lead to an increase in dose-related side-effects (Smith, 2008).
Furthermore, the drug half-life for benzodiazepines and analgesic narcotics increases with a decrease in renal drug clearance. Here, studies note that lipophylic drugs like lidocaine and other narcotic analgesics may reach their peak plasma concentration because they are highly dependant on the first-pass metabolic processes before reaching the liver. Consequently, their ability to cause dose-related side-effects such as nephrotoxicity is increased particularly in the presence of impaired cardiac output due to illnesses. Further, studies note that phase I reactions (Oxidation, Hydrolysis, and Reduction) are highly altered among the elderly persons. Here, these reactions are bound to diminish irrespective of the CYP P-450 enzyme catalyzing the reactions (Smith, 2008, p. 385). As a result, drugs such as diazepam and acetaminophen undergo metabolism by different enzymes at the same rate irrespective of the person’s age. Conversely, the metabolism of fentanyl and carbamazepine by the microsomal CYP P-450 enzymes is highly reduced with age. Overall, these drugs are bound to accumulate in the body thereby causing various pharmacokinetic effects such as reduced renal drug clearance and tissue toxicity including the kidneys, which will highly reduce their overall functionality.
Conclusion
The foregoing discussions illustrate the effects caused by benzodiazepines such as diazepam and narcotic analgesics such as morphine on the functionality of the kidneys among the elderly. From the discussions, it is worth-noting that the above-mentioned drugs do not have a direct impact on the kidney functions and that is why they are recommended in treating various complications in some patients already suffering from renal impairment. However, in the presence of various illnesses, physiological alterations, and aging effects, their pharmacokinetic properties may be altered, and as a result, their distribution, plasma concentrations, metabolism, and elimination may be compromised leading to kidney toxicity and diminished drug clearance.
References
Lacy, C.F., Armstrong, L.L., Goldman, M.P., & Lance, L.L. (2004). Drug information handbook (11th ed.). Hudson, Ohio: American Pharmaceutical Association and Lexi-Comp Inc.
Smith, H.S. (2008). Current therapy in pain. New York: Elsevier Health Sciences.