The practitioner’s knowledge of pharmacokinetic and pharmacodynamic processes plays an important role in medication treatment prescribing and contributes to overall patient health outcomes. The patient’s individual characteristics can significantly influence the medication’s absorption and distribution capacities. Furthermore, inefficient drug excretion can present a threat to the patient’s health depending on the medication’s toxicity and side effects. The purpose of this paper is to explain how pharmacokinetic processes can change depending on the patients’ personal characteristics using the case example.
Firstly, the pharmacokinetic processes in the patient from the case study are influenced by his age, gender, and race. The primary factor that should be considered is the patient’s age. Older age in patients is generally associated with lowered levels of drug absorption because of reduced blood flow in the intestines and a slower metabolism. Furthermore, the changes in blood flow in the liver in older adults can result in a reduction in metabolism (Vaja & Rana, 2020). The liver is responsible for processing drugs into excretable water-soluble compounds. Low metabolism can significantly increase the bioavailability of drugs. While increased bioavailability of drugs presents an opportunity for the medication to reach its intended destination, increased bioavailability can result in drug overdose and an increased chance of a patient’s exposure to side effects.
The patient’s age implies that he takes several types of medications to treat different conditions simultaneously. Thus, there is a high chance for undesirable drug-drug interactions in the patient’s recommended drug therapy. The pharmacodynamics of drug-drug interactions can have an additive, synergistic or antagonistic effect. In some cases, competitive antagonistic effects can be used to counteract the effects of a drug; for example, naloxone can be used to counteract the effects of opioids (Roberts & Gibbs, 2018). The negative consequences of drug-drug interactions include reduced effectiveness of one of the drugs or side effects. Furthermore, while there is no specific evidence for the role of the increased bioavailability in drug-drug interactions, the risk of negative drug-drug interaction is higher with age-related modifications of pharmacokinetics and pharmacodynamics (Bories et al., 2021). Thus, the pharmacokinetic changes in the patient’s ability to process drugs in older age can negatively influence the pharmacodynamic processes of drug-drug interaction in recommended drug therapy.
The patient expressed that he experiences a slow heartbeat and dizziness after starting treatment with Diltiazem CD. Abnormally slow heart rates present one of the side effects of diltiazem because the drug prolongs refractory periods in AV nodes. When used with beta-blockers, the drug-drug interaction with diltiazem has an additive effect that contributes to cardiac conduction. Metoprolol is a beta-blocker drug used for the treatment of angina and chest pain. The patient’s dosage of Metoprolol was lowered when he started treatment with diltiazem, but negative side effects such as dizziness after getting up suggest insufficient extraction of Metoprolol.
Considering the patient’s age, I would recommend reducing the dosage of Metoprolol in accordance with age-related liver conditions. Reducing the dosage will eliminate the additive effect in drug-drug interaction between Diltiazem CD and Metoprolol, preventing side effects in slow heart rate and dizziness. Furthermore, reducing the dosage will allow an easier drug extraction process without reducing the drug’s bioavailability. Thus, exploring the case illustrated the importance of considering the patient’s individual characteristics for drug administration. The case also draws attention to the important problem of complex pharmacodynamics of interactions between multiple drugs in the elderly population receiving simultaneous medication treatment for several diseases.
References
Bories, M., Bouzille, G., Cuggia, M., & Le Corre, P. (2021). Drug–drug interactions in elderly patients with potentially inappropriate medications in primary care, nursing home and hospital settings: A systematic review and a preliminary study. Pharmaceutics, 13(2), 1-24. Web.
Roberts, A. G., & Gibbs, M. E. (2018). Mechanisms and the clinical relevance of complex drug-drug interactions. Clinical Pharmacology: Advances and Applications, 10, 123–134. Web.
Vaja, R., & Rana, M. (2020). Drugs and the liver. Anaesthesia and Intensive Care Medicine, 21(10), 517–523. Web.