Enhancing Drug Therapy – Managing Pharmacokinetic and Pharmacodynamic Changes

Enhancing Drug Therapy – Managing Pharmacokinetic and Pharmacodynamic Changes

Pharmacokinetics deals with the study of drug activity when it enters the body. It involves four processes which include absorption from the route of administration to when the drug enters the body circulation, distribution to various tissues and fluids in the body, metabolism, which is the process of transformation of the medicine to simpler substances that can be absorbed in the body, and elimination where the drug is removed from the body. However, some medications may not be eliminated from the body completely. These processes determine the period the drug takes to give a response, the intensity, and the rate of onset. Pharmacodynamics involves the drug’s actions in the body, for example, side effects and mechanism of action. This process involves physiological and biochemical measures. The healing process can be slowed by various factors that affect the pharmacokinetics and pharmacodynamics of the patient (Anwar et al., 2021). These factors include the patient’s age, gender, comorbidities, and medications that the patient is using. In this case scenario, LM is an 86-year-old female with delirium. She is admitted to the emergency departed accompanied by her spouse, who confirms that she is compliant with medication according to the prescription given by her doctor. The spouse verifies that she does not check her blood pressure and heart rate at home. The patient does not have any known food and drug allergy and uses the following medications; APAP 650mg TID, multivitamin QD, warfarin 3mg OD, metoprolol XL 25mg QD, digoxin 0.25mg OD, and omeprazole 20mg QD. The medications that the patient is currently on, age, sex, and the patient’s past medical history affect the patient’s pharmacodynamics and pharmacokinetics.

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Selected Factors That Might Influence the Pharmacokinetic and Pharmacodynamic Processes in the Patient

LM is 86 years old, and as a person ages, the elimination of the drug by the kidneys decreases, especially from age 40, when the glomerular filtration rate decreases by 8mL/min/1.73m2. Despite the altered glomerular filtration rate, serum creatinine levels remained within the normal range because of reduced activity in older people and decreased muscle mass. In older patients, the function of baroreceptors is diminished, and the tone of peripheral veins is reduced, thus reducing the response of the drug in the cardiac, vascular, and pulmonary tissues. Her underlying conditions, such as osteoarthritis, GERD, hypertension, chronic kidney disease, and atrial fibrillation, can influence the distribution, absorption, and elimination of drugs in the body due to the loss or decreased functions of various systems. For example, the patient suffers from CKD, which can affect the excretion of drugs from the body due to impaired renal function. Using different medications to manage various conditions can reduce the bioavailability of some drugs and also reduce first-pass metabolism in the liver—some drugs, such as digoxin cause hyperkalemia associated with reduced excretion from the renal system. Changes in pharmacodynamics include increased sensitivity to various classes of drugs, such as cardiovascular drugs and anticoagulants. On the other hand, changes in pharmacokinetics involve an increased period of elimination of drugs due to an increase in the volume of distribution, especially in lipid-soluble medications, which causes decreased hepatic and renal clearance of drugs.

How Changes in the Processes Impact the Patient’s Recommended Drug Therapy

Changes in pharmacodynamics and pharmacokinetics negatively affect the recommended drug therapy because it alters preferred drug doses and interactions. Drug therapy is affected by changes in pharmacodynamics because some drugs cause adverse effects that can overwork some organs, such as the kidneys. Proton pump inhibitors such as omeprazole can result in acute kidney injury, leading to CKD if not treated early. Some medications used to manage heart conditions can also have side effects on the kidneys if not well controlled. Therefore, taking the drugs at low doses is advisable to prevent adverse effects on the body. Accumulation of waste products in the body due to reduced excretion of the drugs causes toxicity. It occurs due to changes in pharmacokinetics, such as reduced hepatic and renal clearance. This toxicity affects the liver and kidneys and can result in organ failure. If there are changes in the pharmacokinetics, the levels of the drugs taken should be investigated and corrected to prevent toxicity due to the accumulation of the drug in the body (Quiñones et al., 2021). The drug dose should be minimal to avoid drug-to-drug interactions and side effects. The underlying conditions in LM require various drugs to manage them; therefore, preventive measures such as reducing drug doses should be done to counter drug interactions. Anti-hypertensive medications such as digoxin, which causes elevated potassium levels, are already a threat to the kidneys that have already failed; therefore, their dose should be reduced to prevent interactions with other drugs like metoprolol and multivitamin. The mechanism of action of all these drugs is reduced, and their excretion is significantly reduced if they are administered simultaneously; therefore, taking the medications at different times to help them work effectively in the body is essential.

How I Will Improve the Patient’s Drug Therapy Plan

I will aim to improve the patient’s drug therapy plan depending on the changes in the pharmacokinetic and pharmacodynamic processes. The reason for improving drug therapy is to increase the drug’s effectiveness, prevent interactions with other medicines counter the effects those drug interactions will cause, and prevent the side effects of the drugs (Minichmayr et al., 2022) Since the patient’s kidneys have been damaged, I will put the patient on dialysis at least once a week to prevent the accumulation of waste products that will lead to toxicity. Some drugs, such as digoxin, have destructive side effects on the kidneys; therefore, I will replace it with diltiazem because its action mechanism is better than digoxin and has milder adverse effects. Diltiazem is a calcium channel blocker. Depolarization prevents the flow of calcium ions into the heart muscles, increasing muscle relaxation, decreasing blood pressure, and vasodilation of the arterial blood vessels. Its side effects include; sore throat, dry mouth, fever, fatigue, muscle pains, running nose, headache, dizziness, diarrhoea, constipation, vomiting, nasal congestion, and cough. The side effects of diltiazem are less severe than those of digoxin; therefore.

To sum it up, it is essential to check for the mechanism of action of each drug, its interactions with other drugs, and its side effects. When prescribing medications, it is important to consider the patient’s age, the underlying conditions, and the other medicines that the patient is using (Andrade et al.,2021). When taking the patient’s history, it’s essential to take notes from the person who accompanied them to the hospital to avoid missing important information that will help with investigations and diagnosis. In order to prevent comorbidities and side effects of the drugs, it is vital to alter the treatment plan when the pharmacodynamic and pharmacokinetic processes are affected by factors such as pre-existing medical conditions and the patient’s age.

References

Andrade, J. G., Wells, G. A., Deyell, M. W., Bennett, M., Essebag, V., Champagne, J., … & Verma, A. (2021). Cryoablation or drug therapy for initial treatment of atrial fibrillation. New England Journal of Medicine, 384(4), 305-315.

Anwar, M. K. M., Sarode, R. S., Sonune, A. G., Sayyad, S. T., & Kute, M. V. G. (2021) A Review On Controlled Release Drug Delivery System.

Minichmayr, I. K., Aranzana-Climent, V., & Friberg, L. E. (2022). Pharmacokinetic/pharmacodynamic models for time courses of antibiotic effects. International Journal of Antimicrobial Agents, 60(3), 106616.

Quiñones, L. A., Martínez, M. M., Cerpa, L. C., & Varela, N. M. (2021). Pharmacogenomics: Challenges and Future Perspectives. In The ADME Encyclopedia: A Comprehensive Guide on Biopharmacy and Pharmacokinetics (pp. 1-8). Cham: Springer International Publishing.

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Explain how the factor you selected might influence the pharmacokinetic and pharmacodynamic processes in the patient from the case study you were assigned.
Describe how changes in the processes might impact the patient’s recommended drug therapy. Be specific and provide examples.
Explain how you might improve the patient’s drug therapy plan and explain why you would make these recommended improvements.

Introduction, body and reference page

LM is an 86-year-old female admitted to the emergency department with delirium. Her spouse is with her and verifies that LM adheres to the medications she is currently prescribed. She does not self-monitor her BP or heart rate at home.

PMH:

A Fib was diagnosed 1 month ago

HTN x 10 years

CKD x 5 years

Osteoarthritis x 7 years

GERD x 20 years

Medications:

Digoxin 0.25 mg QD

Metoprolol XL 25mg QD

Warfarin 3 mg QD

APAP 650 mg TID

Omeprazole 20mg QD

Multivitamin QD

Allergies: NKDA

Social History:

Married to husband for 57 years
No smoking, alcohol, limited daily exercise (short walks each morning)
Family History:

None reported

Vitals:
Labs:

Wt 113 lbs Ht 5’4” Na+ 138 K+ 4.0
BP 101/58, HR 52 Cl- 99 CO2 27
BUN 33 Cr 1.2
Gluc 109 INR 3.8
Dig 2.4
PE:

Elderly female with altered level of consciousness, no signs of bruising, bleeding, or other injury.