You have a 58 year old African American male that is coming in for a follow-up visit after recently having a Myocardial infarction which was successfully treated via angioplasty.  He was started on Metoprolol for his consistently elevated high blood pressure during his hospital stay.

His primary diagnoses include:

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SAMPLE SOLUTION

 

Student Name

South University

NSG6005 – Advanced Pharmacology

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Week 1 Case Study

Adrenoceptors and Metoprolol selectivity (Pharmacodynamics)

Metoprolol is a drug from the category of selective β1-adrenoceptor antagonist because it acts selectively on β1-adrenoceptors, which are located mainly in the cardiac muscles. This selectivity enables metoprolol to slow down the heart rate and decrease the strength of heart contractions, all without impacting the β2-adrenoceptors in the lungs and blood vessels. This selectivity is crucial when dealing with CAD and MI because it reduces the heart’s workload and its requirement for oxygen. As stated by the 2020 International Society of Hypertension Global Hypertension Practice Guidelines, selective beta 1 receptor antagonists are preferred in patients with heart disease since they help reduce heart rate to prevent further cardiac events (Unger et al., 2020). This makes metoprolol well-suited for this patient, especially since he recently had an MI.

Metoprolol Pharmacodynamics: Effects on the Cardiovascular System

Some important actions of metoprolol in the cardiovascular system are as follows. It is a β1-selective blocker with both a negative chronotropic effect and a negative inotropic effect on the heart. This decrease in contractility and heart rate consequently results in reduced cardiac output and myocardial oxygen demand, decreasing the likelihood of angina and other ischemic events in patients with CAD. Metoprolol also decreases blood pressure through the modulation of sympathetic nervous system impulses. These effects are helpful in the control of high blood pressure, especially in hypertensive patients with a history of MI, to reduce pressure on the heart and reduce its oxygen demand. This mechanism also shares similar insights with guidelines from the National Center for Biotechnology Information (NCBI) recommending β1-selective blockers in managing cardiovascular diseases, particularly among post-MI patients (NCBI, 2018).

Metabolism of Metoprolol (Pharmacokinetics)

Metoprolol is mainly metabolized in the liver, with most of the drug being converted to various active metabolites through the CYP2D6 enzyme system. This implies that the drug undergoes first-pass metabolism, in which a large percentage of the drug is eliminated, and only a small amount reaches the systemic circulation. Differences in the CYP2D6 enzyme may also come from genetic polymorphisms, which may lead to different metabolisms of metoprolol among individuals and varying drug concentrations. For instance, CYP2D6 poor metabolizers may accumulate the drug, raising the probability of side effects, while CYP2D6 rapid metabolizers may experience low drug effectiveness. It is important to note the pharmacokinetic profile of metoprolol because it impacts dosing and the need for drug monitoring, especially in patients with defined genetic polymorphism of the CYP2D6 gene. The American Heart Association guidelines describe the pharmacokinetic process to express that patient metabolism should be considered when selecting cardiovascular medications (American Heart Association, 2020).

Special Consideration When Initiating Treatment for Diabetes, CAD, Asthma, and Hypertension

Patients with such a medical history as type 2 diabetes, coronary artery disease, asthma, and hypertension require cautious adherence to clinical recommendations for medication use. According to the JNC 8 Guidelines, beta-blockers should not be used as first-line antihypertensive medications in diabetic patients unless there is a contraindication, like a previous history of myocardial infarction or heart failure. In this case, the patient has had a recent MI, and metoprolol is the right option, given its cardioprotective properties. On the other hand, it is crucial to manage blood pressure and pay attention to symptoms of hypoglycemia, as beta-blockers can make it hard to notice low blood sugar levels.

Concerning asthma, metoprolol has a relatively high β1-selectivity, thus avoiding the risk of bronchoconstriction commonly associated with non-selective beta-blockade. This is especially important for patients with asthma, as in this case, who may use albuterol as required for mild intermittent symptoms. It should, however, be noted that although metoprolol is safer for asthmatic patients, any form of beta-blocker can occasionally impact the respiratory system. As for diabetes treatment, metformin should still be an adequate treatment since the patient is well-maintained with an HgA1c of 6.7%. However, it is crucial to note that metoprolol can mask the signs of low blood sugar, especially in a patient taking medications for diabetes.

Therefore, according to the JNC 8 guidelines, the American Heart Association, and the IHS Division of Diabetes Algorithm for hypertension, metoprolol is suitable for this patient with previous myocardial infarction if proper control of blood pressure, respiratory condition, and blood glucose levels are maintained.

 

References

American Heart Association. (2020). 2020 American College of Cardiology/American Heart Association (ACC/AHA) Hypertension Guidelines. Retrieved from American Heart Association.

Indian Health Service (IHS) Division of Diabetes. (2020). Algorithm for the Management of Hypertension in Adults with Diabetes. Retrieved from IHS.

National Center for Biotechnology Information (NCBI). (2018). Effects of Beta-Blockers on Cardiovascular Diseases. Retrieved from NCBI.