Introduction
In the chosen case scenario, the patient is a 62-year-old male who complains of “tingling in his feet and rashes in his private area.” During examination and physical assessment, the history of type 2 diabetes (A1C is 7.2 and Metformin 500 mg), a cardiac stent placement (six months ago), and depression symptoms are revealed. The man does not remember the names of medications he has recently taken, but he wants to get medications to cope with his depressed mood, coughing, and shortness of breath. A healthcare provider should address the basics of pharmacokinetics and pharmacodynamics and follow the evidence-based practice (EBP) guidelines to ensure appropriate medication selection and dosing and predict side effects.
Pharmacokinetics, Pharmacodynamics, and Medication Selection
Understanding the concepts of pharmacokinetics and pharmacodynamics is critical in medication selection to avoid errors and promote effective treatment. Woo and Robinson (2019) define pharmacokinetics as a branch of pharmacology that deals with drug absorption, distribution through the body, metabolism, and excretion. The route of administration affects the speed and duration of absorption and patient compliance. The way how drugs move defines their action before metabolization. Being metabolized, drugs are altered by enzymes and introduced as new molecules (Woo & Robinson, 2019).
Pharmacodynamics, in turn, is the branch of pharmacology that explains the mechanism of drugs’ action and their impact on the body system. It defines receptor sensitivity and chemical interactions to clarify the relationship between the required dose and the expected response. Physiologic changes may be provoked by specific diseases, patient age, and the combination of several drugs and be the reason for pharmacodynamic inconsistencies.
In this case, metformin is a first-line pharmacological treatment for a diabetic patient. Its antihyperglycemic effect is due to the “inhibition of hepatic glucose output,” meaning the liver is its primary functional site (Song, 2016, p. 187). Metformin reduces glucose levels in the blood and increases glucose uptake and insulin signaling, but its mechanism of action remains poorly explored and is associated with controversies (Song, 2016). Its half-life is about 5-6 hours; it is not metabolized and is usually excreted unchanged in the urine (Woo & Robinson, 2019).
In most cases, metformin is effective in controlling glucose levels, which is evidenced by lower A1C levels. The patient under analysis has 7.2 in its A1C, which signalizes absorption or dosing problems. There are many effects of metformin on the human body, including vitamin B12 deficiency, which may explain fatigue, loss of interest, and tingling in the hands and legs (Woo & Robinson, 2019). Thus, it is important to examine the required dosing of metformin and evaluate its side effects not to promote new problems.
Dosing and Side Effects
A common dose of metformin for diabetic patients is 500 mg a day. In the case under analysis, the patient does not remember what he takes and how often he should take medications, which may cause his current health changes and deterioration. Pharmacokinetics reveals the relationship between drug dose and its concentration in the body. Metformin is 50% absorbed after oral administration and bound to plasma proteins (half-life is 6.2 hours) and the blood (half-life is 17.6 hours) (Woo & Robinson, 2019). It is also necessary to follow the fasting condition because food decreases its absorption by 40% (Woo & Robinson, 2019).
There are two critical contraindications to using metformin: metabolic acidosis and renal dysfunction (if serum creatinine exceeds 1.5, renal functioning is under threat) (Woo & Robinson, 2019). Although lactic acidosis is rare, the patient should be attentive to such signs as appetite loss, stomach discomfort, and diarrhea. Considering this information, the recommended dosing of metformin for the patient remains 500 mg daily.
EBP Guidelines and Pharmacokinetic Impact
Diabetes is a chronic disease that leads to multiple changes in the human body, including cardiovascular problems, kidney failure, and blindness. Peripheral neuropathy is observed in about 50% of adults with diabetes, depending on their age, weight, hypertension management, and smoking habits (Hicks & Selvin, 2019). There are many EPD guidelines to manage painful diabetic peripheral neuropathy. For example, the US Food and Drug Administration approves duloxetine and pregabalin but warns about the side effects of tricyclic antidepressants in diabetic patients (Hicks & Selvin, 2019).
The current patient can be prescribed gabapentin 300 mg daily for one week (Medscape, 2022). No severe interactions between gabapentin and metformin are observed, and effective seizure control is observed. The patient uses an albuterol inhaler but suffers from cough and shortness of breath. Compared to inhalers that require coordination, nebulizers deliver more accurate doses. It is also important to ensure that the required portion of albuterol is regularly taken every four hours. To manage his shortness of breath and productive cough, the patient has to stop smoking because this habit is dangerous for diabetic people.
Conclusion
In general, improving the awareness of pharmacokinetics and pharmacodynamics is a critical skill for all healthcare providers. There are many chronic conditions that cannot be treated, and their management affects other treatment courses. In the offered case, the patient is diabetic and poorly aware of his pharmacological treatment plan. He regularly smokes despite increased complaints of coughing and shortness of breath. He is recommended to continue taking metformin 500 mg, replace his albuterol inhaler with a nebulizer, and take gabapentin 300 mg to manage his tingling in the feet.
References
Hicks, C. W., & Selvin, E. (2019). Epidemiology of peripheral neuropathy and lower extremity disease in diabetes. Current Diabetes Reports, 19(10). Web.
Medscape. (2022). Gabapentin (Rx). Web.
Song, R. (2016). Mechanism of metformin: A tale of two sites. Diabetes Care, 39(2), 187–189. Web.
Woo, T. M., & Robinson, M. V. (2019). Pharmacotherapeutics for advanced practice nurse prescribers (5th ed.). F. A. Davis.