NURS 6521 Week 1: Basic Pharmacotherapeutic Concepts

  

​The patient scenario to be discussed for the purpose of this discussion post is a patient being treated with intravenousvancomycin for a Methicillin Resistant Staphylococcus Aureus (MRSA) infection in a spinal surgical incision. The patient had multiple comorbidities; however, the most pertinent comorbidity is end-stage chronic renal disease. Common practice in this setting is to order pharmacokinetic services to monitor and assist with management of vancomycin administration. The monitoring includes laboratory studies including blood chemistries and vancomycin levels. During the monitoring, it was discovered the patient had an extremely high level of vancomycin in the blood which required holding the next scheduled dose, and changing the amount of Vancomycin provided in the next dose.

 

Factors Influencing Pharmacokinetics and Pharmacodynamics

Vancomycin is a glycopeptide antibiotic that is hydrophilic and cannot pass through the cells membranes through simple diffusion resulting in a need to be administered intravenously to achieve a systemic result (Zaric, et al., 2018). Vancomycin reaches a peak level, which is 63 mcg/mL, in the blood and falls to about 23 mcg/mL in about two hours after the infusion, and then continues to decrease to 8mcg/mL about 11 hours after the end of the infusion in an individual without any renal impairment (Connective Rx, 2018). The concentration of vancomycin in the blood is also impacted by the degree of inflammation (Connective Rx, 2018). The pharmacokinetics factors, which is what the body does with the drug (Arcanfelo, Peterson, & Reinhold, 2017), influencing the patient’s response to the medication are influenced by the impaired kidney function. Approximately 80%-90% of vancomycin is excreted in the urine (Zaric, et al., 2018).

Review of the pharmacodynamics, the way the drug impacts the body (Arcanfelo, Peterson, & Reinhold, 2017), reveals vancomycin inhibiting bacterial synthesis through binding to the precursor on bacterial cell walls (Connective Rx, 2018). Through the binding of vancomycin to the precursor unit of the bacterial cell wall, the outcome is RNA synthesis inhibition, alteration of the bacterial cell wall permeability, and bacterial cell death (Connective Rx, 2018). Severe adverse reactions related to the renal function include renal failure, azotemia, and interstitial nephritis (Connective Rx, 2018). Moderate adverse reactions include hypokalemia and hypotension (Connective Rx, 2018). Vertigo and dizziness are mild symptoms that can be related to kidney function (Connective Rx, 2018). In renal patients the doses have to be adjusted due to the possibility of accumulation of the medication causing nephrotoxicity (Connective Rx, 2018). Nephrotoxicity occurring as a result of monotherapy is usually reversible (Connective Rx, 2018).

 

Personalized Plan of Care

​The plan of care for this patient was for him to have vancomycin on the days he would have dialysis to assist with the excretion of the medication. Labs were drawn frequently to monitor the kidney function and vancomycin trough levels and dose adjustments were made accordingly. Collaboration with the pharmacokinetics pharmacist and the provider was also crucial to the management of the outcome of the patient.

 

Conclusion

In conclusion, the above-mentioned patient was given vancomycin for a MRSA infection and he had a co-morbidity of ESRD. The ESRD impacted the excretion of the vancomycin resulting in toxic levels of vancomycin in the patient’s blood. The pharmacokinetics and pharmacodynamics significantly impact the action of the medication and magnitude of the impact on the body. The individualized plan of care for the specified patient created the possibility to limit any further renal impairment.

References

Arcanfelo, V. P., Peterson, A. M., & Reinhold, J. A. (2017). Pharmacotherapeutics for Advanced Practice: A Practical Approach. Ambler, PA: Lippincott Williams & Wilkins.