NURS 6521 Discussion: Pharmacokinetics and Pharmacodynamics Discussion: Pharmacokinetics and Pharmacodynamics

 
In March 2020 Arkansas began to see the first surge of patients with coronavirus (COVID-19). In the beginning, treatment for the virus was based on oxygen saturation, and symptom management. By August 2021 monoclonal antibodies, Regen-Cov, casirivimab and imdevimab given together became the treatment of choice for the Delta strain of the virus under Emergency Use Authorization by the Food and Drug Administration (FDA.gov).

A 50 y/o male patient with moderate obesity and high blood pressure presented with cough, tachypnea and fever. He reported onset of symptoms eight days prior to seeking treatment and tested positive for COVID-19 using a rapid antigen test. His temperature was 102 degrees, heart rate 124, BP (Blood Pressure) 147/92 and oxygen saturation was 87%. The patient had no known drug allergies. He did not meet inclusion criteria due to his oxygen saturation but after doing some deep breathing, coughing, and sitting upright rather than lying down his oxygen saturation increased to 94% and remained there. The decision was made to give him Regen-COV. The patient was not vaccinated against COVID-19.

Individualized Plan of Care
Regen-COV 1200mg (casirivimab 600mg and imdevimab 600mg) was given subcutaneously using four injection sites and

administering 2.5 ml per site. The patient was asked to remain in a supine position for 10 minutes post injection to decrease the amount of irritation to the injection sites. He was monitored for one hour post injection with no change in vital signs or evidence of any adverse reaction to treatment. The patient was sent home with his wife, an oxygen saturation monitor and educational materials. He was instructed to do his deep breathing exercises every hour while awake.

The following afternoon I called the patient to reassess. He reported that his fever was resolving and had been no higher than 100 degrees since that morning. He reported feeling weak but not short of breath. His oxygen saturation was 94%. He felt like he was improving.

The patient was also called 48 hours after receiving monoclonal antibody treatment and reported, ¨I am sure you saved my life with that medicine. ¨ He was afebrile, and his oxygen saturation was 97%. He reported fatigue but his malaise was resolved. He reported no irritation at the injection sites and was instructed to follow up with his physician if his symptoms returned or worsened. I spoke to him one week post injection and he reported a full recovery and returned to work.

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Pharmacokinetics
Pharmacokinetics explain what the body does to the drug in terms of absorption, distribution, metabolism and excretion. (Rosenthal and Burchum, 2018). Regen-Cov is lab-created human antibodies given in combination (Food and Drug Administration, 2021).

Regen-COV has a half-life of 26-30 days and is degraded into small peptides and amino acids in the body. It is not metabolized by the liver or kidneys. Because of this, patient weight, hepatic or renal impairment do not affect exposure of the drug or require dose modification. It is also very unlikely that Regen-COV will interact with other medications (Deeks, 2021).

Pharmacodynamics
Pharmacodynamics is the study of the effects of the drug on the body and how the effects are produced (Rosenthal and Burchum, 2018. pp 22-23). Regen-COV antibodies have a high affinity for the spike protein of the COVID-19 virus. The antibody binds to the spike protein and prevents the virus from binding to human cells. This reduces the viral replication in the lungs and other body tissues (Deeks, 2021).

References 
Deeks, E.D. (2021, October 30). Casirivimab/Imdevimab: First Approval. Nature Public Health Emergency Collection, 81(17), 2047-2055. doi:10.1007/s40265-021-01620-z.

Food and Drug Administration. (2021). U.S. Food & Drug Administration. Retrieved from FDA.gov:

FDA.gov/drugs/drug-safety-and-availability/fda-authorizes-regen-cov-monoclonal-antibod