Discussion: Pharmacokinetics and Pharmacodynamics NURS 6521

Patient Scenario and Medical History

As an inpatient mental health I received a patient from Cook County Hospital Chicago, who had been the ward of the state for most of her life, she was a 28-year-old female with a history of schizoaffective disorder. This patient had been in and out of several psychiatric hospitals over the course of the last 5 years. There

Discussion Pharmacokinetics and Pharmacodynamics NURS 6521

were several other underlining past medical conditions that included, high blood pressure, type 2 diabetes mellites, elevated cholesterol, renal failure and GERD. Lack of stable placement in this young woman’s life resulted in her becoming non medication compliant. With her diagnosis of schizoaffective disorder, I knew that it was necessary for her to be involved in long-term treatment, to avoid relapses, and further hospitalizations. The short-term goal was to reduce symptoms of the diagnosis and delay future relapses and episodes, as there no general.

Pharmacodynamics and Pharmacokinetics

Van der Graaf & Benson 2011 suggests, “Drugs produce their effects by interacting with receptor targets, and drug discrimination is one behavioral procedure that is useful for investigating determinants of this interaction”. Evidence based research has proven that drugs can have different effects on the body, and this reaction of drugs in the body can be broken down into 2 parts that are referred to as pharmacokinetics and pharmacodynamics. Pharmacokinetics refers to how a drug navigates throughout the body system, while the concept of pharmacodynamics deals with is how the drug affects the body as well as its therapeutic or toxic effect in the body (Rosenthal, L. D., & Burchum, J. R, 2018).

Certain medical conditions generally affect the efficacy of psychotropic medications, they include acute and chronic kidney disease, heart diseases (Van der Graaf & Benson, 2011). Patients with these co-morbities have to be observed and monitored closely in pharmacotherapy to achieve optimum drug therapeutic effect. Some of the factors that influence pharmacokinetics of the patient include age and body composition. The malabsorption of the drug causes slower elimination which results in increased levels of the drug in the blood. There is an increased risk of adverse drug reactions because of the direct coloration of the dosage administered and how the body responds to the drug. The half-life of drugs that require metabolism and excretion can be remarkably longer in older people than in younger people (Le, 2020). It would also determine the route of administering medication. The general body composition of the patient such as body weight and height also influenced pharmacokinetics. However, pharmacokinetics also depends on the chemical properties of a drug. Pharmacodynamics may also have been influenced by similar factors.

Plan of care

To accurately establish the diagnosis of schizoaffective disorder, all other mental health issues including substance abuse and chemical dependency must be ruled out. I conducted a thorough head to toe physical assessment to establish a baseline and to find out any prior related complications. Following this I ran some routine tests and screenings, such as a urinalysis and drug screen test. The psychiatrist also requested that an MRI and CT scan be completed. A complete psychiatric evaluation was also done by a mental health professional, and then I collected more data afterwards on family and personal history, as well as issues regarding any major stresses or recent life changes. A full medication list, including dosages and frequencies of vitamins, herbal preparations and supplements, and the dosages

Medical treatment

A medication regimen that would fit the patient’s lifestyle is imperative due to a history of non-compliance with medication, the drug of choice ordered by the psychiatrist was targeted to relieve psychotic symptoms, maintain mood stability and depression. A monthly shot of Invega was prescribed for psychosis. Other drugs for mood stability and depression were prescribed on an as needed basis.

Psychotherapy

It was important to develop a trusting relationship with the patient as this allowed for strong therapeutic communication. The patient was able to understand some of the core dynamics of schizoaffective disorder, which leads to creating normalized thought patten and decrease symptoms. We also explored several other coping strategies for issues and concerns problems, relationships and coping strategies.

Reference

Le, J. (2020, October). Overview of Pharmacokinetics. Retrieved from https://www.merckmanuals.com/professional/clinicalpharmacology/pharmacokinetics/overview-of-pharmacokinetics

Rosenthal, L. D., & Burchum, J. R. (2018). Lehne’s pharmacotherapeutics for advanced practice providers. St. Louis, MO: Elsevier.

Van der Graaf PH, Benson N. Systems pharmacology: bridging systems biology and pharmacokinetics-pharmacodynamics (PKPD) in drug discovery and development. Pharm Res. 2011 Jul;28(7):1460-4. doi: 10.1007/s11095-011-0467-9. Epub 2011 May 11. PMID: 21560018.

     Pharmacokinetics and pharmacodynamics are two major relationships between medications and the body that should be considered when determining patient dosing (Rosenthal & Burchum, 2018). Pharmacokinetics is the absorption, distribution, metabolism, and excretion of a drug. Pharmacodynamics is the biochemical and physiologic effects of a drug.

Patient Case

Mr. K is a 10-years old male with a rare hereditary metabolic disorder glutaric aciduria type 1 (GA1) accompanied by neurologic impairment of speech, feeding difficulties, cerebral palsy, and spastic dystonia. The patient had periodic episodes of dystonic movements whenever he got happy or excited. He would have jerking movements of legs, tighten his body, fists his hands, and sometimes screams or cries. The patient enjoyed watching TV and watching other children play; unfortunately, those were some of his triggers at times. Sometimes the patient’s dystonic movements had no triggers. The patient’s dystonic movements could be periodic most of the day, lasting for up to a minute or the movements may start an hour or two before his next medication time. Mr. K could go a day without any dystonic movements, usually following exhaustion from two to three days of spasticity. The patient was on several medications, such as anticholinergics, benzodiazepine, and muscle relaxants. His primary medication was Baclofen (Lioresal), which he had four times a day through an enteral feeding tube to control his dystonia.

Pharmacokinetics and Pharmacodynamics

Dystonia refers to physical signs or symptoms of involuntary muscle contractions, and in children, it can cause motor disability (Adis Medical Writers, 2018). Dystonia can be acquired or inherited. In Mr. K’s case, his dystonia was due to genetic disorder GA1. Baclofen (Lioresal) is usually prescribed as a spasmolytic agent with GABA-B receptor agonist properties (Simon, Franchitto, & Rolland 2018). The medication comes in oral and intrathecal therapy. Oral Baclofen is rapidly absorbed in the intestinal tract, travels through the bloodstream, and binds with GABA-B receptors in the central nervous system (CNS) (Simon, Franchitto, & Rolland, 2018). Intrathecal Baclofen is administered directly to the spinal cord through a medication pump. Baclofen is metabolized in the liver and excreted by the kidney within 72 hours. The medication peaks plasma concentration in one hour and has a half-life of 3-6 hours.  Eighty-five percent of the drug is excreted unchanged by the kidney, and the remainder is excreted in the feces unchanged (Simon, Franchitto, & Rolland, 2018).

Baclofen binds on GABA-B receptors in the CNS, inhibits calcium influx, and reduces motor neuron excitability (Adis Medical Writers (AMW), 2018). Due to a short medication half-life, frequent administration is required for optimal effect. The maximum dosage is 60mg/day for children older than two years of age. Common adverse effects of Baclofen include drowsiness, dizziness, fatigue, constipation, and hypotonia at high doses. Baclofen cannot be discontinued abruptly due to the risk of withdrawal symptoms such as worsening spasticity, seizures, and hallucination.

Patient’s Personalized Plan of Care

Patient prevention, education, and health promotion should be included in the plan of care. Some conditions may become worse when Baclofen is abruptly stopped. Patient teaching should be centered on tapering medication dosage per healthcare provider’s orders. Urine output should be monitored while the patient is taking Baclofen to avoid toxicity. Sleep inducing and over-the-counter medications that cause drowsiness or mood changes should be avoided while on Baclofen. The provider should be notified of any increased dizziness or any change in the level of consciousness. Fall precautions should also be included in the patient’s plan of care while on Baclofen.

References

Adis Medical Writers. (2018). Tailor the pharmacological management of childhood dystonia to meet the needs of each child. Drugs & Therapy Perspectives, 34(5), 216–221. https://doi-org.ezp.waldenulibrary.org/10.1007/s40267-018-0495-1

Rosenthal, L. D., & Burchum, J. R. (2018). Lehne’s Pharmacotherapeutics for advanced practice providers. St. Louis, MO: Elsevier.

Simon, N., Franchitto, N., & Rolland, B. (2018). Pharmacokinetic Studies of Baclofen Are Not Sufficient to Establish an Optimized Dosage for Management of Alcohol Disorder. Frontiers in psychiatry, 9, 485.