NUR 520 STU Examination of Pharmacokinetics Discussion


Modern psychopharmacology is largely the story of chemical neurotransmission. One must be fluent in the language and principles of chemical neurotransmission to:

  • Understand the actions of drugs on the brain.
  • Grasp the impact of diseases upon the central nervous system.
  • Interpret the behavioral consequences of psychiatric medicines.

After studying Module 2: Lecture Materials & Resources, discuss the following:

  • Choose an FDA-approved medication currently used in psychiatry.
  • Explain the concept of that drug’s half-life.  
  • How long would it take for that drug to reach a steady state?  
  • How frequently should the medication be dosed based on the half-life? 
  • Use as a reference for this assignment.

respond to at least two of your peers:

Michelle Smith

One FDA-approved medication used in psychiatry is fluoxetine, which is marketed under the brand name Prozac. Fluoxetine is an SSRI antidepressant, which stands for selective serotonin reuptake inhibitor. Fluoxetine generally works by balancing certain chemicals in the brain which may have become disturbed. It is often used to treat depression, sometimes obsessive-compulsive disorder, and bulimia. It works by increasing the levels of serotonin in the brain. Serotonin is thought to influence mood, emotion, and sleep positively. Serotonin and norepinephrine, both biological amines, have been shown to play a role in depression. Low concentrations of serotonin appear in the cerebrospinal fluid of patients with depression. Additionally, lower numbers of serotonin uptake sites are located on the platelets of patients with depression.

Fluoxetine should be administered once a day, either in the morning or evening and started at 20 mg daily. It is essential to note that the drug can be administered in smaller doses. For an individual with poorly tolerated side effects, the drug may be dosed in 10 mg tablets instead of 20 mg tablets to help minimize any side effects. It also comes in a delayed-release capsule formulation with dosing at 90 mg per week. “Evidence suggests that the efficacy of the delayed-release formulation (90 mg once weekly) is similar to that of individuals receiving fluoxetine 20 mg daily.” (Sohel et al.,2022)

The half-life of a drug refers to the period taken for a drug to reduce by half in concentration ( Andrade, 2022 ). The period is determined once a single drug is administered to the body. This concept is applied in establishing the dose – relationship of a medication. Some multiple factors and elements establish the half-life of different medicines. They include whether the medication has been metabolized or broken down. Other factors include dosage and the chemical structure of the drug. In other words, if a drug has a half-life of 24 hours, then after 24 hours, there will be only half as much of the drug in the body as there was initially. For Fluoxetine, its half-life is relatively long, at around four to six days. It takes several days for the body to eliminate just half of the initial dose. As a result, fluoxetine can accumulate in the body over time with repeated dosing and may take several weeks to reach steady-state levels. The long half-life of fluoxetine can have both advantages and disadvantages.

On the one hand, it means that patients may only need to take one dose per day or even less frequently than that. On the other hand, if someone experiences side effects from taking fluoxetine or needs to stop taking it for any reason, they may need to wait several days or weeks before all traces of it are eliminated from their system. Understanding a medication’s half-life is essential for determining dosing schedules and potential associated risks. 

Shahbaz, Zarvish

Chemical Neurotransmission

Drug treatment for mental illness is the focus of contemporary psychopharmacology. One of the cornerstones of the field of psychopharmacology is the notion of chemical neurotransmission, which describes the exchange of information between neurons in the brain through chemical messengers known as neurotransmitters. Understanding chemical neurotransmission terms and ideas is necessary for appreciating how drugs affect the brain and how they could be utilized to treat mental health disorders. The brain’s synapses are an intricate network that enables neurons to communicate. When a nerve impulse reaches a neuron’s terminal, the neuron releases neurotransmitters into the synapse. When these neurotransmitters bind to their receptors on the receiving neuron, they cause the cell to release and send a whole new electrical signal.

FDA-Approved Medication

One FDA-approved medication now in use in the field of psychiatry is Prozac (Fluoxetine), also known by its generic name. Prozac, a selective serotonin reuptake inhibitor (SSRI), is often used to treat mood disorders such as sadness, anxiety, and OCD. The increased serotonin levels in the brain aid in mood regulation and alleviate the symptoms of depression and anxiety. Prozac comes in various tablet, capsule, and liquid oral solution forms. One dose per day is recommended, taken at any time of day. It may take several weeks for Prozac to start working, so even if your symptoms improve, you should continue taking the prescription as directed (Epocrates, 2023c). Even while Prozac is effective in treating mental health disorders, it has drawbacks. Rarely, Prozac may increase the likelihood of suicidal thoughts or behaviors, especially in children and young adults. It’s important to talk to your doctor about the risks and benefits of Prozac before starting treatment.

The Concept of the Drug’s Half-Life

A drug’s half-life is when it takes half of the drug to be eliminated from the body. It is a fundamental concept in pharmacology since it helps doctors determine a drug’s optimal dosing schedule and maintenance period. For instance, the half-life of Prozac (Fluoxetine) is around seven days (Epocrates, 2023b). This means that after four to six days, just 10 milligrams of a 20-milligram dosage of Prozac will remain in the body. After the following seven days, only half of the remaining dosage (5 mg) will be left.

How long for the drug to reach a steady state

In medicine, a steady state is usually reached after seven half-lives. Therefore, 20–30 days would be needed for Prozac to achieve a steady state in the body. Blood levels of the medication will have leveled out to a point where its full therapeutic influence may be assessed. The half-life of Prozac dictates that it be taken once a day. It allows the medicine’s concentration in the blood to stay constant while the body gradually eliminates it. The frequency of doses, however, may be affected by the individual’s needs and the severity of their condition.


You must understand chemical neurotransmission to understand how mental health drugs affect the brain and how they may be administered. Mental health drugs work best when brain neurotransmitters are active. Central nervous system diseases may impair a person’s mood, behavior, and health. Psychiatric drugs may cause tiredness, changed appetite, weight gain, and addiction or reliance. Prozac, an FDA-approved medicine for depression, anxiety, and OCD, is widely used in psychiatry. Understanding a drug’s half-life is important when determining dose and effect duration. With this information, healthcare providers may make informed pharmacological treatment choices for their patients and better comprehend drugs. 

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