Pharmacokinetics Ppt Slides 1-31- Shannon

The liver is the primary organ responsible for metabolizing drugs in the body. It contains enzymes that break down drugs into smaller molecules, which can then be eliminated from the body. The liver plays a crucial role in drug metabolism as it helps to convert drugs into forms that can be easily excreted by the kidneys or eliminated through bile. This process ensures that drugs are effectively processed and eliminated from the body, preventing potential toxicity and allowing for proper drug efficacy.

The balance between absorption, distribution, metabolism, and elimination/excretion processes of pharmacokinetics determines the magnitude and duration of drug effects. Absorption refers to the process by which the drug enters the bloodstream from the site of administration. Distribution involves the movement of the drug throughout the body, reaching its target site. Metabolism refers to the chemical transformation of the drug into different compounds by enzymes in the body. Elimination/excretion is the process by which the drug and its metabolites are removed from the body, usually through urine or feces. The interplay between these processes determines the overall pharmacokinetics and, consequently, the effects of the drug.

Oral route of administration is considered the safest, most economical, and most common method. It involves taking medication through the mouth in the form of tablets, capsules, or liquids. This route is safe because it avoids the risks associated with invasive procedures like injections. It is also cost-effective as oral medications are generally less expensive compared to other routes. Additionally, oral administration is the most common method as it is convenient, easy to administer, and suitable for a wide range of medications.

When drugs are administered orally, they pass through the liver before reaching the rest of the body. The liver has enzymes that can metabolize the drug, reducing its concentration and effectiveness. This is known as the first pass effect. As a result, only a fraction of the drug (40-50%) reaches the central nervous system (CNS). This is why the bioavailability of orally administered morphine is lower compared to other routes of administration.

In this scenario, Little Billy has ingested a toxic chemical and is unconscious. In such a critical situation, ER physicians and PA's would most likely use the intravenous (IV) route of administration to administer the antidote for the toxin. IV administration allows for the rapid delivery of medication directly into the bloodstream, ensuring quick and efficient absorption of the antidote to counteract the effects of the toxin. It is the preferred route in emergency situations where immediate action is required.

The factors associated with the route of administration that affect drug absorption include blood flow to the absorption site, total surface area available for absorption, and contact time at the absorption surface. Blood flow to the absorption site determines the rate at which the drug is delivered to the site, while the total surface area available for absorption affects the amount of drug that can be absorbed. Contact time at the absorption surface determines how long the drug is in contact with the site, which can affect the extent of absorption. Therefore, all of these factors play a role in drug absorption.

The kidneys are the primary route of excretion for drugs from the body. They filter the blood and remove waste products, including drugs, through the process of urine formation. The kidneys play a crucial role in maintaining the body's homeostasis by eliminating drugs and their metabolites, ensuring that they do not accumulate and cause harm. The liver also plays a significant role in drug metabolism and elimination but is not the primary route of excretion. The lungs primarily excrete volatile substances, while the intestines mainly eliminate waste products from digestion.

AUC = area under the curve... see pg 9 for graph

The sublingual route of administration involves placing medication under the tongue, where it is absorbed into the bloodstream. This method is considered non-parenteral because it does not involve piercing the skin or bypassing the gastrointestinal tract. In contrast, the IV, IM, and subcutaneous routes are all parenteral, as they involve injecting medication directly into the body.

Facilitated diffusion also moves against the concentration gradient- but does NOT require energy... both facilitated diffusion and active transport can have competitive inhibition or carrier proteins can become saturated.

Passive diffusion refers to the movement of molecules across a membrane without the involvement of any facilitating factors. In this process, molecules move from an area of higher concentration to an area of lower concentration, driven by the concentration gradient. Unlike facilitated diffusion, which requires the assistance of transport proteins, passive diffusion occurs spontaneously and does not require any energy expenditure. Active transport, on the other hand, involves the movement of molecules against the concentration gradient, requiring the use of energy. Endocytosis is a process in which cells engulf substances by forming vesicles, which is not related to the net movement of molecules in the direction of lower concentration.

Pharmacokinetics refers to the study of how the body processes a drug, including how it is absorbed, distributed, metabolized, and excreted. It also includes the measurement and analysis of drug concentration at the site of action. However, pharmacokinetics does not directly encompass the clinical response to a drug, such as its toxicity and efficacy. These factors are influenced by pharmacodynamics, which focuses on how drugs interact with the body and produce their effects. Therefore, the correct answer is the clinical response to a drug, as it falls outside the scope of pharmacokinetics.

Based on the picture in the powerpoint it's inhalation, with IV as a close second, different sources say different things- so correct me if I'm wrong on this guys!

Inhalation is the exception because most drugs enter the venous side of circulation through IV injection, IM injection, or suppository. When drugs are inhaled, they are absorbed directly into the bloodstream through the lungs, bypassing the venous circulation. This route of administration is commonly used for respiratory medications and allows for rapid absorption and onset of action.

A drug that might cause an upset stomach if taken orally can alternatively be administered via the rectal suppository route. This route bypasses the gastrointestinal tract and allows the drug to be absorbed directly into the bloodstream through the rectal mucosa. By avoiding the stomach, the drug is less likely to cause an upset stomach and can still be effectively delivered to the body.

Transdermal and sublingual routes of administration completely bypass the first pass effect. The first pass effect refers to the metabolism of a drug that occurs in the liver before it reaches systemic circulation. However, drugs administered through the transdermal route are absorbed directly into the bloodstream through the skin, bypassing the liver. Similarly, drugs administered sublingually are absorbed directly into the bloodstream through the mucous membranes under the tongue, again bypassing the liver. Therefore, both transdermal and sublingual routes avoid the first pass metabolism, resulting in higher bioavailability of the drug.