prompter: How do medicine / drugs get delivered to the place where they're needed? Or do they just get dispersed throughout the body?

assistant: Medicines or drugs can be delivered to the specific site in the body where they are needed through a variety of methods. The method of delivery depends on the type of drug, the condition being treated, and the desired effect. Here are some common methods of drug delivery:

1. Oral: The most common method of drug delivery is oral, where the drug is taken by mouth in the form of a pill, capsule, or liquid. The drug is then absorbed into the bloodstream through the digestive system and carried to the site where it is needed.
2. Intravenous (IV): Drugs can also be delivered directly into the bloodstream through an IV, where they can quickly reach the site of action. This method is often used in emergency situations or when a rapid effect is needed.
3. Injection: Drugs can be delivered into the muscle, under the skin, or directly into a specific body part or tissue through injection. This method allows the drug to bypass the digestive system and be delivered directly to the site where it is needed.
4. Topical: Some drugs can be applied directly to the skin, eyes, ears, or nose in the form of a cream, ointment, or drops. This method is often used for local conditions, such as skin infections or eye infections.
5. Inhalation: Drugs can be delivered to the lungs through inhalation, either through a nebulizer or an inhaler. This method is often used for respiratory conditions, such as asthma or chronic obstructive pulmonary disease (COPD).

Once a drug is delivered to the body, it can either be dispersed throughout the body or targeted to a specific site. The degree of dispersion depends on the drug's properties and how it is delivered. Some drugs are designed to target specific cells or tissues, while others are designed to be more general in their action. Ultimately, the goal is to deliver the drug to the site where it is needed in a way that maximizes its effectiveness and minimizes side effects.

prompter: The first three answers seem like delivery mechanisms to get the medication to the blood stream. Can you tell me more about the pharmacokinetics of those types of medications?

assistant: When we take medicine or drugs, they enter our bloodstream through various routes such as oral ingestion, injection, inhalation, or absorption through the skin. The drugs then travel through our bloodstream and get dispersed throughout the body. However, depending on the type of drug and the condition it is treating, it may need to be delivered to a specific part of the body.

To deliver drugs to a specific site, researchers have developed many targeted drug delivery systems. These systems use different techniques, such as encapsulating the drug in a specific carrier or attaching the drug to a specific molecule, to deliver the drug to the site of action. Additionally, some medications are designed to have a specific release rate or duration of action, which can affect how quickly it works and how long it remains in the body.

prompter: Give me example of a targeted drug delivery system.

assistant: Pharmacology is the scientific field that studies how the body reacts to medicines and how medicines affect the body. Scientists funded by the National Institutes of Health are interested in many aspects of pharmacology, including one called pharmacokinetics, which deals with understanding the entire cycle of a medicine's life inside the body. Knowing more about each of the four main stages of pharmacokinetics, collectively referred to as ADME, aids the design of medicines that are more effective and that produce fewer side effects.

The first stage of ADME is A, for absorption. Medicines are absorbed when they travel from the site of administration into the body's circulation. A few of the most common ways to administer drugs are oral (such as swallowing an aspirin tablet), intramuscular (getting a flu shot in an arm muscle), subcutaneous (injecting insulin just under the skin), intravenous (receiving chemotherapy through a vein) or transdermal (wearing a skin patch). Medicines taken by mouth are shuttled via a special blood vessel leading from the digestive tract to the liver, where a large amount of the medicine is broken down. Other routes of drug administration bypass the liver, entering the bloodstream directly or via the skin or lungs.

Once a drug gets absorbed, the next stage of ADME is D, for distribution. Most often, the bloodstream is the vehicle for carrying medicines throughout the body. During this step, side effects can occur when a drug has an effect at a site other than its target. For a pain reliever, the target organ might be a sore muscle in the leg; irritation of the stomach could be a side effect. Drugs destined for the central nervous system face a nearly impenetrable barricade called the blood-brain barrier that protects the brain from potentially dangerous substances such as poisons or viruses. Fortunately, pharmacologists have devised various ways to sneak some drugs past the blood-brain barrier. Other factors that can influence distribution include protein and fat molecules in the blood that can put drug molecules out of commission by latching onto them.

After a medicine has been distributed throughout the body and has done its job, the drug is broken down, or metabolized, the M in ADME. Everything that enters the bloodstream — whether swallowed, injected, inhaled or absorbed through the skin — is carried to the body's chemical processing plant, the liver. There, substances are chemically pummeled, twisted, cut apart, stuck together and transformed by proteins called enzymes. Many of the products of enzymatic breakdown, or metabolites, are less chemically active than the original molecule. Genetic differences can alter how certain enzymes work, also affecting their ability to metabolize drugs. Herbal products and foods, which contain many active components, can interfere with the body's ability to metabolize other drugs.

The now-inactive drug undergoes the final stage of its time in the body, excretion, the E in ADME. This removal happens via the urine or feces. By measuring the amounts of a drug in urine (as well as in blood), clinical pharmacologists can calculate how a person is processing a drug, perhaps resulting in a change to the prescribed dose or even the medicine. For example, if the drug is being eliminated relatively quickly, a higher dose may be needed.

prompter: Can you give an example or two? Like the process of taking oral Prozac disperses throughout my body compared to getting a vaccine shot in my shoulder.

assistant: Oral medications are swallowed, chewed, or placed under your tongue to dissolve. Medications that you swallow travel from your stomach or intestine into your bloodstream and then are carried to all parts of your body. This process is known as **absorption**.

When you take a medication orally, it goes through your digestive system and is absorbed into your bloodstream through the walls of your stomach or small intestine. The medication then travels throughout your body, including to the site where it’s needed.

In contrast, vaccines are injected into muscle tissue or under the skin, which allows them to be absorbed directly into the bloodstream.

prompter: Why are some things done via a pill and some not?