Pharmacology Acid-Base Drug Absorption

Questions and Answers

Which pharmacokinetic factor is most crucial for a drug to cross cell membranes directly?

Hydrophilicity

pH of the surrounding fluid

Lipid solubility (correct)

Molecular weight

How do basic drugs behave in an acidic environment based on ion trapping?

They accumulate on the acidic side (correct)

They ionize and accumulate on the basic side

They remain uncharged

They are rapidly excreted

What is the primary role of P-glycoprotein in pharmacokinetics?

Facilitating drug absorption into the bloodstream

Transporting drugs into liver cells for metabolism

Transporting drugs out of cells to decrease drug accumulation (correct)

Breaking down drugs into inactive metabolites

What occurs when the pH of the fluid on one side of a membrane is different from the other side?

Drug molecules ionize based on the pH and accumulate on one side Signup and view all the answers

Which statement about acid drugs in basic environments is accurate?

They ionize and can accumulate in the urine Signup and view all the answers

In which body organ does P-glycoprotein transport drugs into the bile for elimination?

Liver Signup and view all the answers

Why do drugs need to be able to dissolve into the lipid membrane to enter the cell?

To diffuse directly through the lipids without assistance Signup and view all the answers

What is the consequence of aspirin being an acid drug in the stomach’s acidic environment?

It accumulates in the acidic gastric fluid Signup and view all the answers

Where do the majority of drugs get absorbed in the human body?

Small intestine Signup and view all the answers

What is the primary factor that determines whether a drug is ionized or non-ionized in different pH environments?

The pH of the environment Signup and view all the answers

Why do acidic drugs tend to be absorbed more readily in the stomach compared to basic drugs?

Acidic drugs become non-ionized in acid and absorb easily Signup and view all the answers

What characteristic of drugs allows them to cross the blood-brain barrier?

Lipid solubility of the drug Signup and view all the answers

What is the significance of pH partitioning in drug absorption?

It affects the rate and extent of drug absorption Signup and view all the answers

What happens to a basic drug absorbed in the stomach when it reaches the intestine?

It becomes uncharged and is absorbed through passive diffusion Signup and view all the answers

How does the rate of absorption affect the intensity of drug effects?

It influences how soon effects will begin Signup and view all the answers

When an acidic drug is taken orally, what is the expected outcome due to its interaction with stomach pH?

It remains non-ionized and is absorbed through passive diffusion Signup and view all the answers

How do acidic drugs behave in an alkaline environment regarding their solubility and absorption?

They become non-ionized and are lipid soluble. Signup and view all the answers

Which of the following statements correctly describes the absorption of basic drugs in an acidic environment?

Basic drugs become ionized and water soluble. Signup and view all the answers

Which factor has the greatest impact on the rate of absorption of a drug in the gastrointestinal tract?

The blood flow to the absorption site. Signup and view all the answers

What principle guides the movement of drugs across lipid membranes based on their ionization at different pH levels?

The pH dictates the ionization, thereby influencing lipid solubility. Signup and view all the answers

What is a critical characteristic of drugs that are primarily absorbed in the small intestine versus the stomach?

The large surface area of the intestine increases absorption efficiency. Signup and view all the answers

Which drug absorption route is considered the fastest, allowing for immediate circulation into the bloodstream?

Intravenous injection. Signup and view all the answers

How does the P-glycoprotein function in drug absorption?

It transports drugs out of cells, reducing their efficacy. Signup and view all the answers

What happens to a drug that is ionized in a lipid membrane environment?

It remains water soluble and unable to penetrate. Signup and view all the answers

Which of the following statements is true regarding the rate of dissolution as it relates to drug absorption?

Rate of dissolution varies based on the individual drug characteristics. Signup and view all the answers

Study Notes

Drug Absorption and Ionization

Acidic drugs in acidic environments remain non-ionized, making them lipid-soluble and able to diffuse into the bloodstream.
Aspirin, an acidic drug, ionizes and accumulates in the blood, facilitating delivery to target cells through ion trapping (pH partitioning).
Intestinal pH ranges from 6 to 7 (basic), while plasma pH is 7.4, indicating a basic environment in general circulation.

Absorption Mechanisms for Acidic and Basic Pills

Acidic Pill: Dissolves in acidic stomach, remains non-ionized, exits via passive diffusion into the bloodstream.
Basic Pill: Dissolves in acidic environment but becomes ionized (water-soluble) and remains in the stomach, traveling to the basic intestine to be absorbed.

Blood-Brain Barrier (BBB) Considerations

Drugs must be lipid-soluble to cross the tightly sealed capillary walls in the Central Nervous System (CNS).
Lipid solubility is crucial for drug access to brain tissue.

Rate and Amount of Absorption

Drug absorption is influenced by its movement from the site of administration to the bloodstream; this influences onset time and intensity of effects.

Transport Systems in Drug Absorption

P-glycoprotein plays a significant role in transporting drugs:
- Moves drugs from liver cells to bile for elimination.
- Transports drugs from blood to urine in kidneys.
- Facilitates drug movement between intestinal lumen and blood.
- Limits drug access to the brain by transporting drugs back into the blood.

Membrane Crossing Mechanisms

Direct diffusion requires drugs to be lipid-soluble due to the lipid nature of cell membranes.
Channels and pores are minimally used for drug transport; they are selectively permeable and mainly allow small ions like potassium and sodium through.

Factors Affecting Absorption

Rate of dissolution: Varies based on the drug formulation.
Surface area: Intestinal surface area is greater due to villi, enhancing absorption compared to the stomach.
Blood flow: Drugs are absorbed rapidly in areas with high blood flow.

Comparison of Absorption Rates by Route

Oral (GI) absorption is the slowest.
Intramuscular (IM) absorption is medium in speed.
Intravenous (IV) absorption is the fastest.

Gastrointestinal (GI) Absorption Process

Oral drugs absorbed from the GI tract pass through the portal vein, navigating the liver before reaching systemic circulation.

Pharmaceutical Preparations for Oral Administration

Tablets are forms of compressed powders.
Enteric-coated tablets dissolve in the intestine rather than the stomach.
Sustained-release capsules contain drugs that dissolve at varying rates throughout the day.

Additional Routes of Administration

Other methods include topical, transdermal, inhaled, rectal, vaginal, intravenous (IV), intramuscular (IM), and subcutaneous (Sub Q) routes.

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Description

This quiz explores the concepts of ionization and lipid solubility in the absorption of acidic drugs in different pH environments. It covers how these drugs accumulate in the bloodstream and their ability to diffuse across cell membranes. Perfect for students studying pharmacology or related health sciences.