Comprehensive Pharmacokinetics and Routes of Drug Administration

What is absorption in pharmacokinetics?

The process by which a drug enters the plasma from the site of administration.

What are the benefits of inhalation as a route of administration?

It allows rapid effects and targets lung conditions directly.

How does transdermal administration work?

It delivers systemic effects by applying drugs to the skin via a patch.

What is a common use for rectal administration of medications?

To deliver GI medications directly to the rectum without circulation.

Why are nasal routes used for medication administration?

For topical administration of medications specifically for nasal conditions.

What is the purpose of topical administration?

To provide local effects for conditions such as rashes.

What does parenteral administration include?

Intravenous, intramuscular, subcutaneous, intradermal routes.

Why should the subcutaneous route not be used with certain drugs?

It can cause necrosis and pain if the drug causes tissue irritation.

What is the primary advantage of parenteral drug administration?

Bypasses first-pass metabolism, allowing rapid onset and administration to unconscious patients.

What is the enteral route of drug administration?

Includes oral, sublingual, and buccal methods.

How do sublingual and buccal routes affect drug absorption?

They bypass first-pass metabolism and are rapidly absorbed.

What is enteric coating?

A coating that protects drugs from stomach acid.

What is the purpose of extended-release coating?

To slow the absorption of medication for prolonged effects.

What is passive diffusion in drug absorption?

Drug molecules pass through cell membranes easily if they are lipophilic.

What is facilitated diffusion?

A process that uses specialized transport proteins to cross cell membranes without ATP.

What is active transport in drug absorption?

Requires ATP and transport proteins to move drugs across cell membranes.

What is endocytosis in the context of drug absorption?

A process where very large drugs are engulfed by the cell and transported with vesicles.

How does pH affect drug absorption?

It influences whether drugs can lose or gain H+ to become uncharged, affecting membrane crossing.

What is bioavailability?

The rate and extent to which a drug reaches systemic circulation.

What is first-pass metabolism?

The process where the liver or GI tract metabolizes a drug before it reaches systemic circulation.

What is the role of P-glycoprotein in drug absorption?

It is a transporter protein that pumps drugs out of cells, decreasing absorption.

What factors can impact drug distribution?

Blood flow, capillary permeability, and binding to plasma or tissue proteins.

What is the blood-brain barrier?

A protective barrier that restricts drug diffusion into the brain, requiring lipid solubility or active transport.

What does a low volume of distribution (Vd) indicate?

More drug remains in the plasma rather than being distributed to tissues.

What is hepatic metabolism?

The process by which the liver metabolizes drugs to facilitate their excretion.

What is the difference between first-order and zero-order kinetics?

First-order eliminates a constant percentage of drug, while zero-order eliminates a constant amount.

What happens during phase 1 of drug metabolism?

Lipophilic drugs are converted into more polar molecules using cytochrome P450 enzymes.

What is phase 2 of drug metabolism?

Transforming drug metabolites into even more polar molecules for easier excretion.

What is the process of glomerular filtration?

Blood is filtered in the kidneys, allowing small molecules to pass while blocking larger ones.

What is proximal tubular secretion?

Active transport of substances from blood into the filtrate in the kidneys.

What is distal tubular reabsorption?

Passive diffusion of some molecules from the filtrate back into the blood.

What is ion trapping?

The process of changing urine pH to trap drug molecules in the filtrate for elimination.

What is steady-state concentration (Css)?

The point where the rate of drug elimination equals the rate of drug administration.

What is a loading dose?

A higher initial dose of a drug used to rapidly achieve therapeutic levels.

What is a maintenance dose?

The dose required to maintain drug levels within the therapeutic range.

What are the routes of drug administration?

Inhalation, transdermal, rectal, nasal, topical, parenteral, and enteral.

What is the advantage of inhalation as a route of administration?

It provides rapid effects for asthmatic and lung conditions.

What is transdermal drug administration?

Applying drugs to the skin via a patch for systemic effects.

Why are rectal medications used?

To reach the rectum directly without circulation, often for GI medications.

What is the purpose of nasal administration?

Topical administration for medications targeting nasal conditions.

What are the parenteral routes of administration?

Intravenous, intramuscular, subcutaneous, and intradermal.

Why should the subcutaneous route be avoided for certain drugs?

It can cause necrosis and pain if the drug irritates tissue.

What is enteral administration?

Administration via oral, sublingual, or buccal routes.

How does sublingual administration benefit drug absorption?

It bypasses first-pass metabolism and is rapidly absorbed.

What is the role of pKa in drug absorption?

It indicates how readily a drug will give up its H+; lower pKa means stronger acid.

What factors impact drug absorption?

pH, blood flow, surface area, contact time, and P-glycoprotein levels.

How is bioavailability calculated for oral medications?

By dividing the MG of a given medication by the amount left in the plasma.

What is the significance of solubility in drug absorption?

Drugs must be lipophilic yet have some solubility in aqueous solutions to be absorbed.

What is the difference between bioequivalence and therapeutic equivalence?

Bioequivalence means similar bioavailability; therapeutic equivalence means both bioequivalent and pharmaceutically equivalent.

What is the volume of distribution (Vd)?

A calculation to determine the amount of drug distributed to tissues versus the amount in plasma.

What is the role of the kidneys in drug elimination?

Most drug elimination occurs through the kidneys via glomerular filtration and tubular secretion.

What is ion trapping in drug elimination?

Changing urine pH to keep drugs charged and trapped in the filtrate for elimination.

What is the steady-state concentration (Css)?

The point where the rate of drug elimination equals the rate of drug administration.

How does half-life affect drug dosing?

Higher half-life means longer time to reach Css and longer elimination time.

What is the maintenance dose in pharmacokinetics?

The dose required to maintain Css within the therapeutic range.

What factors can increase a drug's half-life?

Decreased blood flow to liver/kidneys, renal or hepatic disease.

What is the significance of albumin in drug distribution?

Albumin binds to drugs in plasma, slowing their distribution to tissues.

What is the impact of capillary permeability on drug distribution?

Higher permeability allows easier distribution of drugs, except in the brain.

How does lipophilicity affect drug distribution?

More lipophilic drugs are generally easier to distribute throughout the body.

What is the role of tissue protein binding in drug action?

Tissues can store drugs, prolonging their effects and preventing them from returning to circulation.