A route that does not involve the GI tract, including intravenous, subcutaneous, intramuscular, transdermal, intrathecal, and sublingual.
Albumin has an affinity for drugs, binding to them and eventually releasing them without expelling the drug.
An acid drug is a compound that ionizes in water to produce a proton. Most acidic drugs used in pharmacology are weak acids, which dissociate in water into a negatively charged anion and a proton. The neutral or non-polar form (AH) is the species that can be absorbed.
In acidic environments, weakly basic drugs become polar.
Using the GI tract to get the medication into the bloodstream, including oral and rectal administration.
A biological fluid.
The small intestine is a highly vascularized area with a greater surface area than the stomach. Its environment is highly basic (pH~8), and dwell time is controlled by digestive processes. Where the drug is absorbed depends on whether it is a weak acid or a weak base.
Weakly basic drugs are absorbed in the intestine.
Weakly acidic drugs are absorbed in the stomach.
Applying the drug directly to the area of injury, such as skin, inhalers, eye & ear drops.
Bypassing absorption as a pharmacokinetic step because the drug is put straight into the bloodstream.
If a drug isn't sufficiently water-soluble (i.e., fat-soluble), it cannot be administered intravenously (IV).
Weakly basic drugs remain in their non-polar form in basic environments.
Weakly acidic drugs exist in a non-polar, non-ionized form in the stomach.
Absorption, Distribution, Metabolism, Elimination/Excretion.
Drugs must pass through lipid-rich plasma membranes to enter the circulation.
The stomach is a dispensable, well-vascularized area with highly acidic fluids (pH 1-2 when fasted) and powerful hydrolytic enzymes that can destroy some drugs. Gastric pH and dwell time are controlled by digestive processes.
A compound that accepts hydrogen cations (protons) in water.
In a basic environment such as the intestine (pH=8), weakly acidic drugs become polar and are poorly absorbed.
Stomach -> Portal vein -> Liver -> Systemic circulation -> Target tissue -> Target cells
Biological fluids in the stomach and intestine are largely composed of water, creating a polar environment that dissolves drugs sharing the same physicochemical characteristics.
The most common form of drug administration, typically resulting in a relatively slower onset of action.
In acidic environments, weakly acidic drugs remain in their non-polar form, which is the species that can be absorbed.
Weakly basic drugs exist in a polar, ionized form in the stomach.
The first step is for the drug to dissolve, which involves unbinding from its excipients in the stomach and/or intestinal fluids.
Carrier-mediated transport is a process that requires energy, allowing drugs to move against the concentration gradient. Large or highly water-soluble drugs are actively transported across biological membranes to reach their target site.
The drug must be small in molecular size and sufficiently lipid-soluble to pass through biological membranes via diffusion.
Most basic drugs used in pharmacology are weak bases. When dissolved in water, these drugs associate with a proton and become positively charged.
As the pH of a solution decreases (becomes more acidic), the concentration of AH increases, leading to increased absorption of weakly acidic drugs.
The study of what the human body does to medication once the medication is in the body.
The movement of a drug from its site of administration across body membranes, and into circulating fluids (e.g., plasma).
The most common mechanism of drug absorption is passive diffusion, where the drug moves from a high concentration to a low concentration.
Drugs in a liquid suspension are easier to absorb.
Weakly basic drugs are poorly absorbed in the stomach because they exist in a polar, ionized form in an acidic environment.
Excipients add bulk to the tablet or capsule and can enhance or slow the rate of dissolution and alter the activity of hepatic enzymes, impacting the first pass effect.
If a drug is sufficiently water-soluble, it can be administered intravenously (IV), leading to a fast onset of action as it 'skips' the absorption process.
Route of administration, drug properties & formulation, blood flow at administration site, digestive motility, digestive tract enzymes and pH, and intestinal P-Glycoprotein (P-Gp).
In an acidic environment such as the stomach (pH=2), the electrically neutral non-polar form of the drug is favored, leading to absorption of weakly acidic drugs.
Weakly basic drugs exist in a non-polar, non-ionized form in the intestines.
