Pharmacology 1

How the body handles drugs by drug absorbption, distribution, metabolism, and excretion.

AKA Metabolism

Non-ionized is absorbed better.

Active and inactive.

• 1) Attached to plasma protein for storage
• 2) Stored in fat
• 3) Stored in bone

Absorbtion, Deistribution, Metabolism, Excretion

Drug chemistry (i.e. solubility) route of administration, and coating of drug.

• Oral- Variable, slower absorbtion
• IM- rapid absorbtion (if aqueous), slower if lipid
• IV- fastest absorbtion
• Subcutaneous- same as IM
• Inhalation- rapid absorbtion
• Percutaneous or transdermal- incomplete or erratic absorbton
• Rectal- erratic absorbtion
• Sublingual- eliminates 1st pass effect
• Topical- incomplete erratic absorbtion

It must be soluble in water (and to a certain extent lipid).

Drugs that are protected from dissolving in stomach, coated with wax that only disloves in alkaline environment (in sm. intestine)

Part of drug disolves in stomach and part of drug disolves in sm. intestine.

Drugs absorbed in the stomach are made non-ionized by adding acid (ex. asprin). Drugs absorbed in the small intestine are made non-ionized by adding a base (ex. anphetamines)

If a drug (A) is alone 50% may bind to plasma protein and 50% will be active. If drug B is added to the mix, and B has a greater ability to bind to plasma protein, the B will bind to the plasma protein and less of A will bind to the plasma protien so more of A will be active.

Blood-brain barrier and placental barrier

Some drugs that are absorbed in the GI tract are metabolized in the liver before having an effect as an active drug, so a large first dose must be given or a build up of the drug over multiple doses must be done before a drug can be effective.

Hepatocytes contain microsomal enzymes that metabolize drugs in the liver.

Enzymes that convert an active drug to a toxic metabolite.

• 1) Ative --> Metabolized --> inactive
• 2) Active --> Metabolized --> Less active
• 3) Inactive --> Metabolized --> Active --> (6) less or inactive drug
• 4) Less active drug --> Metabolized --> more active drug --> (6) less or inactive drug
• 5) Ecretion with no metabolization

Age, nurttional status, genetic makeup, liver disease, hormones

Inhibiting the liver enzymes in some way sot that the break down of the drug occurs slower; it increases the level of the active drug in the body.

Simulating the liver enxymes and increases its ability to metabolize other drugs; it decreases the level of the drug in the body.

Glomerular flitration and tubular secretion.

Filtration moves drugs from blood to urine; protein-bound drugs are not filtered

Active; tubular "pumps" for organic acids and bases move drugs from blood to urine

Passive; lipid-soluble and nonionized drugs move back into the blood, polar and ionized drugs remain in the urine

Make the environment in the rine tract more acidic/basic to ionize the drug (ionized drugs will not be reabsorbed)

The plasma drug level

The plasma drug level below which therapeutic effects will not occur; the lowest level a drug is therapeuticly effective

The plasma drug level at which toxic effects begin

Between the Minimum effective concentration (MEC) and the toxic concentration

The time needed for the drug concentration to reach the minimum level

The time required for the maximum effect to occur after administration

The time during which blood levels are above the minimum effective concentration

The time needed for the plasma concentration of a drug to fall to 50% of its previous concentration; the faster the rate of metabolism, excretion, or both, the shorter the half-life

When the amout of drug eliminated between doses quals the dose administered, average drug levels will remain constant and plateau will have been reached.