Chapter 2

Pharmacokinetics

How the drug moves and modifies in the body

Features absorption, distribution, metabolism, and excretion (drug elimination/clearance mechanisms)

Absorption

Route of administration to the bloodstream

Distribution

How drugs circulate from the bloodstream to target cells. Carried by the blood and tissue fluids

Affected by drug-protein binding and circulation

Metabolism

AKA biotransformation

Drugs being altered from their original form to a new form done by cytochrome p-450 (CYP) liver enzymes

Inactivates drugs, but activates prodrugs

Excretion

Elimination of drug metabolites (mainly) and drugs from the body

Adequate circulation and excretion organ (kidneys, bowels, lungs, skin) function enables

Protein binding

Drugs bound to plasma proteins/carriers (mainly albumins) remain inactive d/t being unable to diffuse through capillaries. However, carriers can store and release drugs PRN

Affects distribution

Pharmacodynamics

Drug action and how it works/makes the body react

Affected by: body comp, genes, immature organs

Agonist

Produces similar effects to naturally occurring hormones, NTs, and other substances, accelerating/slowing normal cellular processes

Antagonist

Inhibits cellular function by occupying receptors

Antidote

Relieves, prevents, or counteracts toxic effects of another drug/poison

Hypersensitivity

An immune-mediated reaction (allergy) to a drug that occurs in pts who have developed antibodies to the drug or to a similar antigen

Serum drug level

Lab measurement of the amount of drug in the blood at a particular time

Reflects: dose, absorption, bioavailability, half-life, and rate of metabolism and excretion

Serum half-life

Time it takes for the serum concentration of a drug to decrease by half

Determined by the drug’s rate of metabolism and excretion

When it’s longer, the f of drug administration decreases

When it’s shorter, the f of drug administration increases

Loading Dose

A beginning dose that’s larger than normal to rapidly increase therapeutic serum drug level

Maintenance Dose

Quantity of drug needed to maintain blood and/or tissue levels stable or constant

Nephrotoxicity

The intra-renal damaging effects of drugs → nephritis/decreased kidney f(x) → decreased GFR → increased drug accumulation and half-life → increased adverse effects

Adverse effects

Unpredictable responses from a drug

Harmful

Call provider

Primary actions

Intended/therapeutic effects

Secondary actions

All other side effects that exclude intended (primary) ones

First-pass effect

When a large amount of oral dose is destroyed upon reaching the liver, before reaching body tissues

Bioavailability

Portion of the dose that reaches systemic circulation and is available to act on body cells

Tyramine-rich (fermented) foods

Should be avoided when on MAO inhibitors d/t the inability to inhibit NE (vasoconstrictor)

1 hour a.c. or 2 hours p.c.

Timing for giving meds to limit drug-diet interactions (can inhibit drug absorption to an extent; drug-drug interactions tend to be more limiting though)

Boxed warning

Serious/life-threatening adverse effects

Alleviating adverse effects

When trying to get a pt to go on new medication while promoting safety, mention:

Activated charcoal

Common OD antidote

Ensure that the unconscious pt’s airway is secure before administering. Laxatives also aid in the removal of the charcoal-drug complex, preventing bowel obstruction

Poison control

Contact when the victim is responsive

911

Contact when the victim is collapsed or not breathing

Blood dyscrasia

Any disorder/abnormality of the blood

Symptoms: Fever, chills, sore throat, back pain, weakness

Anaphylactic shock

Allergic reaction (t1 hypersensitivity)

Symptoms: immediate onset, nausea, paleness, diaphoresis, coughing and wheezing (signifies expiratory obstruction), pruritis (itching), rash, hives (urticaria), dilated pupils, anxiety, rapid HR, respiratory arrest

Antipsychotics

Decreases brain dopamine levels

Secondary actions resemble Parkinson’s d/t that

Side effects: Tremors, drooling, gait changes, restlessness, akathisia, dyskinesia, stiffness

Med error categories

A through I

A is when circumstances have capacity to cause error; I is when the error caused the pt’s death

Diuretics

Black pts respond less to ACE inhibitors and beta-adrenergic blocking drugs when treating heart failure/HTN

Give this instead

Side effects

Predictable responses from a drug

Can be problematic, but NOT Harmful

No need to call provider