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phases of drug action

1) Drug administration 2) Pharmacokinetics 3) Pharmacodynamics

Drug administration

How the dose is made available to the body via a dosage. Form and route.

Pharmacokinetics

Movement of a drug through the body: Absorption, Distribution, Metabolism, Elimination.

Pharmacodynamics

How the drug interacts with receptors to produce its effect

Dosage form

The physical state/formulation of a drug (EX: tablet, liquid, aerosol, patch, etc.).

Inhalation route

Delivery to lungs; can be local (aerosols) or systemic (gases/fine particles).

Systemic effect

Drug reaches bloodstream and affects the whole body.

Localized effect

Drug acts primarily at the application site.

Inhaled gases

typical effect Systemic (e.g., oxygen, heliox).

Inhaled aerosols

typical effect Primarily local airway effect; some systemic absorption possible.

First-pass effect

metabolism of oral drugs before reaching systemic circulation.

Routes that bypass first-pass

IV, IM, subcutanious, intraosseous, sublingual/buccal, inhalation, transdermal, rectal.

Absorption

Movement of drug from administration site into bloodstream.

Distribution

Transport of drug from blood to tissues/sites of action.

Volume of Distribution (Vd)

Apparent volume indicating drug distribution into tissues vs plasma.

Metabolism

primary organ Liver (drug broken down).

Elimination

primary route Renal

Plasma half-life (t½)

the time it takes for the concentration of a substance in the blood plasma to be reduced by half

Receptors

Proteins that bind drugs and alter cell function.

Structure

The Activity Relationship (SAR) Chemical structure influences drug affect

Isoproterenol vs Albuterol

(selectivity) Isoproterenol less selective (β1 & β2); Albuterol β2-selective (fewer cardiac effects).

Agonist

Binds and activates a receptor to produce a response.

Antagonist

Binds without activating; blocks receptor and prevents activation.

Albuterol

β₂-selective → bronchodilation with minimal cardiac effect

Ipratropium

(older, less selective β agonist) → lungs and heart (↑ HR)
reduces bronchoconstriction.

Idiosyncratic response

unusual, unpredictable response to drug

Hypersensitivity

immune-mediated allergic response (may be severe).

Tolerance

Decreased response with repeated use; requires higher doses.

Tachyphylaxis

Rapid, short-term loss of responsiveness after few doses.

MDI

needs coordination; contains propellant

DPI

needs adequate inspiratory flow; uses carrier particles

Nebulizer

useful when coordination/flow is limited; continuous aerosolization.

Particle size & deposition

Larger particles deposit in upper airway (local); fine particles can reach alveoli (systemic).

IV vs Transdermal IV

rapid high peak/short duration of meds; Transdermal = steady lower peak/long duration of meds.

Topical vs Transdermal Topical meds

Topical = local only; Transdermal = designed for systemic effect.

Local inhalation example

Albuterol aerosol targeting bronchial smooth muscle (local bronchodilation).

Systemic inhalation example

Inhaled oxygen/heliox increasing blood oxygen content (systemic).

Pharmacology

The study of drugs.

pharmacy

The preparation and dispensing of drugs

pharmacognosy

Identification of natural drug sources (plants, minerals, animals).

pharmacogenetics

Study of genetic differences in drug responses.

therapeutics

The use of drugs to treat disease

toxicology

The study of harmful effects of drugs.

the five names every drug may have

Chemical, code, generic, official, and trade/brand.

drug name nonproprietary and official

Generic name

drug name appears in official references

Official name

drug name is created for marketing

Trade/Brand name.

USP-NF

United States Pharmacopeia–National Formulary (official U.S. drug standard).

Most common source of drug preparation

Chemical synthesis.

Steps of the U.S. drug approval process

Chemical isolation, animal studies, IND approval (Phases 1–3), NDA submission, post-market surveillance.

Orphan drug

drug developed for a rare disease (<200,000 people in the U.S.) or when cost recovery is not expected.

Main parts of a prescription

Patient info, Rx, inscription, subscription, signature, prescriber info.

What does "Rx" mean

Take thou.

Risk of OTC drugs

Self-treatment can mask or complicate serious conditions.

Phase 1 of IND studies

Small group of healthy subjects (safety).

Phase 2 of IND studies

Small group of diseased subjects (effectiveness).

Phase 3 of IND studies

Large, multicenter studies.

potential ratings A

A = significant therapeutic gain

potential ratings AA

AA = urgent need, fast-track (e.g., AIDS).

potential ratings B

B = modest gain.

potential ratings C

C = little/no gain, but still an option.

Advantages of aerosolized drugs

Smaller dose, fewer side effects, rapid onset, targeted effect, painless/safer

Examples of related drug groups in respiratory care

Antiinfectives, neuromuscular blockers, CNS agents, antiarrhythmics, antihypertensives/antianginals, anticoagulants/thrombolytics, diuretics.

drugs from animals

Thyroid hormone, insulin, pancreatic dornase.

drugs from plants

Atropine, digitalis, reserpine, eucalyptus oil.

drugs from minerals

Copper sulfate, magnesium sulfate (Epsom salt), mineral oil.

PDR

Physician’s Desk Reference.

Major text is known as the "Pharmacological Basis of Therapeutics"

Goodman & Gilman’s.

NDC database

Official registry of drugs.

Aerosol therapy (definition)

Delivery of liquid or powdered medication via inhalation, producing particles suspended in gas.

Aerosol therapy—core uses in respiratory care

Humidify dry gases , mobilize/clear secretions , deliver drugs to the respiratory tract.

penetration

Depth within the lung that particles reach.

deposition

The process which the particles deposit out of suspension to remain in the lung. 

Nebulizers (purpose)

Convert liquid drug solutions or suspensions into aerosols.

Count mode

Most frequently occurring particle size in a distribution.

CMD (Count Median Diameter)

Size dividing 50% of particles by number. (Size of P)

MMD/MMAD (Mass Median Aerodynamic Diameter)

Size dividing 50% of particles by mass. (Weight of Particle)

Why MMAD matters

Better predictor of where drug mass will deposit; guides matching device/drug to target airways.

SIZE Effect of MMAD on site of action

Larger MMAD → more upper-airway deposition; smaller MMAD → deeper lung penetration.

GSD (Geometric Standard Deviation)

Spread of particle sizes (dispersion)

High vs low GSD (concept)

Higher GSD = broader size spread (less uniform deposition); lower GSD = tighter distribution.

FPF (Fine Particle Fraction)

Fraction of particles small enough to reach lower airways.

greater than 10 µm deposition target

Nose and MOUTH

5-10 µm deposition target

More central airways with some throat deposition (first ~6 airway generations).

2-5 µm deposition target

Overall lower respiratory tract (last 5-6 genertions)

0.8-3.0 µm deposition target

terminal airways and alveoli

what is Inertial impaction

filtration mechanimsm - upper airways at higher flow rates; captures larger, denser particles by using their momentum to make them collide with and stick to filter fibers.

what is Sedimentation

filtration mechanimsm - Dominant in mid-to-lower airways; Gravitational Settling

what is Diffusion

filtration mechanimsm- small particles in alveoli. falling out of suspension naturally on their own.

Jet nebulizers—aka

Hand-held nebulizers (HHNs), med-nebs.

Jet nebulizer mechanism

Gas flow creates negative pressure → aerosol