P&i: Basic Pharmacology

Front 1

What are the specific advantages of intravenous drug administration?

Back 1

> Entire dose reaches systemic circulation immediately

> Permits accurate titration

Front 2

What are the specific disadvantages of intravenous drug administration?

Back 2

> Risk of infection

> Increased risk of adverse effects

> Site: requires IV access - overweight patients problematic

> Injections hurt, can cause bruises and frighten children and needle phobics

Front 3

What is the general advantage of parenteral drug administration over oral administration?

Back 3

Parenteral bypasses first-pass metabolism of the hepatic circulation

Front 4

What are the general disadvantages of parenteral administration over oral administration?

Back 4

> Risk of infection

> Injections can cause bruises and pain

> Frightens children and needle phobics

Front 5

What are the specific advantages of intramuscular drug administration?

Back 5

> Good absorption and rapid onset (compared to enteral)

> Straightforward administration

Front 6

What are the specific disadvantages of intramuscular drug administration?

Back 6

> Delayed absorption in shock (blood diverted to organs)

> Site: only certain muscles (deltoid or gluteal)

Front 7

What are the specific advantages of subcutaneous drug administration?

Back 7

> Constant & slow absorption → prolonged effect

> Onset more rapid compared to oral

Front 8

What are the specific disadvantages of subcutaneous drug administration?

Back 8

> Delayed absorption in shock (blood diverted to organs)

> Absorption dependant on blood flow

Front 9

What are the advantages of enteral drug administration?

Back 9

> Safe - reduced risk of adverse effects and infection

> Easy administration - preferred by patients

> Cheapest

> Prolonged action

Front 10

What are the disadvantages of enteral drug administration?

Back 10

> Cannot bypass first-pass metabolism

> Unpredictable absorption due to degradation by stomach acid and enzymes or contents of stomach

> Uncooperative patients may not take them

Front 11

Define bioavailability (F) and the factors that affect it.

Back 11

Fraction of the administered dose of drug that reaches the systemic circulation (F=1 for IV drugs)

Affected by:
First-pass metabolism
Absorption - GI tract disease/abnormality may affect this

Front 12

Define volume of distribution.

Back 12

Apparent volume into which a known amount of drug must be dispersed to give the measured plasma concentration

If you give a dose of a known amount and subsequently measure the drug serum conc., how much the drug has been diluted (how much of the drug is in the blood vs extravascular compartment)?
> Affected by weight of the individual
> the higher the serum conc., the more readily available the drug is for (renal) excretion i.e. ↑ VoD → ↑ half-life

Front 13

Define clearance.

Back 13

Theoretical volume of plasma "cleared" of drug per unit time (e.g. mlmin⁻¹)
Impaired clearance (e.g. ↓ renal function) → drug accumulation

Front 14

Define half-life.

Back 14

The time required for the serum concentration to reduce by half

Determined by clearance and VoD

Takes 4-5 half-lifes for a drug to be excreted: allows you to calculate when a drug will have been fully excreted from the blood i.e. if a patient overdoses on a drug which makes them ill and has a long half-life they will be ill for 4-5x the half life

Front 15

Define steady state and how long it takes to reach.

Back 15

Drug conc. is in dynamic equilibrium: the amount of drug administered is equal to the amount of drug eliminated within one dosing interval (when giving repeated doses)

Takes 4-5 half-lives to reach steady state

Front 16

What is maintenance dosing?

Back 16

The maintenance rate of drug administration equal to the rate of elimination in the steady state

Front 17

Define pharmacokinetics.

Back 17

The science of the rate of movement of drugs within biological systems, as affected by the metabolism, absorption, distribution and elimination of medications

“What your body does to the drug"

Front 18

Define pharmacodynamics.

Back 18

Study of the biochemical and physiologic processes underlying drug action

> Mechanism of drug action

> Efficacy

> Drug-receptor interaction

> Safety profile

“What the drug does to your body"

Front 19

How can you reach steady state quicker than 4-5 half-lives?

Back 19

Give a (large) loading dose - if therapeutic effect is needed more quickly than it takes to reach steady state i.e. for drugs with long half-lifes

Front 20

Describe the difference between the loading dose and maintenance dose in terms of what they are dependent on.

Back 20

Loading dose depends only on the desired drug conc. and the volume of distribution

Maintenance dose depends on drug clearance

Front 21

Define linear pharmacokinetics.

Back 21

Concentration that results from a dose is proportional to the dose

Double the dose, double the concentration

Rate of elimination is proportional to the concentration

50% of a drug will be cleared in one half-life

90% of drugs have linear pharmacokinetics

Front 22

Define non-linear pharmacokinetics.

Back 22

Concentration that results is not proportional to dose

Rate of elimination is constant regardless of amount of drug present

Clinical relevance: side effects are dependent on drug conc. → have to give much smaller doses and monitor for drugs that exhibit NLPKs