Pharmacokinetics I Flashcards by Catherine sendek

How many half-lives does it take to reach steady state concentration or to eliminate the drug?

5 half-lives

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What is the main goal when determining dose?

The goal is to determine the lowest effective dose (~68% of population)

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What factors influence dose?

Maturing organ function (BBB in children)
Age of the patient (decreased kidney
function, increased fat)
Organ pathology (Liver, Kidney, etc.)

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What are other terms for “oral”

Enteral, PO

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What is the most common, convenient, safest and economical method of drug administration?

Oral (enteral, PO)

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What is the main disadvantage of oral drug administration?

First pass effect- the absorbed drug is exposed to the liver first

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When are parenteral routes of administrations used?

Used when drugs cannot be administered orally

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What is the most direct route of administration?

Injections

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How are gaseous anesthetics, agents that readily vaporize, and aerosol drugs administered?

Inhalation

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When is rectal drug administration used?

When oral ingestion is precluded by emesis (vomiting) or unconsciousness

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Does buccal/sublingual drug administration have high or limited first pass effect?

Limited

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Absorption of topical drugs is proportional to what?

The surface area exposed and lipid solubility of the drug

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How do inflammation and conditions that increase cutaneous blood flow effect absorption?

Enhance absorption

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What is absorption?

Process whereby a drug gains entry into bodily fluids, typically the blood, that distribute it throughout the organism.

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Drugs that have a high degree of lipid solubility are most likely absorbed by which mechanism?

Simple diffusion

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What mechanism of absorption do small, water soluble drugs; concentration gradients use?

Aqueous pores

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What mechanism of absorption do drugs use when drugs get engulfed by vesiculation of cell membrane followed by endocytosis?

Vesicular transport

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What factors modify absorption?

Route of administration
Solubility (aqueous vs. oil)
Dissolution
Concentration of drug
Blood flow/Circulation
Absorbing surface area and contact time
pH

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Are most drugs strong acids/ strong bases or weak acids/weak bases?

Weak acids or weak bases

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Are acids proton donators/acceptors?

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Proton donators (HA ↔ A- + H+)

Are bases proton donators/acceptors?

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Proton acceptors (B + H+ ↔ BH+)

What affects a drug’s ability to permeate biological membranes and exert its effect?

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Degree of ionization

To cross a membrane, a drug must be what?

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Non-ionized and lipid soluble

Why are ionized drugs not able to be absorbed?

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Ionized drugs are surrounded by a water molecules that increase
hydrophilicity and prevent it absorption

What kind of acids/bases cannot be absorbed?

Strong acids and bases

An acid in an acidic environment is what?

Non-ionized and readily absorbed

A base in a basic environment is what?

Non-ionized and readily absorbed

What is ion-trapping?

Acid in basic environment or base in acidic environment will become ionized and and will accumulate in that environemnt

When an acid is pronated, is it ionized or non-ionized?

Non-ionized

When a base is pronated, is it ionized or non-ionized?

Ionized

In an acidic environment (stomach), a weakly acidic drug is predominately _____, more lipid soluble and _____ absorbed.

Non-ionized (protonated; HA) | Rapidly

In a basic environment (intestine), a weakly acidic drug is predominately _____, and _____ absorbed.

Ionized (unprotonated; A-) | Not rapidly

In an acidic environment (stomach), a weakly basic drug is predominately _____, and is _____ absorbed.

Ionized (protonated; BH+) | Not rapidly

In a basic environment (intestine), a weakly basic drug is predominately _____, more lipid soluble and _____ absorbed.

Non-ionized (unprotonated; B) | Rapidly

What can ion trapping be used for?

To increase the elimination of drugs

If you make urine basic, ____ drugs will be trapped and excreted. What can you use to make the urine more basic?

Acidic Sodium bicarbonate or acetazolamide

If you acidify the urine, ____ drugs will be trapped and excreted. What can you use to make the urine more acidic?

Basic Ammonium chloride

What does the Henderson-Hasselbalch equation tell you?

Degree of ionization of weakly acidic or basic drug at different pHs

What is pKa?

pH at which the amount of | ionized vs. non-ionized forms of a drug are equal

If pH < pka a) Does the protonated/unprotonated form dominate? b) An acid will be ionized/non-ionized and rapidly/slowly absorbed c) A base will be ionized/non-ionized and rapidly/slowly absorbed

a) Protonated b) Non-ionized (HA), rapidly c) Ionized (BH+), slowly

If pH > pka a) Does the protonated/unprotonated form dominate? b) An acid will be ionized/non-ionized and rapidly/slowly absorbed c) A base will be ionized/non-ionized and rapidly/slowly absorbed

a) Unprotonated b) Ionized (A-), slowly c) Non-ionized (B), rapidly

Weak acid in acidic environment. pKa = 5.4 pH = 4.4 What is A-/HA?

pH < pKa = Protonated dominates More non-ionized (acid + protonated) 1 degree difference = 10 fold A-/HA = 1 ionized/10 non-ionized

Weak acid in basic environment. pKa = 4.4 pH = 7.4 What is A-/HA?

``` pH > pKa = Unprotonated dominates More ionized (acid + unprotonated) 3 degree difference = 1,000 fold ``` A-/HA = 1,000 ionized/1 non-ionized

Weak base in acidic environment. pKa = 5.4 pH = 3.4 What is B/BH+?

``` pH < pKa = Protonated dominates More ionized (base + protonated) 2 degree difference = 100 fold ``` B/BH+ = 1 non-ionized/100 ionized

Weak base in basic environment. pKa = 4.4 pH = 8.4 What is B/BH+?

pH > pKa = Unprotonated dominates More non-ionized (base + unprotonated) 4 degree difference = 10,000 B/BH+ = 10,000 non-ionized/1 ionized

Drug A is a weak organic acid, pKa = 6.4. What is the ratio of ionized to non-ionized drug in the urine with pH = 6.4?

1:1

Drug B is a weak acid, pKa = 6.4. What is the ratio of non-ionized to ionized drug in the blood with pH = 7.4?

``` pH > pka = Unprotonated dominates More ionized (acid + unprotonated) 1 degree difference = 10 fold ``` A- (ionized) / HA (nonionized) = 10/1 HA (nonionized) / A- (ionized) = 1/10 HA/A- ratio = 1:10

Drug B is a weak base, pKa = 5.4. What is the ratio of non-ionized to ionized drug in the blood with pH = 7.4?

pH > pKa = Unprotonated dominates More more non-ionized (base + unprotonated) 2 degree difference = 100 fold B/BH+ ratio = 100:1

Pharmacokinetics I Flashcards

(48 cards)