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104 Cards in this Set

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List 4 parenteral routes of administration.
1. Intravenous Bolus (IB)

2. Intravenous Infusion (IV inf)

3. Intramuscular injection (IM)

4. Subcutaneous injection (SC)
Name 3 enteral routes of administration.
1. Buccal or sublingual (SL)

2. Oral (PO)

3. Rectal (PR)
List 2 routes other than enteral and parenteral.
1. transdermal

2. inhalation and intranasal
What is the bioavailability of IV bolus?
Complete, 100%, systemic drug absorption. Rate of bioavailability considered instantaneous.
What are the advantages of IV bolus?
Drug has immediate effect.
List 2 disadvantages of IV bolus?
1. increased chance for adverse rxn

2. possible anaphylaxis
What is the bioavailability of IV inf?
1. complete 100% systemic absorption

2. rate of drug absorption controlled by infusion rate.
What is the bioavailability of buccal or sublingual routes?
Rapid absorption from lipid soluble drugs.
What is an advantage of buccal or sublingual routes?
No "first pass" effects.
What is the bioavailability of the oral route?
Absorption may vary. Generally slower than IV or IM.
What are 2 advantages of the oral route?
1. Safest and easiest route.

2. May use immediate-release and modified-release drug products.
What is the bioavailability of the rectal route?
Absorption may vary from suppository. More reliable absorption from enema (solution).
The rectal route's advantages?
1. Useful when patient can not swallow medication.

2. Used for local and systemic effects.
The bioavailability of the transdermal route?
1. Slow absorption, rate may vary.

2. Increased absorption with occlusive dressing.
List the advantages of the transdermal route.
1. Transdermal delivery system (patch) is easy to use.

2. Used for lipid-soluble drugs with low dose and low MW.
What is the bioavailability of the inhalation and intranasal route?
1. Rapid absorption.

2. Total dose is variable.
What is an advantage of the inhalation and intranasal route?
May be used for local or systemic effects.
Two illustrations of passive diffusion?
1. Fick's Law

2. Henderson-Hasselbach
3 examples of carrier-mediated transport?
1. Intestinal examples

2. Facilitated diffusion

3. Active transport
Describe facilitated diffusion of drug movement?
Carrier mediated, moves along concentraton gradient, requires no energy expenditure.
Describe the active transport of drug movement?
Carrier-mediated and requires energy.
List the 5 general mechanisms of drug movement?
1. Passive diffusion

2. Carrier-mediated transport

3. Vesicular transport

4. Pore transport

5. Ion pair formation
Two examples of vesicular transport.
1. Exocytosis

2. Endocytosis
Give an example of ion-pair formation.
propranolol + oleic acid results in a neutral and so more lipophilic entity
Lipid diffusion will be displayed by an ? molecule.
Lipid diffusion will be displayed by an un-ionized molecule.
Low molecular wt molecules may display what?
Aqueous diffusion
List 3 specialized mechanisms of intestinal absorption.
1. Co-absorption with lipids

2. Active transport

3. Pinocytosis
Describe co-absorption with lipids?
This is a specialized mechanism of intestinal absorption that involves some highly lipid soluble drugs that are absorbed from the gut along with long chain fatty acid and their monoglycerides, fat-soluble vitamins and cholesterol. (ex. griseofulvin)
Describe active transport?
This a specialized mechanism of intestinal absorption that involves some drugs that are similar to nutrients that are naturally actively transported (ex. levodopa and methyldopa are taken up by an amino acid transport system, some anticancer drugs compete with pyrimidines for active transport system)
Describe pinocytosis?
It is a specialized mechanism of intestinal absorption that involves some large MW drugs (ex. the complex of intrinsic factor and vitamin B12) are taken up by pinocytosis.
List 12 general factors affecting gut absorption.
1. pH

2. Area of absorbing surface

3. Dissolved drug concentration

4. GI secretions

5. Bacterial metabolism of drugs.

6. Metabolism during absorption.

7. Clearance after absorption.

8. GI motility

9. Disorders

10. Drug interactions

11. Enteric shunts

12. Food and nutrients
Generally how does the pH of gastric contents affect its absorption?
The pH of gastric contents affects the degree of ionization of a drug and therefore its absorption.
Concerning pH, drugs that are ? than 0.01% ionized are absorbed ? and erratically.
Only slowly and erratically absorbed.
In the STOMACH, what are the pka values of the bases and acids that are hardly absorbed?
In the stomach, bases with pka values of more than 5 and and acids with a pka values of less than 2 are hardly absorbed.
A mucus layer shields the absorption surface from the bulk of the gastric contents.
In the INTESTINES, what are the pka values of the bases and acids that are hardly absorbed?
In the intestines, bases with pka values of more than 8 and acids with pka values of less than 3 are hardly absorbed (except when they have a high Po/w). Basic drugs are too highly ionized to be absorbed in the stomach but are then absorbed in the intestines.
Why does most absorption take place in the small intestine (as opposed to the stomach)?
Because the area of the absorbing surface is larger (about 200m^2 including the microvilli).
A good proportion of a drugs absorption may be absorbed in the intestine because of the surface area size in spite of what?
This might happen even if the pka of a drug favors gastric absorption.
For solid oral dosage forms, what must occur before absorption?
Disintegration and dissolution.
First order absorption process depends on the ? of ? drug.
First order absorption process depends on the concentration of dissolved drug.
The highest concentration of a drug is on a ? stomach.
The highest concentration is on an empty stomach. Lower conc.s are achieved with meals.
What 2 GI secretions may affect gut absorption?
1. Gastric acid

2. Enzymes
Describe how Gastric acid affects gut absorption?
Gastric acid hydrolyzes a number of esters. This results in inactivation for certain drugs or the activation of certain other drugs. (ex. chlorazepate-diazepam)
Describe how enzymes affect gut absorption?
Proteolytic enzymes break up polypeptide drugs (ex. insulin, oxytocin)
Describe how the bacterial metabolism of drugs affect gut absorption?
Commensal bacteria resident in the gut produce enzymes that could act on drugs or drug metabolites. For instance, they act on glucoronide conjugates, the liberated drug moiety may then proceed along the enterohepatic shunt.
Describe some instances of metabolism during absorption that affects gut absorption?
1. SO4 conjugating enzymes present in the intestinal mucosa can cause the inactivation of certain drugs (ex. chlorpromazine) during absorption.

2. AA decarboxylase and monoamine oxidase in the gut mucosa can inactivate part of an orally administered dose of levodopa (used to tx parkinsonism). The rest of the dose can be decarboxylated in the periphery with only 1% entering the brain intact to be converted to dopamine. This is prevented by concomitant administration of the dopa decarboxylase inhibitor carbidopa. (Carbidopa does not enter the brain).

3. Hydrolytic enzymes in the gut mucosa can inactivate glyceryl trinitrate (so given s/l). Hydrolysis of drugs such as ASA and dexamethasone phosphate does not result in loss of pharmacologic activity.
For clearance after absorption (a factor affecting gut absorption) what is the limiting factor for the absorption of lipid soluble drugs?
Blood supply via the sub-mucosal capillaries is the limiting factor for the absorption of lipid soluble drugs.
The faster the removal of a drug from its site of absorption, the greater the what? What does this facilitate?
The faster the removal of a drug from its site of absorption, the greater the concentration gradient. This facilitates absorption either by lipid or aqueous diffusion.
Binding to blood proteins ? the elimination of a drug and ? the concentration of free drug, ? the concentration gradient across the absorption surface. What does this facilitate.
Binding to blood proteins reduces the elimination of a drug and reduces the concentration of free drug, increasing the concentration gradient across the absorption surface. This facilitates absorption.
Concerning GI motility, what do non-propulsive movements do?
They contribute to solid dosage form disintegration and dissolution.
Concerning GI motility, what determines the contact time between dissolved drug and absorbing surface?
Propulsive movements and Transit time.
Explain how propulsive mvmts and transit time may determine the contact time b/n drug and absorbing surface?
1. For drugs that are poorly absorbed from the intestine, drugs that increase contact time (opiate and cholinergics) increase absorption.

2. For drugs that are not absorbed in the stomach, slowing the rate of gastric emptying (eg. by a fatty meal) slows the rate of absorption; stimulating gastric emptying (eg. metoclopramide) increases the rate of absorption.
Some disorders affect gut absorption. Explain how Crohn's disease may do this?
In some patients, Crohn's disease (inflammation of the small intestine and colon) causes a decrease in absorption of certain drugs (eg. trimetoprim) and an increase in the absorption of others (eg. clindamycin).
Some disorders affect gut absorption. Explain how Celiac disease may do this?
In some pts., celiac disease (inflammation of mainly the proximal small intestine) causes a decrease in absorption of certain drugs (digoxin) and an increase in others (eg. clindamycin)
Some disorders affect gut absorption. Explain how achlyrodia may do this?
In aclhyrodia pts (low level of acids in stomach). Weakly basic drugs cannot form soluble salts and so precipitate out. (recall for solid dosage forms solution must proceed absorption)
Some disorders affect gut absorption. Explain how HIV-AIDS may do this?
HIV-AIDS pts show increased gastric transit time, achlorhydia, and diarrhea.
Some disorders affect gut absorption. Explain how CHF may do this?
In CHF pts the reduced bl flow to the gut and reduced intestinal motility result in decreased and/or erratic drug absorption.
Most drug interactions result in what?
Decreased absorption.
What can tetracyclines form? (drug-drug intrxn)
Insoluble chelates can form it tetracyclines (or ciprofloxacin) are administered along with iron preparations or antacids or foods containing polyvalent cations.
How can anticholinergics affect gut absorption? (drug-drug)
Anticholinergics (or drugs with anticholinergic effects) slow gastric emptying and so delay absorption.
How may proton-pump inhibitors affect gut absorption? (drug-drug)
It may render the stomach achlorhydric.
How may non-absorbable ion-exchange resins affect gut absorbtion? (drug-drug)
Non-absorbable ion-exchange resins such as cholestyramine can adsorb other drugs and so reduce their absorption.
Give an example when a drug-drug intrxn actually enhances absorption?
Allopurinol increases iron absorption by inhibiting a limiting transport system.
List some enteric shunts that may affect gut absorption?
1. First-pass effect

2. Enterohepatic shunts

3. Other enteric shunts
- saliva (eg, clonidine)
- gastric juice (quinine)
- Bronchial secretions (bialamicol)
Food can interact ? or ? with a drug.
Food can interact physically or chemically with a drug (esp. if the drug is taken shortly after a meal).
What can fatty foods do the drug absorption?
reduces absorption of certain drugs (viagra) and increases absorption of others (griseofulvin)
What can food do to bile flow?
It can increase bile flow (and result in double peaks).
What can food cause in gastric emptying?
It can cause a delay in gastric emptying (and result in double peaks).
What can food do to the gut pH?
It can change it.
What can food do in the lumen?
It can change the metabolism of a drug in the lumen.
Food can also reduce a drug's ? to the gut mucosa.
Irritation.
How might vit.B-12 affect gut absorption?
VitB-12-intrinsic factor complex is carried to the ileum, it binds to a receptor. There is then a seperation and VitaminB12 gets absorbed.
How might grapefruit juice affect gut absorption?
It inhibits the pre-systemic absorption (gut and/or liver) or certain drugs and so increase their bioavailability.
For sublingual and buccal absorption into circulation is what?
It is direct, this circumvents the possibility of first pass effects.
What molecules are rapidly absorbed by the sublingual route?
Lipid soluble molecules. This is useful for emergency drugs like glyceryl trinitrate and isoprenaline.
How can the absorption of ionizable drugs, generally speaking, be increased?
By suppressing their ionization (like by using a buffer)
Suppositories are solid but soften and melt at ? temperature.
Melt at body temperature.
Drugs absorbed thru the rectal mucosa get into the ? ? and so avoid the ? ? effects.
Drugs absorbed thru the rectal mucosa get into the vena cava and so avoid first pass effects.
Why are enemas subject to first pass effects?
Enemas get into the colon and may reach the ileum and so may be subject to first pass effects.
Vaginal preps are generally intended for what? However, what occurs?
Generally intended for local effects, but absorption thru the vaginal mucosa occurs.
Drugs designed for conjunctival instillation generally act how?
Locally.
Does absorption occur in conjunctival instillation?
To some extent.
Nasal drug delivery could be used for what kind of effects?
Local or systemic.
Nasal mucosa has a rich supply of blood vessels. So what can it deliver?
It can deliver a rapid therapeutic effect.
The lung has a large what?
A large absorption surface.
What do the airways filter?
Inhaled matter to remove foreign material.
What controls the extent to which inhaled material can penetrate the airways?
Droplet size (aerosolization helps) and velocity of application. Devices such as spacers can improve depth of inhalation.
What kind of effects are possible thru the skin?
Both local and systemic.
What kind of drugs penetrate the dermis?
Lipid-soluble drugs.
What kind of drugs cannot penetrate the dermis?
Hydrophilic/ionizable drugs are impeded (unless drived thru by some other means such as electrophoresis).
Why are subq injections more painful?
Because of rich sensory innervation of skin.
Subcutaneous is aka what?
Hypodermic
Would a larger volume be given subq or intramuscular (IM)?
Larger volumes may be give IM.
Following parenteral injections (subq, IM) how is the drug disseminated?
Drug is disseminated after passage thru capillary (MW < 3000 or intermediate) or lymphatic (MW > 20000) endothelium.
What is the MW of parenteral drugs disseminated thru the capillary endothelium?
MW < 3000 or intermediate
What is the MW of parenteral drugs that are disseminated through the lymphatic endothelium?
MW > 20000 or intermediate
Drugs that may otherwise be irritating to tissues may be administered how?
Parenterally (IM, subq)
Besides subq and parenteral IM injections name some other parenteral injections?
1. Intradermal

2. Intraperitoneal

3. Intrathecal

4. Intra-arterial

5. Intracardiac
What are intradermal injections used for?
For test sera.
What are intraperitoneal injections used for?
They are rarely used in man. There is a large absorption area so diffusion into blood is rapid.
Where and why are intrathecal drug administration used?
Given in subarachnoid space for local action on meninges or spinal nerve roots.
What are intra-arterial injections used for?
They are used in animal experiments to localize administration to a specific organ.
What are intracardiac injections used for?
During cardiac surgery when the heart is exposed.
What is the "depot effect"?
When drug effect is prolonged.
List 5 possible causes of the depot effect?
1. By use of vasoconstrictor (like epinephrine)

2. Use of a less soluble salt (like procaine, penicillin, protamine ZN insulin)

3. Use of oil solutions

4. Use of pellets (like steroid hormones)

5. Absorption of a drug onto colloidal surface particles.