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Pharmacology > PK1 - Absorption > Flashcards

PK1 - Absorption Flashcards

1
Q

What are the four main pharmacokinetic processes?

A

absorption, distribution, metabolism, elimination

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2
Q

What does pharmacokinetics relate to?

A

How drugs move through, and are altered by the body

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3
Q

What does pharmacodynamics relate to?

A

Mechanisms of drug action

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4
Q

What is the process of absorption?

A

Movement of drug from site of administration into SYSTEMIC circulation

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5
Q

What does bioavailability mean in relation to drugs?

A

The FRACTION of an administered dose of drug that reaches SYSTEMIC circulation UNCHANGED

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6
Q

what is IV bioavailability?

A

100%

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7
Q

What route of administration has the lowest bioavailability and why?

A

Oral is the lowest. Because the liver (which receives drug from GIT) is the major organ for drug metabolism

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8
Q

What is the bioavailability of drugs across the buccal mucosa in cats?

A

It’s virtually complete so ORAL TRANSMUCOSAL bioavailability is nearly 100%

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9
Q

What is the oral bioavailability of buprenorphine?

A

> 70% is metabolized by the liver in ONE pass so the ORAL bioavailability is <30%

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10
Q

What does the rate of absorption affect? (3)

A

onset, duration and intensity of action

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11
Q

What does the onset of effect relate to?

A

It is when the drug reaches the minimum effective concentration for desired effect AFTER administration

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12
Q

What is the duration of action?

A

The length of time the drug effect is within the minimum effective concentration (MEC) for desired effect

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13
Q

What is the peak effect?

A

It is the point that the drug reaches the maximum concentration of intensity within the duration of action

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14
Q

What route of administration has the most rapid absorption?

A

IV administration

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15
Q

What does faster absorption of a drug translate to?

A

faster absorption = faster for patient to feel effects = faster it passes through the organ of elimination = less time it is present in the body

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16
Q

What route of administration has the slowest absorption?

A

subcutaneous administration

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17
Q

What happens if absorption is too slow?

A

If its too slow, the MEC of the desired effect might not be reached. This means there would be no benefit to the patient

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18
Q

What is the difference between ENTERAL and PARENTERAL administration?

A

-Enteral = usually called the ORAL route of administration.
ie. GIT –> portal vein –> liver –> systemic circuation

-Parenteral = routes that involve absorption from other sites than ht GIT so the drug doesnt pass through the liver before getting to systemic circulation (IV, SQ, IM)

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19
Q

What are some advantages of the oral route of administration? (2)

A

-simple; usually the most convenient for at home administration

-usually SAFER than injection (because going to the liver is a safety buffer)

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20
Q

What are some disadvantages of the oral route of administration? (6)

A

-Absorption may be ERRATIC
-Compliance problems (pt and client)
-Not possible if pt is unconscious
-“First Pass” effect (through liver so lose a lot of its effect)
-Too slow for emergency situations
-Emesis and GI irritation possible, might be ineffective in a vomiting pt

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21
Q

What dosing frequency has best compliance from clients?

A

once a day dosing

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22
Q

What is an advantages to sublingual routes of administration? (1)

A

-No first pass metabolism (absorption across oral mucosa into systemic circulation, so it bypasses the GIT)

23
Q

What are some disadvantages to sublingual routes of administration? (2)

A

-Patient must cooperate (don’t swallow drug)
-Significant portion of the dose might be swallowed

24
Q

What drug is well absorbed across oral mucosa?

A

Buprenorphine

25
Q

What are some advantages of the subcutaneous injection route of administration? (3)

A

-Suitable for solid pellets, insoluble suspensions, OILY vehicles
-Safer and easier to administer than IV
-Absorption is SLOWER than by IV or IM routes

26
Q

What are some disadvantages of the subcutaneous injection route of administration? (5)

A

-Not suitable for large volumes
-Pain and necrosis possible with irritating drugs, can be severe
-Absorption can be very SLOW
-Infection possible
-Slow onset of action

27
Q

What are some advantages of the intramuscular injection route of administration? (3)

A

-Absorption is rapid for drugs in aqueous solution
-OILY suspensions form “depot” of drug for slow absorption
-Safer and easier to administer than IV

28
Q

What are some disadvantages of the intramuscular injection route of administration? (3)

A

-Local pain possible even if administered properly; hematoma risk and infection possible
-Not suitable for large volumes
-Pain or necrosis possible with irritating drugs, can be severe

29
Q

What are some advantages of the intravenous BOLUS injection route of administration? (4)

A

-Rapid onset of activity, good for emergencies
-Suitable for LARGE volumes
-Irritating drugs become diluted as injection into bloodstream proceeds, but must inject SLOWLY
-100% bioavailability

30
Q

What are some disadvantages of the intravenous BOLUS injection route of administration? (4)

A

-Higher risk of adverse effects
-Often must inject slowly due to CARDIAC TOXICITY RISK
-Not for oily/insoluble drugs. Can lead to embolism
-Requires more SKILL

31
Q

What are some advantages of the intravenous CONSTANT RATE injection route of administration? (3)

A

-Suitable for large volumes
-Safest route for irritating drugs as they become diluated. but can damage vessel if given too fast
-Delivered directly into systemic circulation –> bioavailability is 100%

32
Q

What are some disadvantages of the intravenous CONSTANT RATE injection route of administration? (2)

A

-INFECTION risk from catheter
-Requires more skill

33
Q

What is considered the topical route of administration

A

Ears, eyes, skin, mucous membranes, vagina, colon, urethra, etc

34
Q

What are some advantages of the topical route of administration? (2)

A

-Drug can be delivered to SITE OF NEED
-can achieve very high concentration

34
Q

What are some disadvantages of the topical route of administration? (2)

A

-May be absorbed systemically
-May not remain in place and can be messy

35
Q

What is transdermal administration?

A

Drug that is applied to the skin with the intention of having it absorbed into SYSTEMIC CIRCULATION to produce an effect elsewhere in the body

36
Q

What are some advantages of the transdermal route of administration? (1)

A

-Controlled release with prolonged duration of action (fentanyl patches)

37
Q

What are some disadvantages of the transdermal route of administration? (3)

A

-Slow ONSET of action
-Excessive absorption may occur if blood flow to skin is excessive (could lead to toxic concentrations achieved in systemic circulation)
-Absorption through damaged skin is enhanced

38
Q

What does drug “formulation” refer to? (2)

A

-Can either be the physical form of the medication (like tablet, liquid for IV, etc) OR can be the chemical ingredients in a pharmaceutical

39
Q

What type of solubility to un-ionized molecules have?

A

They are more lipid soluble so they can diffuse across membranes

40
Q

What type of solubility to ionized molecules have?

A

They are more water soluble so they can diffuse through the cytoplasm, ECF, etc

41
Q

How does a molecule flip between ionized and un-ionized?

A

Flips by binding to or unbinding from hydrogen ions (protons)

42
Q

What determines the proporation of molecules that are ionized?

A

the pKa.

=pH at which 50% of the drug molecules are IONIZED

43
Q

What is the pH range for drug pKa values?

A

usually between pH 3-11
-acetaminophen = pKa of 9.5
-aspirin = pKa of 3.5

44
Q

When do the un-ionized forms of acids and bases predominate?

A

AH and BH+ forms predominate when drug enters envrionment rich in protons

pH < pKa (left)

45
Q

When do the ionized forms of acids and bases predominate?

A

A- and B forms predominate when drug enters environment poor in protons

pH > pKa (right)

46
Q

Will a weakly acidic drug with a pKa of 4.4 be better absorbed from the stomach (pH = 1.4) or from the intestine (pH = 6.4)?

A

Stomach

47
Q

Will a weakly basic drug with a pKa of 4.4 administered orally be better absorbed from the stomach (pH = 2.4) or from the small intestine (pH = 6.4)?

A

small intestine

48
Q

What happens to weak acids/bases in the stomach when they are taken orally?

A

They become protonated in the stomach.

A- + H+ –> AH
B + H+ –> BH+

49
Q

What form are most oral drugs and why?

A

Most oral drugs are weak acids because protonated acids arent ionized and are therefore readily absorbed

50
Q

Where do basic drugs accumulate? Acidic drugs?

A

-Basic drugs = acidic fluids
-Acidic drugs = basic fluids

51
Q

What determines degree of ionization

A

Tissue pH

52
Q

Where does drug accumulation occur?

A

Drugs accumulate on the side of the membrane where ionization is highest

Pharmacology (22 decks)

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