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Pharmacology 1 > Pharmacotherapeutics > Flashcards

Pharmacotherapeutics Flashcards

1
Q

Explain Repeat administration:

A
  • if a drug that is eliminated by first-order kinetics is administered repeatedly (e.g one tablet every 8 hours), the average plasma concenration of the drug will increase until a mean steady-state level is reached.
  • (this will not occur for drugs that exhibit zero-order elimination)
  • the interval of time required to reach steady state is equal to five half-lifes
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2
Q

What is Steady state?

A
  • steady state designates an average plasma concentration and the range of fluctations above and below that level.
  • some fluctuation in plasma concentration will occur even at steady state. levels will be at high point of the steady state range shortly after a dose is administered; levels will be at the low point immediately before administration of the next dose.
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3
Q

The magnitude of fluctuations in Steady State can be controlled by?

A
  • by the dosing interval. A shorter dosing interval decreases fluctuations, and a longer dosing interval increases them.
  • on cessation of multidose administration, 94-97% of the drug will be eliminated in a time interval equal to five half-lives if forst order kinetics applies.
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4
Q

What is the mean of plasma concentration during Steady-state?

A
  • Cpss is 1.44 times higher then the Cmax after the first application.
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5
Q

Calculation of average plasma concentration during steady-state:

A
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6
Q

Explain the Loading dose?

A
  • A large loading dose may be needed initially when the therapeutic concentration of a drug in the plasma must be avhieved rapidly (e.g a life threatening situation in which one cannot wait for 5 half-lives for the drug to reach the desired steady-state level)
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7
Q

How to calculate the Loading dose:

A
  • select the desired plasma concentration of drug and multiply by the Vd
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8
Q

What is the next step after administration of the loading dose?

A
  • After administration of the loading dose (ehich rapidly achieves the desired plasma concentration of drug), one administers the drug at the maintenance dose rate to maintain the drug concentration at the desired steady-state level
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9
Q

What is the “ Amount of drug in Body”?

A

AB = Cp x Vd

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10
Q

What is the dose requested for the initiation of the therapy?

A
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11
Q

Explain the fundamental relationship of Amount of drug in Body and the initiation of therapy: How to remain at steady-state

A
  • To remain at steady-state, the dose rate must equal the elimination rate; that is, the rate at which the drug is added to the body must equal the rate at which it is eliminated.
  • The elimination rate = Cl + Drugplasma
  • Because the dose rate must equal the elimination rate to be at steady state, dose rate also equals: Dose rate = Cl x Desired Drugplasma
  • If one administers a drug at the maintenace dose rate, a steady state plasma concentration of drug will be reached in 4 to 5 half-lives.
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12
Q

What are the Maintenance dose rate?

A
  • It is the dose of a drug required per unit time to maintain a desired steady-state level in the plasma to sustain a specific therapeutic effect.
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13
Q

How do you determine the dose rate required to maintain an average steady-state plasma concentration of a drug?

A
  • multiply the disired plasma concentration by the CL:
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14
Q

Factors influencing drug action

  • Species, subspecies and bloodlines - Receptorial:
A
  • Cattle: Xylazine
  • Cat: Morphine
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15
Q

Factors influencing drug action

  • Species, subspecies and bloodlines - Absorption:
A
  • Horse: Ampicillin
  • Horse and Rabbit: Atropine
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16
Q

Factors influencing drug action

  • Species, subspecies and bloodlines - Distribution:
A
  • Dog: Ivermectin
17
Q

Factors influencing drug action

  • Species, subspecies and bloodlines - Metabolism:
A
  • Cat: Salycilates, Phenols,
  • Dog: Sulphonamides
  • Pig: Procaine
  • Rabbit and Goat: Atropine
18
Q

Factors influencing drug action

  • Species, subspecies and bloodlines - Gut flora:
A
  • Rabbit, hamster: Penicillin
19
Q

Factors influencing drug action:

A
  • Species, subspecies, bloodlines
  • Health status, condition
  • dosage
  • Route of application (MgSO4, Insulin)
  • feeding
  • gender/sex
  • Age
  • tolerance
  • dependence, abuse
  • idiosyncrasy
  • allergy - alaphylaxis
20
Q

Factors influencing drug action:

  • Health status, condition
A
  • Fever: reduced emptying of stomach, negative effect on absorption
  • Diarrhoea: increased gut motility, decreased bioavailability. Exsiccation -> altered distribution, decreased urinary excretion
21
Q

Factors influencing drug action:

  • Dosage
A
  • Atropine: antimuscarinic < pre-anaesthetic < antidote
  • Xylazine: week sedation, mild analgesia < deep sedation, strong analg.
22
Q

Factors influencing drug action:

  • Feeding
A

(type and composition of feed)

  • Decreased bioavailability (Ca2+ –> antibiotics)
  • Increased activity of metabolising enzymes (plant-steroids)
23
Q

Factors influencing drug action:

  • Gender/sex
A
  • In males the metabolism could be faster (testosterone is a CYP3A inductor), LD50 values may be higher - this is not always true.
24
Q

Factors affecting Drug Disposition and Responses in Elderly:

  • Absorption
A
25
Q

Factors affecting Drug Disposition and Responses in Elderly

  • Body composition and Protein binding
A
26
Q

Factors affecting Drug Disposition and Responses in Elderly:

  • Metabolism and Excretion
A
27
Q

Factors influencing drug action:

  • Tolerance
A

(according to multiply application)

  • Subjects reaction to a drug decreases
  • the organism builds up a resistance to the effects (receptor regulation, altered metabilism)

–> Tachyphylaxis is the rapid development of drug tolerance

–> Drug immunity (body is totally insensitive against drug “ab ovo”)

28
Q

Factors influencing drug action:

  • Dependence, abuse
A

(according to multiply application)

  • Habituation - force of habit, mental, not real psychological
  • addiction - strong psychological and frequently physiological
29
Q

Factors influencing drug action:

  • Idiosyncrasy
A

(single, first application)

  • individual hypersensitivness, serious symptoms, hereditary (e.g doberman against Phenylbutazone)
30
Q

Factors influencing drug action:

  • Allergi reaction
A

(According to multiply application)

  • Allergi reaction is an uncommon and unwanted side effect og medication, less than 10% og adverse drug (human) reactions are allergic.
  • like most allergies, a drug allergy is caused by an over-sensitive immune system.
  • A allergic reaction does not often happen the first time patient takes a medication. A reaction is much more likely to occur the next time taking that medication
31
Q

Types of medicines that can cause allergic reactions:

A

Antibiotics, hormones, anticonvulsants, NSAIDs

32
Q

Factors maintaining drug allergy:

A
  • contamination of skin
  • inhalation, contamination of airways
  • depot preparations
  • chronic diseases, atopy
33
Q

Allergic reactions ca be subdivided into four types:

A
  • Type 1: immediate or anaphylactic reaction
  • Type 2: Cytolytic
  • Type 3: immune complex associated
  • Type 4: Delayed or cellular
34
Q

Type 1, Immediate or anaphylactic reaction:

A

IgE on the receptors of mass cells or basophile leucocytes + allergens

  • Histamine, prostaglandings, leukotrienes
  • vasodilation, oedema, inflammation

–> diarrhea, urticaria (hives), atopic dermatitis, Rhinitis, asthmatic seizure

  • eliination of clinical signs is rapid!!
35
Q

What is the difference between Anaphylaxis and Anaphylactoid reactions?

A
  • Anaphylaxis: refers to a systemic, immediate hypersensitivity reaction due to he IgE-mediated release of mediators from mast cells and basophils.
  • Anaphylactoid: refers to a clincally similar event NOT mediated by IgE. They cause via an unknown mechanism.
36
Q

Type 2, Type 3 and Type 4 allergic reactions:

  • Mechanism and examples of adverse reactions
A

Pharmacology 1 (12 decks)

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