PK PD Flashcards

1
Q

what is PK and PD

A

Pharmacokinetics (PK): How the body processes the drug

Pharmacodynamics (PD): How drugs affect the body

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2
Q

Secondary PK Parameters:

A
  1. Elimination half life (t1/2)
    * t1/2= ln(2) x V/CL
  2. Elimination Rate constant (k)
    * k=CL/V
  3. Fraction excreted unchanged (fe)
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3
Q

Primary PK Parameters:

A

1. Clearance (CL)
Volume of plasma from which a substance is completely removed per unit time (L/h, L/h/kg)
* Proportionality constant between the rate of drug elimination and the drug concentration (-dA/dT=CL x C)

2. Volume of Distribution (V)
* Apparent volume into which the drug is distributed to provide the same concentration as it is currently is in blood plasma (L/kg)

3. Bioavailability(F)
* The rate and extent to which the active ingredient or active moiety is absorbed from a drug product and becomes available at the site of action

4. Absorption rate constant (ka)
* The fractional rate of absorption. Rate of absorption = ka x Aa (amount of drug present in the compartment)
* Affected by blood flow at absorption site, exercise, etc

5. Distribution rate constant (kT)
* kT=(Q/VT)/KPb (See rate of distribution)

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4
Q

PK parameters whose values depend on primary PK parameters and dose of drug

A

Area under curve (AUC) (Dose/CL)
Cmax (Dose/V)
Amount excreted unchanged

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5
Q

3 ways of transport across membrane

A
  1. passive transcelllular
  2. facilitated transcellular
  3. paracellular
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6
Q

different drusg ahve different pk profiles in individuals.
PK profile is affected by

A

Physicochemical properties (Polarity, Lipophilicity, Acidic/basic, Molecular weight)
PK properties (% metabolised, % renally cleared, % binding, High/low Eh, Large/small V)
Route of administration

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7
Q

what law for passive diffusion

A

ficks law of diffusion

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8
Q

what affects absorption rate?

A

physiochemical factors(size, lipophilicity, charge, solubility)
physiological factors(total absorptive area, blood flow, permeability, transporters, drug metabolising enzyme)

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9
Q

factors that affect bioavailability

A

AUC
CL
Dose

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10
Q

Rate limited Gi absorption

A

dissolution&raquo_space; absorption
dissolution &laquo_space;absorption

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11
Q

enteric coat purpose

A

protects from stomach acid

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12
Q

BCS(biopharmaceuticals classification system)

A

class 1: high sol, high per
class 2: low sol, high per
class 3: high sol, low per
class 4: low sol, low per

most drugs in class 1 and 2

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13
Q

usually ka is slower or faster than k

ka is absorption rate while k is elimination rate

A

ka»k

if it goes the other way, its the flip-flop phenomeneme

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14
Q

physiological factors that affects distribution

A
  1. membrane characteristics (thickness and porosity)
  2. carrier-mediated transport
    * equilibrating transporters
    * concentrating transporters
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15
Q

how to calculate V?

A

V = Dose(mg)/Co

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16
Q

is there a way to measure appareatness?

A

Kp: tissue to plasma equilibrium distribution ratio (Ct/C)

V = Vp + VtKp