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Pharmacology > 1.2 Pharmacodynamics > Flashcards

1.2 Pharmacodynamics Flashcards

1
Q

What is PD

A

Effects drug has on body & MOA

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2
Q

How do drugs exert effects

A
  1. Phsyiochemical properties
  2. Enzyme inhibition
  3. Receptor activation
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3
Q

Physiochemical examples

A

Anatacids - alter ph & neutralise acid
Mannitol - osmotic diueresis
Act charcola - adsborbs ingest poison
Penicillamine - chelating - red conc metal ion chelating

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4
Q

Enzyme

A

Protein catlyse reaction not used up in reaction
Specic sub & sens ph & temp

Increases conc of substate, decrease product reaction

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5
Q

Example enzymes

A

Aspirin - COX inhib = inhib txa2 & inhib further plat aggreg & vcon

ACE - inhib I - II, also prevents BK bdown
reduce Ang II, side effects cough
Neostigmine - reversible inhbi achesterase

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6
Q

Receptors that alter Ion permeability

Ach

Bzd

A

Cell membrane span complex - potential form channel
Ligand bind - opens = allow passage ion down conc grad

2 ach molec @ 2 alpha sub unit ach rec - ion channel @ NMJ
Rapid increase sodium pasaghe - membrane depol

BZD - gaba/a
Channel - cl ion
Hyperpolisation

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7
Q

Reducing ion permeability

A

Ketamine - NMDA - reduced perm receptor
Glut & glyc b ind = ion chnaell Ca ion allow pass & signal conducted
Ketamine bind - antagonise - closed channel & inhib Ca ion

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8
Q

Intermed messengers eg

Ex act

A

Gpro couple:
B-agonist - increase cAMP - inotropy
Opiates

TKR:
Insulin
GF

GC:
ANP
NO

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9
Q

Gpro couple receptor

A

Membrane protein
Serpentine structure, cross 7 times

Ligand - ex cell side - act grpo on cytsol side - imed messenger = change
Metabotrophic

Provide ampification - intracell messenger resued after stimulus
can be high potent

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10
Q

What are Gproteins

A

Heterotrimeric pro
Mediate change

A, B Y subunit
Called G Pro - a sub bind gdp & gtp

inactive - a sub - bind gdp 
Ligand bind & act gdp exchanged for gtp
aGTP subunit dissoc form B-Y dimer & activate / inhib effect intra cell protein
normal cAMP (rarely phsopC)

Effector - a subunit act GTPase & bdown to regent inactive gdp subunit
Rejoin B & Y subunit to hetortimer complex

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11
Q

Types gproteins

A

Gs
Gi
Gq

Gs - a sub stim AC - increase cAMP - effect

Gi - a sub inhib AC - red cAMP

Gq - Phosph C
control bdown of phsopino -> IP3 & DAG
Ip3 - calcium - membrane hyper pol/enz rel
DAG- pro kin c

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12
Q

Examples gpro interaction

A

A1 adrenergic agon -Gq = act PL C = inc IP3 & DAG

A2 & Opiates - Gi = red AC & cAMP = red Ntmission

B1 - Gs increase cAMP & contraction

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13
Q

PDI

A

Phosphodiesterase inhib
cAMP - gpro bdown by phosopdi
Inhib prevent bbreakdown cAMP - action prolonged
Aminopyline & milrinone

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14
Q

Insulin

A

2 a & 2b
Cell embrane - b tranverse
Insulin bind a - act phosp -> tyrosine in b sub in cell
active phosphhroltaion targ protein
Reduce intracell effects
Glut 4 molecules on membrane - increase uptake

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15
Q

Gene transcription regulator

A

Steroid & throyid hormone

Cytoplsam - steroid bind, complex move nucles - transcriptase & alter prod

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16
Q

Drug interactions

A 
Response to drug modfy action other drug
1 increase or decrease by second
Incompatibility
PK Interaction
PD interaction
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17
Q

Pharmaceutical incompat

A

2 drugs chem/phys imcpm - mix & 1 complex & activate

Thop & sux 1 syringe

Metab posion - chelate chem & remove gi / cir
Pencillamine - metal posin/wilsons

Payaldhyde glass syirnge

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18
Q

PK interaction

A

ADME

Charcoal - toxic in pos

Prokinetic - alter GIT

muscarinic - inhib emptying - oppostie

Distrib - CO increase red speec absorb
BBloq - red co sux longer NMJ

COmpeter site - enzyme syst
Phenytoin w/ sulphonamide - displace pheny

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19
Q

Metabolism of the following drugs are affected by the acetylator status of the individual:

A 
hydralazine
isoniazid
sulphonamides
phenelzine
dapsone, and
procainamide.
20
Q

Agonist

A

affinity for a receptor and has intrinsic efficacy

21
Q

Intrinsic efficacy /activity

A

Intrinsic efficacy or activity describes the capacity of a drug-receptor interaction to produce a maximal response.

22
Q

Antagonists

A

Antagonists have equal affinity for a receptor but no intrinsic efficacy.

23
Q

Partial agonists

receptor occupancy & dose response curve?

A

Partial agonists have equal affinity for a receptor but partial intrinsic efficacy. If receptor occupancy of a full agonist is plotted against response and then compared with a dose response curve, the functional response lies to the left. This suggests that low receptor occupancy can produce a full response.

24
Q

Rate elim

A

Rate of elimination can be described by the following equation:

C = C^0. e-kt

25
Q 
Context-sensitive half lives after eight hours:
Remi
propofol
alfentanil
thio
fentanyl
A

Context-sensitive half life is the time taken for the plasma concentration of a drug to fall by 50%, after the cessation of infusion designed to maintain a steady state plasma concentration.

Remifentanil - 5 minutes
Propofol - 40 minutes
Alfentanil - 50 minutes
Thiopental - 150 minutes
Fentanyl - 250 minutes.
26
Q

Agonist react causes -

Most abundant second messenger is
Located in

A

When an agonist interacts with a receptor on the cell surface, second messengers relay signals to target molecules in the cytoplasm or nucleus. They also amplify the strength of the signal. Calcium is the most ubiquitous and abundant second messenger that regulates multiple cellular functions in the body.

These include:

Muscle contraction (skeletal, smooth and cardiac)
Exocytosis (neurotransmitter release at synapses and insulin secretion)
Apoptosis
Cell adhesion to the extracellular matrix
Activation of lymphocytes
Biochemical changes mediated by protein kinase C.
cAMP is either inhibited or stimulated by G proteins.

27
Q

IP3 and DAG are the second messengers for

A

angiotensin and thyroid stimulating hormone.

28
Q

The receptors in the body that G stimulating (Gs) increase cAMP include:

A 
Beta (β1, β2, and β3)
Dopamine (D1 and D5)
Histamine (H2)
Glucagon
Vasopressin (V2).
cGMP is the second messenger for the action of nitric oxide (NO) and atrial natriuretic peptide (ANP).
29
Q

The therapeutic index

A

The therapeutic index in humans is the toxic dose50 for 50% of the population (TD50) divided by the minimum effective dose50 for 50% of the population (ED50).

The therapeutic index in animals is the lethal dose50 for 50% of the population (LD50) divided by the minimum effective dose50 for 50% of the population (ED50).

30
Q

Additive interaction

A

Additive interaction (summation) (1 + 1 = 2)

The actions of combinations of intravenous agents such as ketamine and thiopentone or ketamine and midazolam are described as additive. They have different mechanisms of action. Ketamine is an NMDA receptor antagonist whereas thiopentone and midazolam are GABAA receptor agonists. Another example is nitrous oxide and halothane.

31
Q

Synergism

A

Synergism (supra-additive interaction) (1 + 1 >2)

Refers to the administration of two drugs with similar pharmacological properties and closely related sites of action that produces an effect in combination that is greater than would be expected from the summation of the contribution of each component. These can be interpreted and understood by construction of an isobologram. The hypnotic effect of benzodiazepines and intravenous induction agents such as propofol is the best example. Midazolam is often administered prior to propofol as part of a co-induction technique.

32
Q

Potentiation

A

Potentiation

Volatile agents potentiate the effects of neuromuscular blocking agents in a dose dependent manner. Effects of the neuromuscular blocking agents can be increased by electrolyte disturbance (hypermagnesaemia), Penicillin and probenecid (the latter has no similar pharmacological activity).

Infra-additive interaction (antagonism) (1 + 1 <2)

33
Q

Michaelis menten kinetics

How is it initially
first or zero

A

Michaelis-Menten kinetics describes the reaction of substrate (S) and enzyme (E) to form product (P), via an enzyme substrate complex (ES).

The kinetics are saturatable and therefore are initially first order (rate is proportional to substrate concentration), becoming zero order (rate independent of substrate concentration, that is, constant rate) as the enzyme’s active sites become occupied.

34
Q

What is Km

A

The constant Km is the concentration of substrate at half maximal reaction velocity, that is, ½Vmax (not Vmax). The equation may be applied to drug absorption, elimination and distribution.

An enzyme is a protein based catalyst, and as defined it is not consumed by the reaction it catalyses.

35
Q

Plasma cholinesterase metab what

A

Sux
mivac
ester LA

Diamorphine - pro drug - converted active by esterase

Nestogmine
hydrl cholinester

36
Q

Messenger systems
a1
m3

A

Gq - plc/ip3/dag = increase calcium

37
Q

a2
opiates
adenosine
dopamine d2

A

Gi

inhib AC

inhib camp

38
Q

B1
b2
dopa d1
2nd mssgr

A

Gs

Increase AC

Incr CAMP

39
Q

NO messenger

A

stim GC +
cgmp

= red ca

40
Q

Insulin

A

stim TKr

reduce camp

41
Q

PDEi

A

inhib pde

increase camp
cgmp

42
Q

Clerance drug liver - depends of enzme activity if

A

if hepatic extraction ratio small

43
Q

renal clearance - how

if drug is unionised =

Why alter urinary pH

A

filtration and secretion
if drug uni - pass freely into tubules
clearnce reduce

why alter ph urine - % alter uni - absorbed - clerance drug altered

Aspirin and alkaline urine

44
Q

Distribution

warfarin

Of all highly protein bound drug low?

passage monamine across bbb

more cross placenta or bbb

A

Warfarin low d/t high protein binding

not case for all highly protein bound
eg propofol 98% prot bound but highly distrib
d/t dynamic nature protein binding

negligible across bbb - contain MAoxidase

placetna
affected fetus ph
pethidine - more ionised in lower fetal pH = ion trapping

45
Q

context sensitive half time

A 
Time
Plasma drug conc
to halve
after cessation contin infusion
Designed maintain constant concentration

may be very diff to drug elim half time

High if conductance ratio is high

prop 20min after 2h

remi is fairly constant

46
Q

VD highest between lido warf roc paracet

A

Lidocaine
.7-1.5l kg

warfarin - .14lkg

roc .2-.3

paracetamol .9
<20% prot bind

pen
.5-.6l kg

Pharmacology (15 decks)

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