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PRINCIPLES > Pharmacology > Flashcards

Pharmacology Flashcards

1
Q

What is the difference between pharmacodynamics and pharmacokinetics?

A

-dynamics: effect of drug on the body (biological effects), -kinetics: effect of the body on the drug (ADME - absorption, desorption, metabolism, excretion)

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2
Q

What is the difference between drugs and medicine?

A

Drugs are chemicals of known structure. Medicines intend to have a therapeutic effect.

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3
Q

What is the difference between selectivity and specificity?

A

Selectivity means able to distinguish. Specificity is absolute selectivity.

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4
Q

What is an agonist?

A

A chemical that binds to a receptor to produce a response

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5
Q

What is an antagonist?

A

A chemical that binds to a receptor and blocks binding of another chemical.

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6
Q

What is the equation for agonism? Give the rate constant names.

A

A + R AR AR*
Where forward reactions are K1 and B
And reverse reactions are K-1 and a

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7
Q

In the agonism equilibrium, there are two steps. What are the names of these? Which rate constants increase them?

A

Affinity and efficacy. K1 and Beta respectively

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8
Q

What is the equation for antagonism? How does it differ from agonism?

A

B + R BR. No efficacy, as no activation required

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9
Q

What is ED50/EC50?

A

The concentration of a drug at which it is half optimal

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10
Q

What is the name for two drugs which have equal EC50 values?

A

Equipotent

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11
Q

Draw the concentration against effect graph for agonism and antagonism. Describe the differences in affinity and potency.

A

View notes. Potency is equal in an agonist and a non-competitive inhibitor, but affinity decreases with the antagonist. Potency is reduced in a competitive agonist, but affinity is constant. Note: LOG units.

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12
Q

Describe the three main types of cell signalling.

A

Autocrine - within own cell. Paracrine - locally (ECF). Endocrine - long distance (vascular)

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13
Q

What are the five main types of receptor?

A

Ligand and voltage gated, GPCRs, kinase-linked, nuclear

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14
Q

Describe how internal nuclear receptors may be activated.

A

Steroids diffuse into cell, bind to response element, form dimer, enter nucleus

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15
Q

Describe the chemical makeup of G protein receptors, and the G proteins themselves.

A

Receptors - 7 alpha helices, with an NH2 and COOH group. G protein - alpha, beta, gamma subunit

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16
Q

How is a G-protein activated?

A

Guanine nucleotide exchange - GDP is replaced by GTP. Units dissociate, until GTP is again hydrolysed to GDP

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17
Q

Describe briefly the adenylyl cyclase GPCR pathway.

A

GPCR activates adenylyl cyclase, which converts ATP to cAMP. cAMP, by PKA, causes intracellular effect

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18
Q

Describe briefly the phospholipase C GPCR pathway.

A

GPCR activates PLC, converts PIP2 into IP3 and DPG. DPG phosphorylates ser/thr amino acids, causing Ca2+ release.

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19
Q

Which two types of drug movement require no energy?

A

Passive/facilitate diffusion - hydrophobic vs channels

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20
Q

Which two types of drug movement require energy?

A

Active transport, endocytosis

21
Q

State the Henderson-Hasselbalch equation.

A

pH = -log(10) [HA]/[A-] + pKa

22
Q

Derive the Henderson-Hasselbalch equation.

A

Key equations: pH = -log[H], pKa = -logKa, Ka = acid dissociation constant
HA H + A. Equilibrium so
Ka = [H][A] / [HA]. Rearrange for [H]
[H] = [HA]Ka / [A]. Sub for pH, separate out Ka
-log[H] = -log[HA]Ka / [A]
pH = -log[HA]/[A] - logKa. Sub in pKa
pH = -log[HA]/[A] + pKa (note change of sign)

23
Q

At which conditions does pH = pKa? Why?

A

When the acid is exactly half dissociated, as [HA][A] = 1, so -log[HA][A] = 0. Refer to Henderson Hasselbalch

24
Q

What is ion trapping?

A

Where a drug gets stuck on one side of a membrane that seperates two different compartments, each with different pH.

25
Q

Why do only weak acids and bases get ion trapped?

A

Weak acids and bases dissociate (partially) into both ionised and unionised forms

26
Q

Use Henderson-Hasselbalch to explain ion trapping.

A

Weak acids ionise at alkaline pHs and vice versa.
If the pH of an environment is acidic, weak acids will remain neutral and weak bases ionised.
If the pH of an environment is basic, weak acids will be ionised and weak bases neutral.
In their ionic form, drugs cannot cross membranes without a channel/active transport, so are trapped.

27
Q

What are the four main body compartments?

A

Oral, plasma, adipose, bone/teeth

28
Q

What is metabolism in the liver?

A

Processing of the drug for removal and to reduce bioavailability in the blood.

29
Q

Describe phase 1 metabolism.

A

Drug is oxidised/reduced/hydrolysed to an active/toxic metabolite, which is then conjugated to be excreted.

30
Q

What is volume of distribution (Vd)?

A

The theoretical volume of drug that would be required to be taken to maintain the distribution through the body.

31
Q

Considering the volume of the body is about 41 litres, which types of drug may be more/less than this for their Vd value and why?

A

> 41 = hydrophobic, < 41 = hydrophillic. Able to diffuse more easily/not as easily

32
Q

What is the formula for Vd? How may its value be clinically determined?

A

Vd = dose/[drug]plasma. [Drug]plasma is calculated by taking a blood sample and centrifugation.

33
Q

Why does an increased Vd decrease [drug]?

A

The drug binds increasingly to plasma protein reducing availability

34
Q

Where does drug secretion principally occur?

A

The kidneys

35
Q

Describe the [drug]plasma spectrum.

A

Too low - sub-therapeutic. Middle - absorption/elimation occur simultaneously. Too high - toxic effects

36
Q

What is the formula for elimination half life?

A

t1/2 = 0.693 x Cl

37
Q

When is drug steady state reached?

A

After about 5 drug half lives

38
Q

Which factors can increase Vd (and hence increase t(1/2)?

A

Decreased muscle mass, increased fluid, obesity

39
Q

Which substance is responsible to clearance in the kidney and how can this have an effect of elimination half life?

A

CP450. Induction reduces, inhibition prolongs

40
Q

What is clearance (Cl)? How is it calculated?

A

Cl = rate of elimination / [drug]plasma. It is a flow parameter.

41
Q

What is the definition of steady state metabolism?

A

When rate of administration = rate of elimination

42
Q

Describe the voltage course of a normal nerve cell depolarisation.

A

Upstroke, overshoot, downstroke, undershoot (back to resting potential)

43
Q

In a nerve cell depolarisation, describe what causes upstroke and what causes downstroke.

A

Upstroke - Na+ channels dominating K+ channels. Downstroke - K+ channels dominating Na+ (which have been inactivated)

44
Q

Describe the neurotransmitters of pre- and post- synaptic ganglia.

A

ALL PRE- are cholinergic (ACh) and then sympathetic post- are NA.

45
Q

What is the name of the type of receptor present between pre- and post-synaptic ganglia?

A

Nicotinic

46
Q

Describe the structure of nicotinic receptors. Which drug can block them?

A

5 subunits. Hexomethonium

47
Q

Describe how neurotransmitters reach their target.

A

Neurotransmitter synthesis -> storage -> wave of depolarisation -> Ca2+ channels open -> exocytosis

48
Q

Which structures degrade noradrenaline?

A

Monoamine oxidase, catechol-o-methyltransferase

49
Q

How is acetylcholine degraded?

A

By acetylcholinesterase, which splits it into acetate and choline for re-uptake into the cell

PRINCIPLES (10 decks)

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