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Top 100 Drugs > Mechanisms of Action > Flashcards

Mechanisms of Action Flashcards

1
Q

5α-reductase inhibitors

finasteride

A

5α-reductase reduces testosterone to active metabolite dihydrotestosterone

Dihydrotestosterone stimulates prostatic growth

So 5α-reductase inhibitors reduce size of prostate gland by inhibiting this

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2
Q

α-blockers

doxazosin, tamsulosin, alfuzosin

A

Drugs in this class are highly selective for α1-adrenoreceptors

α1-adrenoreceptors are found in smooth muscle e.g. vessels + urinary tract

Stimulation of receptors induces constriction
Blockade of receptors induces relaxation

α1-blockers therefore cause vasodilation, ↓ BP and reduced resistance to bladder outflow

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3
Q

Acetylcholinesterase inhibitors

donepezil, rivastigmine

A

Acetylcholine is important CNS neurotransmitter (learning + memory)

These drugs inhibit cholinesterase enzymes which break down acetylcholine in CNS

By increasing availability of acetylcholine, these drugs improve cognitive function + slow rate of decline

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4
Q

Acetylcysteine (N-acetylcysteine)

A

Paracetamol is normally metabolised by conjugation with glucuronic acid and sulfate

Small amount of NAPQI is produced (hepatotoxic) - quickly detoxified by conjugation with glutathione

In poisoning, body’s glutathione is overwhelmed, NAPQI is left free to cause liver damage

Acetylcysteine replenishes body’s supply of glutathione

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5
Q

Activated charcoal

A

Van der Waals forces

Molecules are aDsorbed onto surface of charcoal as they travel through gut, reducing their aBsorption into circulation

Weakly ionic, hydrophobic substances adsorbed best (e.g. benzodiazepines, methotrexate)

Can also increase elimination of certain poisons - multiple doses used to maintain steep conc. gradient of poison to encourage diffusion out of circulation

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6
Q

Adenosine

A

Agonist of adenosine receptors on cell surfaces

In heart, activation of these receptors induces several effects:

  • Reducing frequency of spontaneous depolarisation
  • Increasing resistance to depolarisation

This transiently slows sinus rate and conduction velocity

Increasing AV node refractoriness

Increased refractoriness in AV node breaks the re-entry circuit, which allows normal depolarisations from SA node to resume control of heart rate (cardioversion)

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7
Q

Adrenaline

epinephrine

A

Potent agonist of α1, α2, β1, β2

α1: vasoconstriction of skin and mucosa vessels

β1: increased heart rate and contractility and excitability

β2: vasodilation of coronary vessels and bronchodilation plus suppression of inflammation mediator release from mast cells

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8
Q

Aldosterone antagonists

spironolactone, eplerenone

A

Mineralocorticoid

Acts on mineralocorticoid receptors in distal tubules of kidney - increases activity of luminal epithelial Na channels (ENaC)

This increases reabsorption of Na and water, elevates BP, increases secretion of K

Aldosterone antagonists competitively bind causing Na and water EXCRETION and K RETENTION

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9
Q

Alginates and antacids

gaviscon, peptac

A

Antacids: buffer stomach acids

Alginates: Increase viscosity of stomach contents to reduce reflux - form “floating raft” separating gastric contents from gastro-oesophageal junction

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10
Q

Allopurinol

A

Xanthine oxidase inhibitor

Xanthine oxidase is enzyme which metabolises xanthine from purines → uric acid

So drug lowers plasma uric acid

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11
Q

Aminoglycosides

gentamicin, amikacin, neomycin

A

Work mainly on Gram -ve aerobic bacteria

Inhibit 30S ribosome subunit irreversibly

Enter bacteria through oxygen dependent transport system

Penicillins weaken cell wall and so may enhance aminoglycoside activity by increasing bacterial uptake

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12
Q

Aminosalicylates

mesalazine, sulfasalazine

A

Ulcerative Colitis:
Release 5-ASA which seems to have anti-inflammatory and immunosuppressive effects
Act topically on gut rather than systemically so preparations delay release of active ingredient until reaching colon

Rheumatoid Arthritis:
Sulfapyridine is probably active component, mechanism unclear

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13
Q

Amiodarone

A

Blockade of Na, Ca, K channels

Antagonism of α- and β-adrenergic receptors

Reduces spontaneous depolarisation, slows conduction velocity and increases resistance to depolarisation, including in AV node

Reduces ventricular rate in AF and atrial flutter (by interfering with AV node)

May break re-entry circuit and restore sinus rhythm in SVT

Options for treatment and prevention in VT

Improves chances of successful defibrillation in refractory VF

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14
Q

ACE inhibitors

ramipril, lisinopril, perindopril

A

Block ACE to prevent conversion of angiotensin I to angiotensin II

Angiotensin II is a vasoconstrictor + stimulates aldosterone secretion

Inhibition therefore causes ↓ BP

Dilates efferent glomerular arteriole so slows progression of CKD

Reducing aldosterone level promotes Na and water excretion so reduces preload

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15
Q

Angiotensin receptor blockers

losartan, candesartan, irbesartan

A

Block action of angiotensin II on angiotensin type 1 receptor

Angiotensin II = vasoconstrictor, stimulates aldosterone secretion, constricts efferent arteriole

ARBs = opposite effect

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16
Q

Antidepressants

tricyclics; amitriptyline, lofepramine

A

Inhibit reuptake of noradrenaline and 5-HT from synaptic cleft, thereby increasing their availability for neurotransmission

Block a wide array of receptors (muscarinic, histamine, α-adrenergic and dopamine) therefore have extensive side effects

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17
Q

Antidepressants

venfalaxine, mirtazapine

A 
Venlafaxine = SNRI
Mirtazapine = antagonist of pre-synaptic α2-adrenoreceptors

Both drugs increase availability of monoamines for neurotransmission

Venlafaxine is weaker antagonist of muscarinic and histamine receptors than tricyclics

Mirtazapine is portent agonist of histamine (NOT muscarinic) receptors so commonly causes sedation

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18
Q

Antiemetics - dopamine D2-receptor antagonists

metoclopramide, domperidone

A

Nausea + vomiting triggered by a wide arrange of stimuli that all converge in “vomiting centre” in medulla (this receives input form chemoreceptor trigger zone, solitary tract nucleus, vestibular system and higher centres)

D2 receptor is main receptor in chemoreceptor trigger zone (CTZ) which senses emetogenic substances in blood - therefore D2RAs are good for nausea caused by CTZ stimulation (e.g. drugs)

D2 is important in gut where it promotes relaxation of stomach and LOS , and inhibits gastroduodenal coordination - therefore D2RAs have prokinetic effect → gastric emptying which contributes to antiemetic action in conditions with reduced gut motility (e.g. due to opioids)

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19
Q

Antiemetics - histamine H1-receptor antagonists

cyclizine, cinanrizine, promethazine

A

Nausea + vomiting triggered by a wide arrange of stimuli that all converge in “vomiting centre” in medulla (this receives input form chemoreceptor trigger zone, solitary tract nucleus, vestibular system and higher centres)

Histamine and acetylcholine (muscarinic) receptors predominate in the vomiting centre and its communication with the vestibular system

H1RAs block both receptors and are therefore useful in a wide range of conditions, particularly when associated with motion/vertigo

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20
Q

Antiemetics - serotonin 5-HT3-receptor antagonists

ondansetron, granisetron

A

Nausea + vomiting triggered by a wide arrange of stimuli that all converge in “vomiting centre” in medulla (this receives input form chemoreceptor trigger zone, solitary tract nucleus, vestibular system and higher centres)

High concentration of 5-HT3 receptors in the CTZ responsible for sensing emetogenic substances in the blood (e.g. drugs)

5-HT is key neurotransmitter released by gut in response to emetogenic stimuli

It stimulates the vagus nerve, which in turn stimulates vomiting centre via solitary tract nucleus

Effective against N+V as a result of CTZ stimulation (drugs) and visceral stimuli (gut infection, radiotherapy) but NIOT motion sickness

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21
Q

Antifungal drugs

nystatin, clotrimazole, fluconazole

A

Fungal cell membranes contain ergosterol, human cells do not, therefore it is a target for antifungals

Polyene antifungals (nystatin) bind to ergosterol in cell membrane, creating polar pore which allows intracellular ions to leak out, killing/slowing growth of fungi

Imidazole (clotrimazole) and triazole (fluconazole) fungals inhibit ergosterol synthesis, impairing cell membrane synthesis and cell growth + replication

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22
Q

Antihistamines - H1-receptor antagonists)

cetirizine, loratadine, fexofenadine, chlorpgenamine

A

Antagonism of H1 receptor, which blocks the effects of excess histamine:

Increased capillary permeability causing oedema

Vasodilation causing erythema

Nasal irritation

Sneezing

Rhinorrhoea

Congestion

Conjunctivitis

Itch

Urticaris

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23
Q

Antimotility drugs

loperamide, codeine phosphate

A

Loperamide is an ggonist of opioid receptors in gut

Increases non-propulsive contractions of gut smooth muscle, but reduces propulsive (peristaltic) contractions

Transit of bowel contents is slowed and anal sphincter tone is increased

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24
Q

Antimuscarinics - bronchodilators

ipratropium, tiotropoium, glycopyrronium, aclidinium

A

Bind to muscarinic receptor and competitively inhibit acetylcholine

Stimulation of muscarinic receptor brings about parasympathetic/”rest and digest” effects

In blocking the receptor, antimuscarinics have the opposite effects:

Increase HR and conduction

Reduce smooth muscle tone (inc. resp tract and bladder)

Reduce secretions from gland in resp and GI tracts

Relaxation of pupillary constrictor + ciliary muscles in eye

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25
Q

Antimuscarinics - cardiovascular and GI uses

atropine, hyoscine butylbromide, glycopyrronium

A

Bind to muscarinic receptor and competitively inhibit acetylcholine

Stimulation of muscarinic receptor brings about parasympathetic/”rest and digest” effects

In blocking the receptor, antimuscarinics have the opposite effects:

Increase HR and conduction

Reduce smooth muscle tone and peristaltic contraction (including GU tract)

Reduce secretions from resp tract and gut

Relaxation of pupillary and ciliary muscles in eye

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26
Q

Antimuscarinics - GU uses

oxybutynin, tolterodine, solifenacin

A

Bind to muscarinic receptor and competitively inhibit acetylcholine

Promotes bladder relaxation

Reduces urinary frequency, urgency and urge incontinence

Through antagonism of the M3 receptor

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27
Q

Antipsychotics - 1st generation (typical)

haloperidol, chlorpromazine, prochlorperazine

A

Block post-synaptic dopamine D2 receptors

Incompletely understood mechanism

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28
Q

Antipsychotics - 2nd generation (atypical)

quetiapine, olanzapine, risperidone, clozapine

A

Block post-synaptic dopamine D2 receptors

Incompletely understood mechanism

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29
Q

Antiviral drugs

aciclovir

A

HSV1 & 2 contain double-stranded DNA

This requires herpes-specific DNA polymerase for the virus to replicate

Aciclovir enters herpes-infected cells and inhibits the herpes-specific DNA polymerase

Inhibiting further viral DNA synthesis & replication

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30
Q

Antiplatelet drugs - ADP-receptor antagonists

clopidogrel, ticagrelor, prasugrel

A

Prevent platelet aggregation

Bind irreversibly to adenosine diphosphate (ADP) receptors on surface of platelets

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31
Q

Antiplatelet drugs

aspirin

A

Irreversibly inhibits COX to reduce production of pro-aggregatory factor thromboxane form arachidonic acid

Reducing platelet aggregation

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32
Q

Azathioprine

A

Pro-drug

Main metabolite is 6-mercaptopurine

Metabolites inhibit synthesis of purines and therefore inhibit DNA and RNA replication

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33
Q

β-blockers

bisoprolol, atenolol, propanolol, metoprolol, carvedilol

A

Reduce force of contraction and speed of conduction in the heart

Relieves myocardial ischaemia by reducing cardiac work and oxygen demand

Slow ventricular rate in AF by prolonging refractory period of the AV node

Reduce hypertension through variety of mechanisms including reducing renin secretion from kidneys

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34
Q

β2-agonists

salbutamol, terbutaline, salmeterol, formoterol, indacaterol

A

B2 receptors found in smooth muscle of gut, bronchi, uterus and vessels

Stimulation leads to smooth muscle activation

Improves airflow in constricted airways

Stimulates Na/K/ATPase pumps, causing shift of K from extracellular to intercellular compartment

Useful adjunct in hyperkalaemia

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35
Q

Benzodiazepines

diazepam, temazepam, lorazepam, chlordiazepoxide, midazolam

A

Target is the GABAa receptor - a chloride channel that opens in response to binding by GABA

Opening channel allows chloride to flood in, making the cell more resistant to depolarisation

Benzos facilitate and enhance binding of GABA to GABAa receptor

Wide depressant effect - reduced anxiety, sleepiness, sedation, anticonvulsion

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36
Q

Bisphosphonates

alendronic acid, disodium pamidronate, zoledronic acid

A

Reduce bone turnover by inhibiting action of osteoclasts (cells responsible for resorption)

Bisphosphonates accumulate in osteoclasts where they inhibit activity and promote apoptosis

Reduction in bone loss and improved bone mass

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37
Q

Calcium and vitamin D

calcium carbonate, calcium gluconate, colecalciferol, alfacalcidol

A

Calcium homeostasis is controlled by parathyroid hormone and vitamin D (which increase serum calcium and bone mineralisation) and calcitonin (which reduces serum calcium)

In osteoporosis, calcium + vit D may reduce rate of bone loss

In CKD there is hyperphosphataemia and hypocalcaemia

In hyperkalaemia, calcium raises myocardial threshold potential, reducing excitability and risk of arrhythmias

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38
Q

Calcium channel blockers

amlodipine, nifedipine, dilitiazem, verapamil

A

Decrease calcium entry into vascular and cardiac cells, reducing intracellular calcium concentration

Causing relaxation and vasodilation in arterial smooth muscle

In heart, CCBs reduce myocardial contractility

Suppress cardiac conduction, slowing ventricular rate

Reduced cardiac rate, contractility and afterload reduce myocardial oxygen demand, preventing angina

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39
Q

Carbamazepine

A

MoA incompletely understood

Appears to inhibit neuronal sodium channels

Stabilising resting membrane potentials and reducing neuronal excitability

40
Q

Cephalosporins and carbapenems

cefalexin, cefotazime, meropenem, ertapenem

A

Bactericidal effect is due to their beta-lactam ring

Cephalosporins and carbapenems inhibit enzymes responsible for cross-linking peptidoglycans in bacterial cell walls

This weakens cell walls, resulting in bacterial cell swelling, lysis and death

41
Q

Chloramphenicol

A

Binds to bacterial ribosomes, inhibiting protein synthesis - bacteriostatic

Stops bacterial growth, allowing immune system to clear microorganisms

42
Q

Corticosteroids (glucocorticoids) - inhaled

beclometasone, budesonide, fluticasone

A

Pass through plasma membrane and interact with receptors in the cytoplasm

Activated receptor then passes into nucleus to modify transcription of genes

Downregulate pro-inflammatory interleukins, cytokines and chemokines

Upregulate anti-inflammatory proteins

Reducing mucosal inflammation, widening airway and reducing mucus secretion

43
Q

Corticosteroids (glucocorticoids) - systemic

prednisolone, hydrocortisone, dexamethasone

A

Mainly glucocorticoid effects

Bind to cytosolic glucocorticoid receptors which then pass into nucleus and bind to glucocorticoid-response elements which regulate gene expression

Modify immune response

Upregulate anti-inflammatory proteins

Downregulate pro-inflammatory genes (cytokines, TNF alpha)

44
Q

Corticosteroids (glucocorticoids) - topical

hydrocortisone, betamethasone

A

Immunosuppressive, metabolic and mineralocorticoid effects

45
Q

Digoxin

A

Negatively chronotropic (reduces heart rate)

Positively inotropic (increases force of contraction)

In AF and flutter it involves increased vagal (parasympathetic) tone

Reduces conduction at AV node, thereby reducing ventricular rate

In heart failure, inhibits Na/K/ATPase pumps, causing Na to accumulate in cell - increasing contractile force

46
Q

Dipeptidylpeptidase-4 inhibitors

sitagliptin, linagliptin, saxagliptin

A

Incretins (GLP-1 and GIP) are released by intestine throughout the day, particularly in response to food

They promote insulin secretion and suppress glucagon release, lowering blood glucose

Incretins are rapidly inactivated by hydrolysis by DPP-4

DPP-4 inhibitors (gliptins) therefore lower blood glucose by preventing incretin degradation and increasing plasma concentrations of their active forms

Actions of incretins are glucose dependent, occurring when blood glucose is elevated

47
Q

Direct oral anticoagulants (DOACs)

apixaban, dabigatran, edoxaban, rivaroxaban

A

Act on final common pathway of the coagulation cascade - comprising factor X, thrombin and fibrin

Apixaban, edoxabab, rivaroxaban directly inhibit activated factor X (Xa), preventing conversion of prothrombin to thrombin

Dabigatran directly inhibits thrombin, preventing conversion of fibrinogen to fibrin

All DOACs therefore inhibit fibrin formation, prevention clot formation

48
Q

Loop diuretics

furosemide, bumetanide

A

Act on loop ascending limb of Henle, where they inhibit the Na/K/Cl co-transporter

This enzyme is responsible for transporting ions from lumen into epithelium, and water then follows via osmosis

Inhibiting this process has a potent diuretic effect

Also have a direct effect on vessels, causing dilation of capacitance veins

In heart failure this reduces preload and improves contractile function of overstretched heart muscle

49
Q

Thiazide and thiazide-like diuretics

bendroflumethiazide, indapamide, chlortalidone

A

Inhibit the Na/K/Ca co-transporter in the distal convoluted tubule of the nephron

Prevents reabsorption of sodium and its osmotically associated water

Resulting diuresis causes an initial fall in extracellular fluid volume

50
Q

Dopaminergic drugs for Parkinson’s disease

levodopa as co-careldopa/co-beneldopa, ropinirole, premipexol

A

In Parkinson’s there is a deficiency of dopamine in the nigrostatial pathway

Treatment seeks to increased dopaminergic stimulation to the striatum

Dopamine does not cross the blood-brain-barrier

Levodopa is a precursor of dopamine that can enter via a membrane transporter

Ropinirole and pramipexol are relatively selective agonists for the D2 receptor in the striatum

51
Q

Emollients

aqueous cream, liquid paraffin

A

Help replace water content in dry skin

Contain oils/paraffin-based products that help soften skin and reduce water loss by protecting against evaporation from skin surface

52
Q

Fibrinolytic drugs

alteplase, streptokinase

A

Catalyse conversion of plasminogen to plasmin

Which acts to dissolve fibrinous clots and re-canalise occluded vessels

53
Q

Gabapentin and pregablin

A

Structurally related to GABA, however do not bind with GABA receptors

MoA is not completely understood

Seems to be mediated through binding with pre-synaptic voltage-sensitive calcium channels

This inhibits release of excitatory neurotransmitters

Resulting in reduction of neuronal excitability

54
Q

H2-receptor antagonists

ranitidine

A

Reduce gastric acid secretion

Acid normally produced by protein pump which secretes H+ into stomach lumen - regulated by histamine

Blocking H2-receptors therefor blocks acid secretion

55
Q

Heparins and fondaparinux

enoxaparin, dalteparin, fondaparinux, unfractioned heparin

A

Antithrombin inactivates clotting factors, particularly factors IIa (thrombin) and Xa

Heparins and fondaparinux act by enhancing the anticoagulation effect of antithrombin

56
Q

Insulin

insulin aspart, insulin glargine, biphasic insulin, soluble insulin

A

Diabetes:
Stimulates glucose uptake from circulation into tissues + increases use of glucose as energy source

Hyperkalaemia:
Drives potassium into cells (short term)

57
Q

Iron

ferrous fumarate, ferrous sulfate

A

Aim is to replenish iron stores

58
Q

Lamotrigine

A

MoA incompletely understood

Binds to voltage-sensitive neuronal channels, interfering with Na influx into neuron

Impedes repetitive neuronal firing, which is a characteristic of seizure activity

59
Q

Laxatives - osmotic

lactulose, macrogol, phosphate enema

A

Based on osmotically active substances that are not digested/absorbed

Hold water in the stool, maintaining the volume and stimulating peristalsis

Lactulose also reduces ammonia absorption

60
Q

Laxatives - stimulant

senna, bisacodyl, glycerol suppositories, docusate sodium

A

Increase water and electrolyte secretion from colonic mucosa

Thereby increasing volume of colonic content and stimulating peristalsis

61
Q

Leukotriene receptor antagonists

montelukast

A

In asthma, leukotrienes produced by mast cells and eosinophils activate the G-coupled protein receptor CysLT1

This activates a cascade of pathways that result in inflammation and bronchoconstriction

LRAs block the CysLT1 receptor, dampening the inflammatory cascade

62
Q

Levetiracetam

A

Molecular target is SV2A which is expressed throughout the brain

presumably through interfering with synaptic vesicle function, levetiracetam modulates neuronal excitability and reduces risk of seizures

63
Q

Lidocaine

A

Enters cells in uncharged form, then accepts a proton to become charged

Enters and blocks voltage-gated Na channels

This prevents initiation and propagation of APs in nerves and muscle, inducing local anaesthesia

In the heart, it reduces the duration of APs, slows conduction velocity and increases the refractory period

64
Q

Macrolides

clarithromycin, erythromycin, azithromycin

A

Inhibit bacterial protein synthesis

Bind to the 50S subunit of bacterial ribosome and block translocation, a process required for elongation of the polypeptide chain

Inhibition of protein synthesis is bacteriostatic (stops bacterial growth), which allows immune system to kill + remove bacteria from the body

65
Q

Metformin

A

Lowers blood glucose by reducing hepatic glucose output (glycogenolysis and gluconeogenesis)

Does not stimulate insulin secretion + therefore does not induce hypoglycaemia

Cellular mechanisms involve activation of AMP kinase

66
Q

Methotrexate

A

Inhibits dihydrofolate reductase, which converts dietary folic acid to tetrahydrofolate (FH4)

FH4 is required for DNA and protein synthesis, so lack of it prevents cellular replication

Actively dying cells are particularly sensitive to methotrexate, hence its use in cancer

Also has anti-inflammatory and immunosuppressive effects

67
Q

Metronidazole

A

In anaerobic bacteria, reduction of metronidazole generates a nitrosio free radical

This binds to DNA, reducing synthesis and causing widespread damage, DNA degradation and cell death

68
Q

Naloxone

A

Binds to opioid receptors where it acts as a competitive antagonist

Little or no effect in the absence of an exogenous opioid

If opioid is present, naloxone displaces it from its receptors and in doing so reverses its effects

69
Q

Nitrates

isosorbide mononitrate, glyceryl trinitrate

A

Nitrates are converted to NO

NO increases cGMP synthesis and reduces intracellular Ca in vascular smooth muscle cells, causing them to relax - vasodilation

Relaxation of venous capacitance vessels, reduced cardiac preload and left ventricular filling

This reduces cardiac work and myocardial oxygen demand, relieving angina and heart failure

70
Q

Nitrofurantoin

A

Metabolised in bacterial cells by nitrofuran reductase

Its active metabolite damages bacterial DNA and causes cell death

71
Q

NSAIDs

naproxen, ibuprofen, etoricoxib

A

Inhibit prostaglandin synthesis from arachidonic acid by inhibiting COX

Therapeutic benefits are principally mediated by COX 2 inhibition

E.g. inhibiting prostaglandins that cause inflammation and pain

72
Q

Ocular lubricants - artificial tears

hypromellose, carbomers, liquid and white soft paraffin

A

Soothing effect

Protect eye surface from abrasive damage

Electrolyte solutions with high viscosity

73
Q

Oestrogens and progestogens

combined ethinylestradiol products, desogestrel

A

Suppress LH/FSH release and hence ovulation

74
Q

Opioids - strong

morphine, oxycodone

A

Activation of opioid receptors in CNS

Reduce neuronal excitability and pain transmission

In medulla, blunt response to hypoxia and hypercapnoea, reducing respiratory drive

Reduce sympathetic nervous system (fight/flight) activity

75
Q

Opioids - weak/moderate

tramadol, codeine, dihydrocodeine

A

Metabolised in liver to produce relatively small amounts of morphine (from codeine) or dihydromorphine (from dihydrocodeine)

These metabolites are stronger agonists of opioid receptors, and account for most of the analgesic effect

76
Q

Oxygen

A

Increases PO2 in alveolar gas

Driving more rapid diffusion of oxygen into blood

Increases delivery of oxygen to tissues

Accelerates diffusion of nitrogen out of the body

In CO poisoning: competes with CO to bind with haemoglobin and thereby shortens half-life of carboxyhaemoglobin

77
Q

Paracetamol

A

MoA poorly understood

Weak inhibitor of COX

COX inhibition appears to increase pain threshold and reduce prostaglandin E2 concentrations in thermoregulatory receptors in hypothalamus, controlling fever

78
Q

Penicillins

(benzylpenicilin, phenoxymethylpenicillin)

(piperacilllin with tazobactam - tazocin)

(amoxicillin, co-amoxiclav)

A

Inhibit enzymes responsible for cross-linking peptidoglycans in bacterial cell walls

This weakens cell walls, preventing them from maintaining an osmotic gradient

Uncontrolled entry of water into cell causes cell swelling, lysis and death

Penicillins contain beta-lactam ring, which is responsible for their bactericidal activity

79
Q

Penicillins - penicillinase-resistant

flucloxacillin

A

Inhibit enzymes responsible for cross-linking peptidoglycans in bacterial cell walls

This weakens cell walls, preventing them from maintaining an osmotic gradient

Uncontrolled entry of water into cell causes cell swelling, lysis and death

Penicillins contain beta-lactam ring, which is responsible for their bactericidal activity

Flucloxacillin has an acyl side chain which protects the beta-lactam ring against beta-lactamases, which are enzymes made by bacteria to deactivate penicillin

This makes flucloxacillin effective against beta-lactamase-producing staphylococci

80
Q

Phosphodiesterase (type 5) inhibitors

sildenafil

A

Phosphodiesterase inhibitor

Selective for PDE-5 that is found in smooth muscle of corpus cavernosum of penis and arteries of lung

For an erection to occur, stimulation is required - this releases NO which stimulates cGMP production causing arterial smooth muscle relaxation, vasodilation and penile enlargement

As PDE-5 is responsible for breakdown of cGMP, inhibition of this by sildenafil increases cGMP concentrations, improving penile blood flow and erection quality

Similar mechanisms in pulmonary vasculature

81
Q

Prostaglandin analogue of eye drops

latanoprost, bimatoprost

A

Glaucoma usually associated with elevated intraocular pressure

Lowering intraocular pressure reduces glaucoma progression

Prostaglandin analogues reduce intraocular pressure by increasing outflow of aqueous humour via uveoscleral pathway

82
Q

Protein pump inhibitors

lansoprazole, omeprazole, pantoprazole

A

Reduce gastric acid secretion

Irreversibly inhibit H/K-ATPase in gastric parietal cells

This is the proton pump responsible for secreting H+ and generating gastric acid

83
Q

Quinine

quinine sulfate

A

Thought to act by reducing excitability of motor end plate in response to acetylcholine stimulation, reducing frequency of muscle contraction

84
Q

Quinolones

ciprofloxacin, moxifloxacin, levofloxacin

A

Kill bacteria by inhibiting DNA synthesis

85
Q

Serotonin 5HT1-receptor agonists

sumatriptan

A

Relieve symptoms of acute migraine

Triptans constrict cranial blood vessel and inhibit neurotransmission in peripheral trigeminal nerve and trigeminocervical complex

86
Q

Sex hormone antagonists for breast cancer

tamoxifen, anastrozole, letrozole

A

2/3s of breast cancers express oestrogen receptors

Oestrogen binds to these and stimulates cell proliferation

Sex hormone antagonists reduce tumour cell proliferation by blocking effects of oestrogen

Tamoxifen is a selective oestrogen receptor modulator which prevents oestrogen binding to its receptor

Aromatase inhibitors interfere with synthesis of oestrogens outside the ovary

87
Q

Statins

simvastatin, atorvastatin, pravastatin, rosuvastatin

A

Reduce serum cholesterol levels

Inhibit 3-hydroxy-3-methyl-glytaryl coenzyme A reductase (enzyme involved in making cholesterol)

Decrease cholesterol production by the liver and increase clearance of LDL from blood

88
Q

Sulphonylureas

glicazide

A

Lower blood glucose by stimulating pancreatic insulin secretion

Block ATP dependent K channels in pancreatic beta-cell membranes, causing depolarisation of cell membrane and opening Ca channels

This increases intracellular Ca concentrations, stimulating insulin secretion

89
Q

Tetracyclines

doxycycline, lymecycline

A

Inhibit bacterial protein synthesis

Bind to ribosomal 30S subunit found specifically in bacteria

This prevents binding of transfer RNA to messenger RNA, which prevents addition of new amino acids to growing polypeptide chains

Bacteriostatic - stops bacterial growth allowing immune system to kill and remove bacteria

90
Q

Thyroid hormones

levothyroxine, liothyronine

A

Thyroid produces thyroxine (T4) which is converted to more active triiodothyronine (T3) in target tissues

Thyroid hormones regulate metabolism and growth

Levothyroxine is synthetic T4 - used for long-term replacement of thyroid hormones

Liothyronine is synthetic T3, has a shorter half-life and quicker onset and offset - therefore reserved for emergency treatment of severe/acute hypothyroidism

91
Q

Trimethoprim

trimethoprim, co-trimoxazole

A

Bacteria are unable to use external sources of folate so need to make their own for essential functions e.g. DNA synthesis

Trimethoprim inhibits bacterial folate synthesis, slowing bacterial growth (bacteriostasis)

92
Q

Valproate (valproic acid)

sodium valproate, valproic acid

A

MoA incompletely understood

Appears to be weak inhibitor of neuronal sodium channels, stabilising resting membrane potentials and reducing neuronal excitability

Increases brain content of GABA, which regulates neuronal excitability

93
Q

Vancomycin

A

Inhibits growth and cross-linking of peptidoglycan chains, inhibiting synthesis of the cell wall of Gram-positive bacteria

Thus lysing and killing the bacterial (bactericidal)

94
Q

Vitamins

folic acid, thiamine, hydroxocobalamin, phytomenadione

A

Organic substances required ins mall amounts for normal metabolic processes

In pregnancy and preconception period, folic acid reduces risk of congenital neural tube defects

95
Q

Warfarin

A

Warfarin inhibits hepatic production of vitamin K-dependent coagulation factors (factors II, VII, IX and X, and proteins C and S)

It does this by inhibiting vitamin K epoxide reductase, the enzyme responsible for restoring vitamin K to its reduced form

96
Q

Z-drugs

zopiclone, zolpidem

A

Similar MoA to benzodiazepines

Target is the GABAa receptor, a chloride channel that opens in response to binding by GABA

Opening the channel allows chloride to flow into the cell, making the cell more resistant to depolarisations

Z-drugs facilitate and enhance binding of GABA to the GABAa receptor

This has widespread depressant effect on synaptic transmission

Resulting in reduced anxiety, sleepiness and sedation

Top 100 Drugs (4 decks)

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