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Pharmacology MBBS > Histamine, serotonin and eicosanoids > Flashcards

Histamine, serotonin and eicosanoids Flashcards

1
Q

Types of histamine receptors

A
  1. H1: Gq
  2. H2: Gs
  3. H3: Gi pre synaptic
  4. H4: Gi on leukocytes
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2
Q

Effects of H1 receptor

A 
Gq ➡️ increases Ca
1. Bronchoconstriction
2. Vasodilation: NO (produced by Ca dependent endothelial NOS)
3. GIT: contraction
4. Hypothalamus:
 Anorexia
 Wakefulness
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3
Q

Effects of H2 receptor

A

Gs ➡️ increases cAMP

  1. Myocardial contraction
  2. Increased acid secretion in stomach
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4
Q

Effects of H3 receptors

A

Gi ➡️ stimulates H3 receptors ➡️
Decreases histamine release ➡️
decreases effect of H1 and H2
H3 blockers/ inverse agonists are used

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5
Q

Effects of H4 receptor and the drugs affecting this receptor

A

Gi - chemotaxis
Present in leukocytes
Drugs: H4 blocker
Used in atopic dermatitis

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6
Q

H3 blockers/ inverse agonists

A

Examples:
Tiprolisant
Pitolisant
They increase histamine ➡️ H1 stimulation ➡️ increased wakefulness ➡️ treatment of narcolepsy

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7
Q

First generation H1 blockers

A 
Anti-muscarinic effects
Reduced potency
Lipid soluble ➡️ crosses BBB ➡️ side effects: sedation
CI:
1. Drivers
2. Pilots
3. Children
4. Elderly people
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8
Q

Second generation H1 blockers

A

Increased potency
Lipid insoluble: do not cross BBB
Less sedating
Preferred in drivers and pilots

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9
Q

Examples of first generation H1 blockers

A
  1. Promethazine: anti-emetic
  2. Diphenhydramine: local anaesthetic
  3. Dimenhydrinate: insomnia
  4. Doxylamine: morning sickness
  5. Chlorpheniramine
  6. Hydroxyzine: anti-pruritic, anxiolytic
  7. Doxepin: TCA
  8. Cyprohepadine
  9. Meclizine/cyclizine: motion sickness
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10
Q

Promethazine, diphenhydramine and dimenhydrinate

A

First generation H1 blocker
Maximum antimuscarinic effect
Uses: treatment of
1. EPS (Extra pyramidal side effects) like acute dystonia and Parkinsonism
2. Motion sickness: 1hr before travel (oral)
3. Ménière’s disease

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11
Q

Promethazine specific properties and uses

A

First generation H1 blocker (,anti muscarinic) and α1 blocker ➡️ causes hypotension
Uses:
1. In chemotherapy induced nausea and vomiting
2. As local anaesthetic

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12
Q

Specific uses of diphenhydramine and dimenhydrinate

A 
Both are first generation H1 blocker
Diphenhydramine:
 As local anaesthetic
Dimenhydrinate:
 For treatment of insomnia
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13
Q

Doxylamine

A

First generation H1 blocker

DoC for morning sickness (used with vitamin B6)

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14
Q

Chlorpheniramine

A

Least sedating 1st generation H1 blocker ➡️

Day time use

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15
Q

Hydroxyzine, cetirizine and levocetirizine

A 
Hydroxyzine:
1. First generation H1 blocker 
2. Anti pruritic effect ➡️ used in skin allergy
3. Anti emetic
4. Anxiolytic
Cetirizine:
1. 2nd generation H1 blocker
2. Metabolite of hydroxyzine 
3. Most sedating 2nd generation drug
Levocetirizine: 
1. more potent derivative of cetirizine 
2. 3rd generation H1 blocker
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16
Q

Doxepin

A

First generation H1 blocker

Used as TCA (Tricyclic antidepressant)

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17
Q

Cyprohepadine

A

First generation H1 blocker

Used as 5HT2 blocker, muscarinic blocker

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18
Q

Meclizine/cyclizine

A

First generation H1 blocker

Treatment of motion sickness, though less effective

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19
Q

2nd generation H1 blockers example

A
  1. Cetirizine
  2. Astemizole: not used
  3. Terfenadine: not used
  4. Loratidine: bronchodilator
  5. Rupatadine: anti-inflammatory
  6. Acrivastine: nasal decongestant
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20
Q

Astemizole, terfenadine and fexofenadine

A

First 2 are 2nd generation H1 blockers
Astemizole and Terfenadine:
QT prolongation
Not used now

Fexofenadine:
Derivative of terfenadine (used)
Least sedating H1 blocker
Substrate for P glycoprotein in brain ➡️ efflux

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21
Q

Loratidine

Acrivastine

A

Both are 2nd generation H1 blocker
Loratidine:
For prophylaxis of exercise induced bronchoconstriction

Acrivastine:
Used along with pseudoephedrine as a nasal decongestant

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22
Q

Rupatadine

A

2nd generation H1 blocker
Inhibits PAP (platelet activating factor) ➡️
anti inflammatory effect

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23
Q

Topical H1 blockers

A
  1. Alcaftadine
  2. Azelastine: AR
  3. Epinastine
  4. Olopatidine: AR
  5. Ketotifen
  6. Levocarbastine
    All are used for: allergic conjunctivitis and ocular pruritis
    Azelastine and Olopatadine: used for allergic rhinitis
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24
Q

3rd generation antihistaminics

A

Derivatives of 2nd generation antihistaminics

  1. Levocetirizine
  2. Fexofenadine
  3. Desloratidine (most potent H1 blocker)- derivative of loratidine
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25
Q

Uses of H1 blocker

A 
1. Allergic rhinitis (hay fever):
 DoC: steroid
 Antihistaminic of choice: 2nd generation H1 blocker
2. Non allergic rhinitis:
 1st generation H1 blocker 
 (anti muscarinic effect ➡️ decreased secretion)
3. Urticaria:
 DoC: 2nd generation antihistaminics
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26
Q

Bradykinin synthesis

A

Kininogens ➡️ kallikrein (intermediate) ➡️ kallidin and bradykinin,
both stimulate bradykinin receptors B1R and B2R, leading to:
1. Increased synthesis of PG ➡️ pain and inflammation
2. Increased synthesis of NO ➡️ vasodilation

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27
Q

Bradykinin related drugs

A 
Against hereditary angioedema
Blocker of B2R:
 Icatibant: treatment
Kallikrein antagonists:
1. Aprotinin 
2. Lanadelumab: prophylaxis 
3. Ecallantide: treatment
Aprotinin (inhibits plasmin) to reduce risk of bleeding on CABG patients
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28
Q

Hereditary angioedema

A 
1. Treatment:
 DoC: C1 esterase inhibitor
Alternatives: icatibant, ecallantide
2. Prophylaxis:
 DoC: Danazol 
 Alternatives: Lanadelumab
3. Prophylaxis prior to surgery
 EACA (E Amino Caproic Acid)
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29
Q

Serotonin receptors

A

5HT1-5HT7

All are GPCR except 5HT3 (which is a ion channel)

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30
Q

5HT1 receptors

A 
5HT1:
 Gi coupled
 Presynaptic on location
Two types:
1. 5HT1A:
 Location serotonergic neurons
2. 5HT1B/1D:
 Location 5th cranial nerve
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31
Q

5HT1 agonists

A
  1. Buspirone
  2. Ipsapirone
  3. Gepirone
    Anxiolytics as they reduce serotonin release
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32
Q

Pathology of migraine

A

The CGRP neurotransmitter released by trigeminal nerve causes vasodilation of meningeal blood vessel via CHRPR.
Excess activation of the nerve ➡️ increased vasodilation ➡️ migraine

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33
Q

Treatment of migraine

A
  1. 5HT1B/1D agonist like triptans
  2. Ergot alkaloids like dihydroergotamine
  3. NSAIDs in mild attack
  4. Opioids like pethidine
  5. D2 blockers in acute type like chlorpromazine
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34
Q

5HT1B/1D agonist uses

A

Of Frovatriptan and Navatriptan:
1. More preferred for a prolonged attack of migraine
2. Treatment of migraine precipitated by menstruation
Of Rizatriptan and Eletriptan:
Best for acute attack of migraine

35
Q

5HT1B/1D agonists

Examples

A
  1. Sumatriptan:
    Least oral bioavailability, PPB, BBB penetration, efficacy, but safest in pregnancy
  2. Frovatriptan-longest acting
  3. Navatriptan
    Last 2 have slow absorption and onset ➡️ long acting
  4. Rizatriptan-faster and maximum efficacy
  5. Eletriptan
    Last 2 have fast absorption and onset
36
Q

New drugs for prophylaxis of migraine

A 
CGRP blockers:
1. Fremanexumab
2. Glacanezumab
CGRPR blocker: Erenumab
Calcitonin gene related peptide
37
Q

5HT1B/1D agonists CI and side effects

A 
1. Causes vasoconstriction so CI in:
• Ischaemic heart disease
• Stroke/ TIA
• Peripheral vascular disease
2. Arrhythmia
3. Pain in jaw, sweating
38
Q

Ergotamine

A 
Stimulates:
1. 5HT1B/1D - CGRP
2. 5HT2 - VC
3. α1 - VC
Can cause gangrene of organs with end arteries. Eg., fingers
Then DoC is:
1. Nitroprusside
2. Nitroglycerin
39
Q

Dihydroergotamine

A 
Stimulates:
1. 5HT1B/1D - CGRP
2. 5HT2 - VC
3. α1 - VC 
Less potent vasoconstrictor compared as ergotamine
Well tolerated
40
Q

Opioids against migraines

A

Butorphanol (Intranasal)
Pethidine (intramuscular)
Used only in case of drug resistant attacks

41
Q

D2 blockers against migraines

A

Chlorpromazine
Metoclopramide
Decreases dopamine effect

42
Q

Drugs used in migraine prophylaxis

A 
Flunarazine. 
Can. Cyprohepadine, Candesartan, clonidine
P. Propranolol (DoC), pizotifen, phenelzine
R. } increases GABA like
E. } Gabapentin
V. Valproate 
E. 
N. Nortriptyline
T. Topiramate
Migraine.  Methysergide
43
Q

5HT2 antagonists examples

A
  1. Cyprohepadine: migraine prophylaxis
  2. Methysergide: migraine prophylaxis
  3. Ketanserin: HTN
  4. Flibanserin: HSDD
44
Q

Cyprohepadine

A 
5HT2 antagonists 
Uses:
1. Prophylaxis of migraine
2. Cold urticaria
3. Serotonin syndrome
4. Carcinoid syndrome
5. Weight gain in cancer patients
45
Q

Methysergide

A 
5HT2 antagonist
Uses:
1. Prophylaxis of migraine
But it can cause fibrosis:
1. Pulmonary
2. Cardiac
3. Retro peritoneal
46
Q

Ketanserin

A

5HT2 and α1 blocker
Uses:
1. Treatment of HTN
2. Treatment of erectile dysfunction

47
Q

Flibanserin

A

5HT2 blocker and 5HT1 agonist
Uses:
1. Treatment of HSDD

48
Q

5HT2 receptor agonist

A

Locaserin
Anorexic agent
Treatment of obesity

49
Q

Treatment of obesity

A
  1. Anorexic agents
  2. Lipase inhibitor
  3. Lipolysis stimulator
  4. Unknown mechanisms
50
Q

Anorexic drugs used for treatment of obesity

A
  1. Locaserin
  2. Liraglutide
  3. Phentermine
51
Q

Lipase inhibitors and lipolysis stimulants that are used for treatment of obesity

A

Lipase inhibitors: Orlistat

Lipolysis stimulants: Mirabegron (β3 agonist)

52
Q

Drugs with unknown mechanisms that are used for treatment of obesity

A
  1. Topiramate
  2. Naltrexone
  3. Bupropion
53
Q

Banned drugs for obesity

A
  1. Rimonabant: suicidal tendency
  2. Sibutramine: MI
  3. Phenylpropanolamine: stroke
54
Q

General uses of 5HT3 inhibitors and 5HT4 stimulants

A

5HT3 inhibitors: anti emetic
5HT4 stimulants: prokinetic
Involved in GIT

55
Q

Synthesis of eicosanoids

A 
Arachidonic acid is acted on by COX-1 and 2 and 5-LOX
1. COX-1 and 2:
 PG: pain, inflammation and pyrexia
 TX-A2: aggregant, vasoconstriction
2. 5-LOX:
 Leukotrienes-C4,D4: bronchoconstriction
56
Q

Drugs which inhibits the leukotrienes

A 
Drugs inhibiting 5-LOX:
 Zileutron
Drugs inhibiting leukotriene-C4D4: 
 Montelukast, Zafirlukast
Used in bronchial asthma as they cause bronchodilation
57
Q

PG E analogies

A 
PG E1 analogues (patency of ductus arteriosus):
1. Misoprostol 
2. Alprostadil 
PG E2 analogue:
 Dinoprostone: cervical ripening
58
Q

Misoprostol

A 
PG-E1 analogue
Uses:
1. Maintain patency of ductus arteriosus (like alprostadil)
2. Abortion
3. Post Partum Haemorrhage
4. Gastric ulcer
59
Q

Alprostadil

A

PG-E1 analogue
Uses:
1. Maintain patency of ductus arteriosus (like misoprostol)
2. Erectile dysfunction (vasodilation)

60
Q

Dinoprostone

A 
PG E2 analogue
Uses:
1. DoC for cervical ripening
2. Post partum haemorrhage
3. Abortion
61
Q

PG I2 (thrombocyclin) increasing drugs

A 
All are used in pulmonary hypertension 
1. Analogue: Epoprosterenol
2. Synthetic PG I2:
• Iloprost
• Beraprost
• Treprostinil
3. PG I2 receptor agonist: Selexipag
62
Q

PG F2α analogues

A
  1. Carboprost:
    Used in PPH and abortion
  2. Latanaprost and Bimatoprost
    DoC for open angle glaucoma and normal tension glaucoma
63
Q

Non selective NSAIDs

A
  1. Acetaminophen: osteoarthritis
  2. Aspirin: R arthritis and niacin induced flushing
  3. Indomethacin: Gout and Bartter syndrome
  4. Ibuprofen and its 3 derivatives
  5. Piroxicam: chronic pain
  6. Ketorolac: potent analgesic
  7. Meloxicam, Etodolac and Diclofenac
64
Q

Acetaminophen or paracetamol

A

Non selective NSAID
Good analgesic and anti pyretic- in osteoarthritis
Poor anti inflammatory drug
Most common cause of drug poisoning, features:
1. Hypoglycaemic coma
2. Renal tubular necrosis
3. Hepatotoxicity

65
Q

Acetaminophen poisoning

Mechanism and microscopy

A

NAPQI-Metabolite of acetaminophen ➡️ depletes glutathione ➡️ increased free radicals ➡️ liver damage
Microscopy:
Centrilobular necrosis with periportal sparring

66
Q

Acetaminophen toxicity

Dosage and prediction

A 
Dosage for toxicity:
 >10 gm
 >150-250 mg/kg
If more than 20 gm, then fatal
Prediction is using Rumack Mathew nomogram
67
Q

Treatment of acetaminophen toxicity

A
  1. Charcoal:
    If less than 4 hours of consumption
    (Gastric lavage is not done)
  2. N-Acetyl cysteine: DoC
    Block NAPQI and it replenishes glutathione
    If no response ➡️ Fulminant liver failure (most common cause)
    Treatment: emergency liver transplantation
68
Q

Aspirin

Effects

A 
Irreversible inhibitor of COX (non selective NSAID)
At low doses:
 50-325 mg/day 
 Anti aggregant
At high doses:
 3-4 gm/day
 Anti inflammatory
69
Q

Uses of aspirin

A 
1. Analgesic of choice in:
• Rheumatoid arthritis
• Rheumatic arthritis
2. DoC: niacin induced flushing (which occurs due to increase in PGs)
3. Anti aggregant
70
Q

Aspirin toxicity

A 
Dose: >10 gm
1. Respiratory alkalosis followed by compensatory metabolic acidosis
2. Hyperthermia
3. Hypoglycaemia
4. Seizures
5. Pulmonary oedema in elderly
Treatment: urine alkalinisation
In case of pulmonary oedema, dialysis is done
71
Q

Indomethacin

A 
1. DoC for:
• acute gout 
• Bartter syndrome
2. Analgesic of choice for:
• psoriatic arthritis
• reactive arthritis
3. Closure of PDA (DoC: ibuprofen)
72
Q

Side effects of indomethacin

A

Non selective NSAID

  1. Nephrotoxicity
  2. Pancreatitis
73
Q

Ibuprofen

A

Non selective NSAID
Used as analgesic and anti inflammatory drug
DoC: closure of PDA
Side effects:
1. MCC of drug induced aseptic meningitis
2. Ocular: blurring of vision and toxic amblyopia

74
Q

Derivatives of ibuprofen

A
  1. Ketoprofen
  2. Flurbiprofen: miotic agent
  3. Nimesulide
75
Q

Ketoprofen

A

Derivative of ibuprofen (non selective NSAID)
Extra effects:
1. Stabilises lysosomes
2. Inhibits bradykinin

76
Q

Flurbiprofen

A

Derivative of ibuprofen (non selective NSAID)

Used in intraoperative miosis in ocular surgery

77
Q

Nimesulide

A 
Derivative of ibuprofen (non selective NSAID)
Use:
1. Analgesic
2. Anti inflammatory
Side effect: Hepatotoxic 
CI:
1. Children <12 years
2. Adults for more than 15 days
78
Q

Piroxicam

A 
Non selective NSAID 
Longest acting (enterohepatic circulation) with slow onset of action
Use: chronic pain
79
Q

Ketorolac

A

Non selective NSAID
Very potent analgesic (as opioids)
Post operative analgesic
Also used as eye drops (topical) as analgesic

80
Q

Side effects of non selective NSAIDs

A
  1. GIT ulcer:
    DoC- PPI
    Most specific drug: Misoprostol
  2. Nephrotoxic: renal papillary necrosis
  3. All are cardiotoxic except low dose aspirin
  4. Hypersensitivity like urticaria, rashes,…
  5. Decrease diuretic and anti hypertensive effect
    Not effective in neuropathic pain
81
Q

Selective COX-II inhibitors

A
  1. Celecoxib: least selective
  2. Lumiracoxib > Etoricoxib:
    Most selective
    Longest acting
  3. Valdecoxib: shortest acting
  4. Parecoxib:
    water soluble
    Used in post operative pain
82
Q

Side effects of selective COX-II inhibitors

A
  1. Refecoxib and Valdecoxib increases risk of MI
  2. Lumiracoxib (from diclofenac) is hepatotoxic
    These drugs are banned
83
Q

Dual 5-LOX and COX inhibitors

A
  1. Licofelone
  2. Tepoxalin
    Future anti inflammatory drugs
    Lesser GIT side effects
84
Q

NSAIDS more selective for COX-II among the non selective drugs

A
  1. Etodolac (most selective)
  2. Meloxicam
  3. Diclofenac
    Use: analgesic
    Diclofenac:
    • hepatotoxic
    • Formulated with Misoprestol to protect GIT

Pharmacology MBBS (19 decks)

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