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Derm Pharm 2020 > 2 - Antihistamines > Flashcards

2 - Antihistamines Flashcards

1
Q

Histamine is synthesised and stored by human cutaneous mast cells

A

True

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2
Q

Mast cells synthesise histamine from histidine via the enzyme histidine decarboxylase

A

True

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3
Q

Histamine is bound to granules composed of glycosaminoglycans

A

True

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4
Q

Released histamine undergoes rapid local degradation

A

True

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5
Q

Cutaneous mast cells express IgE receptor on the cell surface

A

True

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6
Q

Cross linking of adjacent IgE receptors by antigen culminates in the release of histamine and other mediators I.e. Proteases and cytokines

A

True

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7
Q

Histamine H1 receptor is expressed in human skin

A

True

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8
Q

Histamine H2 receptor is expressed in human skin

A

True

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9
Q

H1 receptors mediate histamine-induced itching and the axon reflex flare

A

True

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10
Q

H2 receptors have no role in histamine-evoked itching

A

True

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11
Q

H2 receptors regulate T-lymphocyte activity

A

True

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12
Q

Both H1 and H2 receptors participate in histamine-evoked vasodilation and increased vascular permeability

A

True

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13
Q

H1 and H2 antihistamines are inverse agonists

A

True

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14
Q

H1 and H2 antihistamines are inverse agonists and downregulate the constitutive activated state of the corresponding receptor

A

True

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15
Q

Regular H1 antihistamine maximises the therapeutic response

A

True (inverse agonist mode of action)

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16
Q

H1 antihistamines substantially relieves itching related to chronic urticaria but not the complete suppression of redness and wheals

A

True

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17
Q

H1 antihistamines incompletely suppresses the redness of chronic urticaria

A

True (incompletely suppresses redness which suggests that other mediators besides histamine is involved in the pathology)

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18
Q

H1 antihistamines incompletely suppresses the wheals of chronic urticaria

A

True (incompletely suppresses the wheals which suggests that other mediators besides histamine is involved in the pathology)

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19
Q

First generation antihistamines are ethers based on the imidazole ring structure of histamine

A

True

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20
Q

Cimetidine and ranitidine are both H2 antihistamines

A

True

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21
Q

H2 antihistamines I.e. Cimetidine and ranitidine have not been successful either alone of in combination with H1 antihistamines in the treatment of urticaria

A

True (even though H2 antihistamines are expressed in skin blood vessels and may influence histamine-mediated vasodilation, they have been disappointing in practice for treatment of urticaria)

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22
Q

H2 antihistamines I.e. Cimetidine, ranitidine have less adverse effects than H1 antihistamines I.e. Hydroxyzine, Promethazine (sedating)

A

True

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23
Q

Itching is unresponsive to H2 antihistamines

A

True

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24
Q

The clinical value of the first generation H1 antihistamines is significantly limited by their adverse effects and atropine-like complications

A

True

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25
Q

First generation H1 antihistamines can cause impaired cognitive function

A

True

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26
Q

First generation H1 antihistamines can cause sedation

A

True

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27
Q

First generation H1 antihistamines can cause weight gain

A

True

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28
Q

First generation H1 antihistamines can cause dry mouth (atropine-like effect due to anticholinergic blockade)

A

True

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29
Q

First generation H1 antihistamines can cause blurred vision (atropine-like effect due to anticholinergic blockade)

A

True

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30
Q

First generation H1 antihistamines can cause constipation (atropine-like effect due to anticholinergic blockade)

A

True

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31
Q

First generation H1 antihistamines can cause urinary retention (atropine-like effect due to anticholinergic blockade)

A

True

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32
Q

First generation H1 antihistamines are sedating

A

True

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33
Q

Second generation H1 antihistamines are less sedating

A

True

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34
Q

Second generation H1 antihistamines have a negligible propensity to induce drowsiness and other troublesome effects of the first generation H1 antihistamines

A

True

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35
Q

The sedative action of the the first generation H1 antihistamines is due to the function of histamine as a neurotransmitter

A

True

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36
Q

H1 receptors are highly expressed in the cerebral cortex

A

True

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37
Q

The second generation H1 antihistamines have a low capacity to cross the blood brain barrier due to minimal lipophilicity

A

True (hence reduce sedation and cognitive impairment effect)

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38
Q

The first generation H1 antihistamines are more lipophilic than the second generation H1 antihistamines

A

True (hence first generation H1antihistamines can cross the blood brain barrier and affect the cerebral cortex)

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39
Q

The first generation H1 antihistamines have anticholinergic effects

A

True (first generation H1 antihistamines have anticholinergic effects of dry mouth, blurred vision, constipation, urinary retention)

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40
Q

The second generation H1 antihistamines have little or no affinity for muscarinic cholinergic receptors

A

True (therefore no anticholinergic effects, unlike first generation H1 antihistamines)

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41
Q

Ethanolamine, Piperidine, Phenothiazine, Alkylamine and Piperazine are 5 classes of first generation H1 antihistamines (all sedating)

A

True

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42
Q

Diphenhydramine is a first generation H1 antihistamine from the Ethanolamine class (sedating)

A

True

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43
Q

Cyproheptadine is a first generation H1 antihistamine from the Piperadine class (sedating)

A

True

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44
Q

Promethazine is a first generation H1 antihistamine from the Phenothiazine class (sedating)

A

True

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45
Q

Chlorpheniramine is a first generation H1 antihistamine from the Alkylamine class (sedating)

A

True

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46
Q

Hydroxyzine is a first generation H1 antihistamine from the Piperazine class (sedating)

47
Q

H1 antihistamines does not bind to H2 and H3 receptors

48
Q

First generation H1 antihistamines are lipophilic

49
Q

First generation H1 antihistamines are substantially protein bound

50
Q

First generation H1 antihistamines are metabolised via the CYP 450 system in the liver

51
Q

The plasma half life of first generation H1 antihistamines may be greatly prolonged in patients with liver disease

A

True (due to metabolism of the antihistamine via the CYP 450 system in the liver)

52
Q

The plasma half life of first generation H1 antihistamines may be greatly prolonged if concurrently administered in patients on CYP3A4 inhibitors I.e. Erythromycin or ketoconazole

A

True (due to metabolism of the antihistamine via the CYP 450 system in the liver)

53
Q

Evidence of suppression of the wheal and flare by antihistamines manifests 1-2 hours after oral administration

A

True (oral antihistamine administered during or after the onset of an allergic response may be less effective than expected)

54
Q

Evidence of maximum suppression of the wheal and flare by antihistamines occurs later than a time to achieve a maximum plasma level

A

True (oral antihistamine administered during or after the onset of an allergic response may be less effective than expected)

55
Q

Antihistamines should be given as a preventative rather than on a PRN basis

56
Q

The therapeutic half life of antihistamines in the skin is frequently considerably in excess of the plasma half life because of the persistence of the antihistamines at tissue sites

57
Q

H1 antihistamines are most effective in clinical situations if used prophylactically

58
Q

The half life of H1 antihistamines in skin exceeds their plasma half life

59
Q

Closed angle glaucoma is a contraindication to use of first generation H1 antihistamines

A

True (contraindicated due to anticholinergic effect)

60
Q

First generation H1 antihistamines undergoes metabolism in the liver and then are excreted in the urine

61
Q

Metabolism of first generation H1 antihistamines is via the CYP 450 system

62
Q

Cetirizine (second generation H1 antihistamine) is the active metabolite of Hydroxyzine (first generation H1 antihistamine)

63
Q

Cyproheptadine (Piperadine class of first generation H1 antihistamines) claims to have anti-serotonin properties as well

64
Q

Second generation H1 antihistamines have a high therapeutic index (ratio of minimum toxic dose and minimum therapeutic dose)

A

True (led to advocacy of off label usage in doses in excess of the licensed dosage)

65
Q

Second generation H1 antihistamines are poorly lipophilic and do not readily cross the blood brain barrier

66
Q

Second generation H1 antihistamines have little or no anticholinergic activity

67
Q

Fexofenadine, Loratadine, Desloratadine, Cetirizne and Levocetirizine are 5 second generation H1 antihistamines

68
Q

Cardiotoxicity is not a recognised side effect of currently available second generation H1 antihistamines

69
Q

There is limited published evidence of the efficacy and safety of prescribing doses of second generation H1 antihistamines in excess of the licensed dosage

70
Q

Many second generation H1 antihistamines either derive from a prodrug or are in the form of an active metabolite

71
Q

Fexofenadine (long acting second generation H1 antihistamine) is the active drug derived from the prodrug terfenadine via CYP3A4 metabolism in the liver

72
Q

Cetirizine (second generation H1 antihistamine) is 1 of the 2 active metabolites derived from Hydroxyzine

A

True (Levocetirizine is the other active metabolite from Hydroxyzine)

73
Q

Levocetirizine (second generation H1 antihistamine) is 1 of the 2 active metabolites derived from Hydroxyzine

A

True (Cetirizine is the other active metabolite from Hydroxyzine)

74
Q

Desloratadine (second generation H1 antihistamine) is the active metabolite of Loratadine (also a second generation H1 antihistamine)

75
Q

Fexofenadine (long acting second generation H1 antihistamine) is excreted unchanged (not metabolised in the liver) largely in the faeces but also in the urine

76
Q

Fexofenadine (long acting second generation H1 antihistamine) does not cause tolerance after repeated administration

77
Q

Fexofenadine is a long acting second generation H1 antihistamine which inhibits the wheal and flare response lasting up to 12 hours and an elimination half life of 11-15 hours

78
Q

There is no evidence that Fexofenadine (long acting second generation H1 antihistamine) is converted back to its prodrug terfenadine

A

True (no evidence of back metabolism)

79
Q

There is no need for dosage adjustment of fexofenadine (long acting second generation H1 antihistamine) in the elderly or renal/hepatic impairment

80
Q

There is no evidence of Cardiotoxicity with fexofenadine (long acting second generation H1 antihistamine)

81
Q

Loratadine is a long acting second generation H1 antihistamine

82
Q

Tolerance to repeated doses of Loratadine (long acting second generation H1 antihistamine) is not an issue

83
Q

A lower dosage of Loratadine (long acting second generation H1 antihistamine) is recommended for patient with chronic renal or hepatic disease

A

True (although renal and hepatic impairment appear to have no major influence on the drug’s pharmacokinetics)

84
Q

Loratadine is rapidly transformed to Desloratadine (active metabolite)

85
Q

Loratadine (long acting second generation H1 antihistamine) appears to be free of Cardiotoxicity although it has some effect on the function of the myocardial K+ channels (but does not cause cardiac dysrhythmias)

86
Q

Loratadine (long acting second generation H1 antihistamine) has some effect on the function of the myocardial K+ channels, but does not cause cardiac dysrhythmias

87
Q

Desloratadine (second generation H1 antihistamine and active metabolite of Loratadine) is more potent than Loratadine in suppressing the histamine wheal

88
Q

Both Loratadine and its active metabolite Desloratadine (both second generation H1 antihistamines) have negligible/minimal urinary excretion

89
Q

Desloratadine is not metabolised via the CYP P450 enzyme pathway

A

True (not metabolised by the liver and therefore can be safely administered with macrolides and imidazoles/triazoles antifungals which are CYP 450 inhibitors)

90
Q

Cetirizine (second generation H1 antihistamine) is primarily excreted unchanged in the urine

91
Q

Cetirizine (second generation H1 antihistamine) causes significant histamine wheal suppression in 20-60 mins and lasts for 24 hours

92
Q

Cetirizine (second generation H1 antihistamine) may cause drowsiness especially if off label dosages are prescribed

93
Q

Plasma levels of cetirizine (second generation H1 antihistamine) are higher in patients with chronic renal or liver disease

A

True (reduced dosage recommended)

94
Q

Cetirizine is considered the most sedating second generation H1 antihistamine

95
Q

Drugs that increase the serum levels of antihistamines may pose a major cardiovascular risk

96
Q

Macrolides antibiotics (erythromycin, clarithromycin) are CYP3A4 inhibitors and may increase the risk for torsades de pointes with Loratadine

97
Q

Azole antifungal agents (ketoconazole, itraconazole, fluconazole) are CYP3A4 inhibitors and may increase the risk for torsades de pointes with Loratadine

98
Q

HIV-1 protease inhibitors (ritonavir, indinavir) are CYP3A4 inhibitors and may increase the risk for torsades de pointes with Loratadine

99
Q

SSRI antidepressants may increase the risk for torsades de pointes with Loratadine

100
Q

Grapefruit juice is a CYP3A4 inhibitors and may increase the risk for torsades de pointes with Loratadine

101
Q

Cimetidine (H2 antihistamine) is a CYP3A4 inhibitor and may increase Loratadine levels

102
Q

Alcohol and other CNS depressants may produce an additive sedating effect when used in combination with first generation H1 antihistamines

103
Q

Monoamine oxidase inhibitors may prolong or intensify the sedating and anticholinergic effects especially with first generation H1 antihistamines

104
Q

H1 antihistamines have not been associated with documented increased Fetal risk in pregnancy

105
Q

The first generation H1 antihistamines Chlorpheniramine and Diphenhydramine have a relatively long track record of safety in pregnancy

106
Q

In regard to the second generation H1 antihistamines, Data are inadequate to draw conclusions on safety in pregnancy

107
Q

Tachyphylaxis/tolerance to antihistamines may be due to poor compliance due to adverse effects

108
Q

Doxepin is a TCA drug with potent H1 and H2 antihistamine activity

109
Q

Doxepin (TCA drug with H1 and H2 antihistamine activity) should not be administered topically or systemically concurrently with other antidepressants

110
Q

Topical Doxepin may cause allergic contact dermatitis (dermatitis medicamentosa)

111
Q

Doxepin (TCA drug with H1 and H2 antihistamine activity) should not be administered in the presence of severe heart disease

112
Q

Doxepin (TCA drug with H1 and H2 antihistamine activity) should not be abruptly withdrawn

113
Q

Menthol 1% cream may be useful in chronic urticaria

Derm Pharm 2020 (47 decks)

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