2 - Antihistamines Flashcards
1
Q
Histamine is synthesised and stored by human cutaneous mast cells
A
True
2
Q
Mast cells synthesise histamine from histidine via the enzyme histidine decarboxylase
A
True
3
Q
Histamine is bound to granules composed of glycosaminoglycans
A
True
4
Q
Released histamine undergoes rapid local degradation
A
True
5
Q
Cutaneous mast cells express IgE receptor on the cell surface
A
True
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
7
Q
Histamine H1 receptor is expressed in human skin
A
True
8
Q
Histamine H2 receptor is expressed in human skin
A
True
9
Q
H1 receptors mediate histamine-induced itching and the axon reflex flare
A
True
10
Q
H2 receptors have no role in histamine-evoked itching
A
True
11
Q
H2 receptors regulate T-lymphocyte activity
A
True
12
Q
Both H1 and H2 receptors participate in histamine-evoked vasodilation and increased vascular permeability
A
True
13
Q
H1 and H2 antihistamines are inverse agonists
A
True
14
Q
H1 and H2 antihistamines are inverse agonists and downregulate the constitutive activated state of the corresponding receptor
A
True
15
Q
Regular H1 antihistamine maximises the therapeutic response
A
True (inverse agonist mode of action)
16
Q
H1 antihistamines substantially relieves itching related to chronic urticaria but not the complete suppression of redness and wheals
A
True
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)
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)
19
Q
First generation antihistamines are ethers based on the imidazole ring structure of histamine
A
True
20
Q
Cimetidine and ranitidine are both H2 antihistamines
A
True
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)
22
Q
H2 antihistamines I.e. Cimetidine, ranitidine have less adverse effects than H1 antihistamines I.e. Hydroxyzine, Promethazine (sedating)
A
True
23
Q
Itching is unresponsive to H2 antihistamines
A
True
24
Q
The clinical value of the first generation H1 antihistamines is significantly limited by their adverse effects and atropine-like complications
A
True
25
First generation H1 antihistamines can cause impaired cognitive function
True
26
First generation H1 antihistamines can cause sedation
True
27
First generation H1 antihistamines can cause weight gain
True
28
First generation H1 antihistamines can cause dry mouth (atropine-like effect due to anticholinergic blockade)
True
29
First generation H1 antihistamines can cause blurred vision (atropine-like effect due to anticholinergic blockade)
True
30
First generation H1 antihistamines can cause constipation (atropine-like effect due to anticholinergic blockade)
True
31
First generation H1 antihistamines can cause urinary retention (atropine-like effect due to anticholinergic blockade)
True
32
First generation H1 antihistamines are sedating
True
33
Second generation H1 antihistamines are less sedating
True
34
Second generation H1 antihistamines have a negligible propensity to induce drowsiness and other troublesome effects of the first generation H1 antihistamines
True
35
The sedative action of the the first generation H1 antihistamines is due to the function of histamine as a neurotransmitter
True
36
H1 receptors are highly expressed in the cerebral cortex
True
37
The second generation H1 antihistamines have a low capacity to cross the blood brain barrier due to minimal lipophilicity
True (hence reduce sedation and cognitive impairment effect)
38
The first generation H1 antihistamines are more lipophilic than the second generation H1 antihistamines
True (hence first generation H1antihistamines can cross the blood brain barrier and affect the cerebral cortex)
39
The first generation H1 antihistamines have anticholinergic effects
True (first generation H1 antihistamines have anticholinergic effects of dry mouth, blurred vision, constipation, urinary retention)
40
The second generation H1 antihistamines have little or no affinity for muscarinic cholinergic receptors
True (therefore no anticholinergic effects, unlike first generation H1 antihistamines)
41
Ethanolamine, Piperidine, Phenothiazine, Alkylamine and Piperazine are 5 classes of first generation H1 antihistamines (all sedating)
True
42
Diphenhydramine is a first generation H1 antihistamine from the Ethanolamine class (sedating)
True
43
Cyproheptadine is a first generation H1 antihistamine from the Piperadine class (sedating)
True
44
Promethazine is a first generation H1 antihistamine from the Phenothiazine class (sedating)
True
45
Chlorpheniramine is a first generation H1 antihistamine from the Alkylamine class (sedating)
True
46
Hydroxyzine is a first generation H1 antihistamine from the Piperazine class (sedating)
True
47
H1 antihistamines does not bind to H2 and H3 receptors
True
48
First generation H1 antihistamines are lipophilic
True
49
First generation H1 antihistamines are substantially protein bound
True
50
First generation H1 antihistamines are metabolised via the CYP 450 system in the liver
True
51
The plasma half life of first generation H1 antihistamines may be greatly prolonged in patients with liver disease
True (due to metabolism of the antihistamine via the CYP 450 system in the liver)
52
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
True (due to metabolism of the antihistamine via the CYP 450 system in the liver)
53
Evidence of suppression of the wheal and flare by antihistamines manifests 1-2 hours after oral administration
True (oral antihistamine administered during or after the onset of an allergic response may be less effective than expected)
54
Evidence of maximum suppression of the wheal and flare by antihistamines occurs later than a time to achieve a maximum plasma level
True (oral antihistamine administered during or after the onset of an allergic response may be less effective than expected)
55
Antihistamines should be given as a preventative rather than on a PRN basis
True
56
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
True
57
H1 antihistamines are most effective in clinical situations if used prophylactically
True
58
The half life of H1 antihistamines in skin exceeds their plasma half life
True
59
Closed angle glaucoma is a contraindication to use of first generation H1 antihistamines
True (contraindicated due to anticholinergic effect)
60
First generation H1 antihistamines undergoes metabolism in the liver and then are excreted in the urine
True
61
Metabolism of first generation H1 antihistamines is via the CYP 450 system
True
62
Cetirizine (second generation H1 antihistamine) is the active metabolite of Hydroxyzine (first generation H1 antihistamine)
True
63
Cyproheptadine (Piperadine class of first generation H1 antihistamines) claims to have anti-serotonin properties as well
True
64
Second generation H1 antihistamines have a high therapeutic index (ratio of minimum toxic dose and minimum therapeutic dose)
True (led to advocacy of off label usage in doses in excess of the licensed dosage)
65
Second generation H1 antihistamines are poorly lipophilic and do not readily cross the blood brain barrier
True
66
Second generation H1 antihistamines have little or no anticholinergic activity
True
67
Fexofenadine, Loratadine, Desloratadine, Cetirizne and Levocetirizine are 5 second generation H1 antihistamines
True
68
Cardiotoxicity is not a recognised side effect of currently available second generation H1 antihistamines
True
69
There is limited published evidence of the efficacy and safety of prescribing doses of second generation H1 antihistamines in excess of the licensed dosage
True
70
Many second generation H1 antihistamines either derive from a prodrug or are in the form of an active metabolite
True
71
Fexofenadine (long acting second generation H1 antihistamine) is the active drug derived from the prodrug terfenadine via CYP3A4 metabolism in the liver
True
72
Cetirizine (second generation H1 antihistamine) is 1 of the 2 active metabolites derived from Hydroxyzine
True (Levocetirizine is the other active metabolite from Hydroxyzine)
73
Levocetirizine (second generation H1 antihistamine) is 1 of the 2 active metabolites derived from Hydroxyzine
True (Cetirizine is the other active metabolite from Hydroxyzine)
74
Desloratadine (second generation H1 antihistamine) is the active metabolite of Loratadine (also a second generation H1 antihistamine)
True
75
Fexofenadine (long acting second generation H1 antihistamine) is excreted unchanged (not metabolised in the liver) largely in the faeces but also in the urine
True
76
Fexofenadine (long acting second generation H1 antihistamine) does not cause tolerance after repeated administration
True
77
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
True
78
There is no evidence that Fexofenadine (long acting second generation H1 antihistamine) is converted back to its prodrug terfenadine
True (no evidence of back metabolism)
79
There is no need for dosage adjustment of fexofenadine (long acting second generation H1 antihistamine) in the elderly or renal/hepatic impairment
True
80
There is no evidence of Cardiotoxicity with fexofenadine (long acting second generation H1 antihistamine)
True
81
Loratadine is a long acting second generation H1 antihistamine
True
82
Tolerance to repeated doses of Loratadine (long acting second generation H1 antihistamine) is not an issue
True
83
A lower dosage of Loratadine (long acting second generation H1 antihistamine) is recommended for patient with chronic renal or hepatic disease
True (although renal and hepatic impairment appear to have no major influence on the drug's pharmacokinetics)
84
Loratadine is rapidly transformed to Desloratadine (active metabolite)
True
85
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)
True
86
Loratadine (long acting second generation H1 antihistamine) has some effect on the function of the myocardial K+ channels, but does not cause cardiac dysrhythmias
True
87
Desloratadine (second generation H1 antihistamine and active metabolite of Loratadine) is more potent than Loratadine in suppressing the histamine wheal
True
88
Both Loratadine and its active metabolite Desloratadine (both second generation H1 antihistamines) have negligible/minimal urinary excretion
True
89
Desloratadine is not metabolised via the CYP P450 enzyme pathway
True (not metabolised by the liver and therefore can be safely administered with macrolides and imidazoles/triazoles antifungals which are CYP 450 inhibitors)
90
Cetirizine (second generation H1 antihistamine) is primarily excreted unchanged in the urine
True
91
Cetirizine (second generation H1 antihistamine) causes significant histamine wheal suppression in 20-60 mins and lasts for 24 hours
True
92
Cetirizine (second generation H1 antihistamine) may cause drowsiness especially if off label dosages are prescribed
True
93
Plasma levels of cetirizine (second generation H1 antihistamine) are higher in patients with chronic renal or liver disease
True (reduced dosage recommended)
94
Cetirizine is considered the most sedating second generation H1 antihistamine
True
95
Drugs that increase the serum levels of antihistamines may pose a major cardiovascular risk
True
96
Macrolides antibiotics (erythromycin, clarithromycin) are CYP3A4 inhibitors and may increase the risk for torsades de pointes with Loratadine
True
97
Azole antifungal agents (ketoconazole, itraconazole, fluconazole) are CYP3A4 inhibitors and may increase the risk for torsades de pointes with Loratadine
True
98
HIV-1 protease inhibitors (ritonavir, indinavir) are CYP3A4 inhibitors and may increase the risk for torsades de pointes with Loratadine
True
99
SSRI antidepressants may increase the risk for torsades de pointes with Loratadine
True
100
Grapefruit juice is a CYP3A4 inhibitors and may increase the risk for torsades de pointes with Loratadine
True
101
Cimetidine (H2 antihistamine) is a CYP3A4 inhibitor and may increase Loratadine levels
True
102
Alcohol and other CNS depressants may produce an additive sedating effect when used in combination with first generation H1 antihistamines
True
103
Monoamine oxidase inhibitors may prolong or intensify the sedating and anticholinergic effects especially with first generation H1 antihistamines
True
104
H1 antihistamines have not been associated with documented increased Fetal risk in pregnancy
True
105
The first generation H1 antihistamines Chlorpheniramine and Diphenhydramine have a relatively long track record of safety in pregnancy
True
106
In regard to the second generation H1 antihistamines, Data are inadequate to draw conclusions on safety in pregnancy
True
107
Tachyphylaxis/tolerance to antihistamines may be due to poor compliance due to adverse effects
True
108
Doxepin is a TCA drug with potent H1 and H2 antihistamine activity
True
109
Doxepin (TCA drug with H1 and H2 antihistamine activity) should not be administered topically or systemically concurrently with other antidepressants
True
110
Topical Doxepin may cause allergic contact dermatitis (dermatitis medicamentosa)
True
111
Doxepin (TCA drug with H1 and H2 antihistamine activity) should not be administered in the presence of severe heart disease
True
112
Doxepin (TCA drug with H1 and H2 antihistamine activity) should not be abruptly withdrawn
True
113
Menthol 1% cream may be useful in chronic urticaria
True
