OTC Allergy and Insomnia Flashcards
what do allergies include? (5)
hay fever, food allergies, atopic dermatitis, allergic asthma, anaphylaxis
what are the symptoms of allergies?
red eyes, itchy rash, sneezing, runny nose, shortness of breath or swelling
what immunoglobin does allergies include?
IgE antibodies
what are IgE antibodies produced by and why?
B cells; in response to an allergen/antigen
what do IgE antibodies bind to?
receptors on mast cells or basophils (next exposure releases histamine)
what kind of receptors are histamine receptors?
GPCRs (q - phospholipase C)
what histamine receptor plays a predominant role in allergy response?
H1 (acute immune response)
where are H1 receptors? (4)
smooth muscles, vascular endothelial cells, heart, CNS
what does activation of the H1 receptor cause? (5)
incr vascular permeability, vasodilation, cough, smooth muscle contraction of bronchi, eosinophil chemotaxis
where are histamine receptors concentrated in the brain?
regions controlling waking/arousal: thalamus, cortex, noradrenergic, serotonergic, dopaminergic nuclei)
histamine is an important NT in the….
wake-promoting system
what is diphenhydramine?
inverse agonist at H1 receptor (blocks activity)
what does diphenhydramine do? (2)
blocks effects of histamine in blood vessels and smooth muscle cells to decr allergic rxn symptoms, suppresses medullary cough center
what are first generation antihistamines?
first developed drugs for allergies
how does diphenhydramine cause drowsiness?
crosses BBB and inversely agonizes CNS H1 receptors
what is diphenhydramine marketed as? (3)
Benadryl (OTC allergy drug), Nytol (OTC sleep aid), Tylenol Cold and Flu (OTC Cough and Cold)
what is the effect first gen antihistamines being non-selective?
cause off-target side effects
what is an antagonists/inverse agonists affinity described by?
inhibitory constant (Ki)
what is Ki?
[drug] that displaces 50% of labelled ligand (low Ki = high aff)
what off-target receptors can first gen antihistamines bind to (not H1)?
muscarinic cholinergic receptors
what are the off-target anticholinergic effects of antihistamines?
dry mouth, constipation and confusion (not recommended for older individuals)
what are 3 cons of diphenhydramine?
tolerance develops rapidly to sedative effects, decr sleep quality, long-term association w/ Alzheimers (anticholinergic effects)
what is different btwn first and second gen antihistamines? (3)
more selective for H1 receptors, poor BBB permeability (lack sedative effects), longer duration of action (decr doses)
what is cetirizine?
H1 receptor antagonist
what is the duration of action of cetirizine?
24 hrs (diphenhydramine: 4-6 hrs)
what is loratidine?
H1 inverse agonist
what is the issue with loratadine?
almost entirely bound to plasma proteins (not active)
what occurs when loratidine is given orally?
rapid first pass metabolism converts it to desloratadine (loratadine: prodrug)
what does desloratadine do?
has anti-histamine effects (poor penetration of BBB, weakly sedating)
what is the difference btwn loratadine and desloratadine half-life?
incr half-life (8 vs 27 hrs)
