Antihistamines Flashcards
Cetrizine
2nd generation H1 blocker- longer acting with more sedating effect than other 2nd generation blockers
Fexofenadine
2nd generation H1 blocker - lower incidence of sedation
Desloratadine
2nd generation H1 blocker
Loratadine
2nd generation H1 blocker - Long acting with little sedation
Chloropheniramine
1st generation H1 blocker - slight sedation; common component of OTC “cold” medications
diphenhydramine
1st generation H1 blocker
- used to suppress extrapyramidal, Parkinson’s-like acute dystonic reactions and sx associated with the use of antipsychotic medications
- safe cheap and effective
promethazine
1st generation H1 blocker, used as an antiemic to prevent motion sickness
azelastine hydrochloride
- 1% nasal spray used for seasonal allergic rhinitis
- second generation H1 blocker
AE’s: somnolence, bitter taste, nasal burnining, sore throat, dry mouth
1st vs. 2nd generation H1 blockers?
2nd generation drugs do not cross BBB due to it being more hydrophilic
- Thus the muscarinic receptors in the CNS are not stimulated, and there is no drowsiness as a SE
- have longer elimination t1/2 than 1st generation, thus have longer duration of action
- lower incidence of antimuscarinic side effect: i.e. dry mouth, dysuria
what are antihistamines effective for?
sneezing, nasal itching, nasal discharge (rinorrhea)
not that effective in tx of congestion (must add decongestant)
SE’s of first generation agents?
sleepiness interfere with learning decrease work productivity impair psychomotor performance increases risk of injury
**SE’s may persist morning after taking the drug
Sedation *
CNS: dizziness, tinnitus, nervousness, insomnia, fatigue, blurred vision
GI:nausea, vomiting, loss of appetite
Dry Mouth
Urinary retention (due to antimuscarinic effect)
SE’s of second generation?
primarily GI: nausea, vomiting, loss of appetite
Decongestant drugs?
alpha agonists: cause vasoconstriction, reduce edema
- available as nasal spray or oral tablets
- pseudoephedrine, phenylephrine, naphozoline, oxymetazonline, tetrahydrozoline, xylometazoline
- Effective only for relief of nasal congestion and not sneezing, itching, or discharge (often thus combined with H1-antihistamine)
Overdose AE’s:
insomnia, excitability, headache, nervousness, palpitations, tachycardia, arrhythmia, hypertension, nausea, vomiting, and urinary retention.
- Should not be used more than 3 days in order to avoid rebound congestion and rhinitis medicamentosa -> congestion will get worse
Codeine
antitussives - opioid class used for central suppression of cough reflex
Dextromethorphan
antitussives - opioid class used for central suppression of cough reflex
list of antitussives?
codeine, detromethorphan, benoxinate (local anesthetic), diphenhydramine (antihistamine)
N-acetyl-cysteine
expectorant: Facilitate secretion or decrease viscosity of mucus to facilitate clearance of mucus secretions in airways.
breaks sulfhydryl bonds in mucus proteins; makes mucus less sticky
- also can be used for tyelonol OD
Guaifenesin
expectorant: Facilitate secretion or decrease viscosity of mucus to facilitate clearance of mucus secretions in airways.
- facilitaes removal of viscous mucous
recombinant DNAse
- useful in cystic fibrosis to break up mucus plugs
chronic problems of rhinitis?
locally delivered corticosteroids... beclomethasone dipropionate budesonide flunisolide fluticasone propionate triamcinolone acetonide
ipratropium bromide
quaternary muscarinic receptor antagonist that doesn’t get into the systemic system - thus no major systemic effects
used intranasally (Roxane) to reduce secretions in the upper and lower respiratory tract in allergic rhinitis and chronic postnasal drip syndrome.
Cromolyn sodium
nasal spray - are anti-inflammatory agents that indirectly inhibit antigen-induced bronchospasm and directly inhibit the release of histamine and other autocoids from sensitized mast cells.
May suppress the activating effects of chemoattractant peptides on eosinophils, neutrophils, and monocytes.
Cromolyn compounds do not directly relax smooth muscle, therefore they are not useful for control of acute bronchospasm.
Cromolyn compounds are primarily prophylactic. When inhaled several times daily, they inhibit both the immediate and late asthmatic responses to antigenic challenge or exercise.
intranasal corticosteroids
they are hydrophobic and can easily get into the cells - these are the most effective drugs available for relief of sx of allergic rhinitis through inhibition of inflammaiton
beclomethasone dipropionate, budesonide, flunisolide, mometasone furoate, triamcinolone acetonide
- they reduce sneezing, itching, discharge, and congestion and are available in pump/spray formulations
- have very little SE’s: dryness, irritation of nasal mucosa, sore throat, epistaxis, h/a
Montelukast
“Singulair” - blocks leukotriene receptor
- Modestly beneficial for relief of sneezing, itching, discharge, and congestion
tx of allergic conjunctivitis?
main sx. is itching, may be seasonal or perennial -
treatment:
- oral antihistamines, 2nd generation
- topical eyederops with antihistamine eye drops
- Antihistamine/decongestant combinations:
pheniramine/naphazoline (Visine A)
antazoline/naphazoline (Vasocon-A): these are over the counter, but can cause rebound vasodilation with continued use
prophylaxis of type A influenza?
Amantadine - these inhibit the uncoating of viral nucleic acid and are used for tx initiated within 48 hours after initial appearance of sx
H1 receptor activation results in?
bronchoconstriction, exocrine excretion, increased capillary permeability, vasodilation, and increased intracellular Ca2+ due to IP3, DAG
what does histamine do?
- seen in allergies, anaphylaxis, inflammation
- decreases blood pressure and increase HR
- results in histamine h/a due to vasodilation
- “triple response of Lewis”
- causes constriction of bronchioles
what are antihistamines used?
- allergic conditions - i.e. rhinitis and urticaria; but ineffective against bronchial asthma
- motion sickness- 1st generation
- insomnia - 1st generation use
