Pharmacology Flashcards
Cholinergic innervation of respiratory tract
Provide predominant neuronal tone to respiratory tract
Activation of muscarinic receptors by acetylcholine produces bronchoconstriction of smooth muscle, increases in respiratory glandular secretions, and dilation of blood vessels
Role of B-2 receptors in respiratory tract
Primarily found on bronchial smooth muscle
Stimulation of B2-adrenergic receptors on bronchial smooth muscle causes bronchodilation
Role of alpha-1 receptors in respiratory tract
Primarily found on respiratory vascular smooth muscle
Stimulation causes vasoconstriction
Role of leukotriene receptors in respiratory tract
Stimulation of leukotriene receptors on bronchial smooth muscle causes bronchoconstriction
Role of histamine receptors in respiratory tract
Stimulation of Histamine H1 receptors in bronchial smooth muscle causes bronchoconstriction
Stimulation of H1 receptors on bronchial vasculature causes vasodilation
Pharmacodynamics of first generation H1 blockers
Primarily block H1 channels
Secondary effect in blocking cholinergic and alpha adrenergic receptors
Effects of alpha-adrenergic channel blockade
Hypotension
Dizziness
Reflex Tachycardia
CNS sedation
Effects of cholinergic blockade
Dry mouth
Urinary retention
Sinus tachycardia
Which first generation H1 blocker also blocks a-adrenergic receptors?
Promethazine
Which 1st generation H1 blockers (2) also block cholinergic receptors?
Diphenhydramine
Promethazine
First generation antihistamines (4)
Diphenhydramine
Promethazine
Chlorpheniramine
Meclizine
2nd generation anti-histamines (3)
Fexofenadine
Loratadine
Cetirizine
Pharmacokinetics of first generation anti-histamines
Rapid oral absorption
Penetrate rapidly into CNS
Metabolized by liver
Shorter duration of action (4-8 hrs)
Pharmacokinetics of second generation anti-histamines
Rapid oral absorption
Less penetration into CNS
Metabolized by liver
Longer duration of action (12-24 hour dosing)
Clinical uses of anti-histamines
Allergic reactions (H1 receptor block)
Cough suppression (Na+ channel block)
Side effects of anti-histamines
Sedation
Dry mouth (anti-cholinergic)
Hypotension (anti-alpha adrenergic)
Topical decongestants (3)
Phenylephrine
Oxymetazoline
Xylometazoline
Decongestant (sympathomimetic) mechanism
Stimulate alpha-1 adrenergic receptors on vascular smooth muscle, resulting in vasoconstriction of vessels dilated by histamine or inflammatory response; promotes drainage and decreases congestion
Decongestants side effects - topical vs. oral
Rebound congestion (associated with topicals)
Vasoconstriction in other vascular beds can cause headaches, dizziness, nausea, hypertension (orals only)
Oral decongestant agents (2)
Pseudoephedrine - safest & most effective
Phenylephrine
Antitussives - endogenous opiate agonists (3) and mechanism
Codeine
Hydrocodone
Dextromethorphan
Act on endogenous opioid receptors to depress central cough center in brain stem
Dextromethorphan
OTC opiate agonist - does not produce respiratory depression or tolerance
Most commonly used OTC cough suppressant
Guaifenesin - Mechanism
OTC expectorant
Stimulates respiratory tract secretions, decreasing viscosity of mucus and improving mucociliary mechanism of airway clearance
Likely not more effective than fluids, cool mist, or steam
N-acetyl cysteine - Mechanism
Mucolytic agent
Splits disfulfide bridges between mucoproteins, resulting in decreased viscosity of mucus secretions
Administered via inhalation
