2- Antihistamines Flashcards
Which H1 antagonists are very sedating?
Diphenhydramine (Benadryl, Tylenol PM)
Doxylamine
Hydroxyzine
(first generation)
What H1 antagonists are predominatly used for motion sickness?
Diphenhydramine (Benadryl)
Dimenhydrinate (Dramamine)
(first generation)
What H1 antagonist is predominatly used for its antiemetic properties?
Promethazine
(first generation, also has motion sickness properties)
Which H1 antagonists do not enter the brain well, do not have anticholinergic effects, are not useful for motion sickness, and sedation is far less common?
Fexofenadine (Allegra)
Cetirizine (Zyrtec)
(second generation)
What antihistamines should be given for a pt with liver disease or if taking multiple drugs but avoided if kidney function is poor?
Cetirizine, Levocetirizine, Acrivastine
(excreted directly by kidney, metabolism of P-450s- liver)
When should an antihistamine be given prophylactically?
Allergic rhinitis, motion sickness
Long term use of (1st gen) antihistamines can lead to tolerance of what drug effect?
Sedation
What are the SEs of 1st gen antihistamines?
Sedation (worse if combined w/ CNS depressants)
Dry mouth
Decreased seizure threshold
What are the SEs of ALL antihistamines?
GI effects
When prescribing a 1st gen antihistamine, you should be cautious of what drug interactions?
CNS depressants
When prescribing a 2nd gen antihistamine, you should be cautious of what drug interactions?
Erythromycin, ketoconazole, grapefruit juice, cimetidine
INHIBIT antihistamine metabolism
All OTC cough and cold products should NOT be used in what age group?
Under 4 yo
Pt presents with delerium, blurred vision, diaphoresis, and is very tired. What drug class were they likely prescribed?
1st gen antihistamine
Cardiac arrythmias or sinus tachycardia are signs of what drug overdose?
2nd generation antihistamine
What drugs inhibit histamine release and are often used by direct application to nasal tissue or bronchi?
Cromolyn
Azelastine (also blocks receptors)
Cetirizine
