E3: Antihistamines CC Flashcards
What is the MOA of antihistamines?
Block action of histamine at RECEPTOR sites
What are 3 effects of histamine release?
- Vasodilation
- Increased capillary permeability
- Increased GI and pulmonary secretions
List 7 clinical uses of antihistamine drugs.
- Allergic conditions (rhinitis, dermatitis, allergic conjunctivitis)
- Hypersensitivity rxn to drugs
- Anaphylaxis
- Urticaria
- Motion sickness
- Vertigo
- Insomnia
List the 6 ORAL 1st gen H1-blockers.
- Diphenhydramine (Benadryl)
- Chlorpheniramine
- Dimenhydrinate (Dramamine)
- Promethazine (Phenergan)
- Meclizine
- Hydroxyzine
List the 3 ORAL 2nd gen H1-blockers.
- Loratadine (Claritin)
- Certirizine (Zyrtec)
- Fexofenadine (Allegra)
What is the name of the nasal spray antihistamine?
Azelastine (+/- Fluticasone)
List the 4 EYE DROP antihistamines.
- Azelastine
- Ketotifen
- Naphazoline
- Olopatadine
Antihistamines are _______ drugs. List the side effects associated with this.
ANTICHOLINERGIC
- Red as a beet
- Dry as a bone
- Blind as a bat (midriasis)
- Mad as a hatter
- Hot as a hare
What are 2 approved antihistamines for pilots (likely similar to other patients working in transport/operating machinery). What is the protocol for starting these medications? How does this differ for non-approved allergy meds?
Approved use:
- Loratadine (Claritin)
- Fexofenadine (Allegra)
- May be used only AFTER adequate trial without side effects
Non-approved anti-histamines:
-Pilot must ground themselves for 5x the drug half life
What medications should not be used/discontinued in a male patient with BPH + allergies? What would you recommend as first line?
- Avoid decongestants and 1st gen anti-histamines like Benadryl/Sudafed (can cause urinary retention)
- Nasal steroids are first line
What medications should be avoided/discontinued in a pt with glaucoma (especially closed-angle) + allergies? What would be the recommended tx?
- Avoid decongestants, antihistamines, AND steroids (including nasal)
- Consult pt’s optho doc; consider immunotherapy
Describe the clinical presentation of Scabies. What can be used to treat this?
Clinical presentation: Intense itching, especially at night; Presence of burrow lesions
Tx: Permethrin Cream 5% (to soles and feet q 8-12 hours)
What is the time span for acute vs. chronic urticaria? What is chronic urticaria often associated with?
Acute: <6 weeks; usually self-limiting
Chronic: >6 weeks; often associated with an autoimmune dz
Which 2 medications can be used as ADJUNCT therapy for the tx of new onset urticaria? What class would you recommend for the tx of chronic urticaria?
Acute urticaria adjunct tx: H2 blockers (Zantac or Pepcid)
Chronic urticaria: Non-sedating (2nd gen) antihistamines
What tx can you recommend for contact dermatitis (such as poison ivy)?
- Steroid cream (avoiding high potency on face)
- 2nd gen antihistamines
- Oral steroid taper IF not improving
You have a patient with a PCN allergy who accidentally takes a PCN-based medication. They consequently develop hives. How would you tx this patient?
- Discontinue the offending medication
- 2nd gen antihistamine
- Can consider IM steroids and/or IM antihistamine
- Can also consider tapering course of oral steroids based on severity of sxs
What body systems can be affected by anaphylaxis (Ex: Rxn to immunotherapy injection)?
Affects >1 body part simultaneously
- Skin and mucosa
- Respiratory
- GI
- Cardiac (hypotension, syncope, tachycardia)
EMERGENCY! IMMEDIATE MEDICAL TX REQUIRED!
What is the DOC for the tx of anaphylaxis? What other 2 medications should also be given?
DOC: Epinephrine
Also give Benadryl + IM/IV glucocorticoid
Between 1st gen and 2nd gen antihistamines, which of the 2 are longer acting? Which crosses the BBB?
1st gen: Crosses BBB (sedation); shorter acting
2nd gen: Nonsedating; longer acting (therefore once daily dosing)
In general, what are the 4 groups of high risk patients for select antihistamines (more harm than benefit)?
- BPH
- Glaucoma
- Very young or very old
- Avoidance of pts with high risk occupations
