Antihistamines, Antifungals, Antivirals Flashcards
Sources of Histamine:
- Mast Cells (intestinal mucosa, skin and lungs)
- Basophils (in blood bound to heparin)
- CNS in neurons (in synaptic vesicles)
Mechanism of H1 antihistamines:
Competitive blockade of H1 receptors (H1 receptor blockers)
Pharmacologic effects of H1 antihistamines:
- Absorption
- Onset
- Duration
- Metabolism
- Well absorbed orally
- Rapid onset = 15-30 minutes
- Duration = 3-6 hours
- Metabolism primarily by over (some kidney)
How do H1 antihistamines affect the CNS?
Produce depression (Sleepiness) Treat motion sickness
What is the action of H1 antihistamines on the Autonomic nervous system and Peripheral nervous system respectively?
ANS: Blocks constriction of respiratory smooth muscle
PNS: Blocks flare (wheals) and itch
3 Adverse effects of H1 antihistamines:
- Most cause sleepiness/drowsiness
- Xerostomia (dry mouth)
- Dry mucous membranes
- Older antihistamines caused ventricular arrhythmias
2 types of Antihistamines
- Ethanolamines
- diphenhydramine (Benadryl) - Alkylamines
- chlorpheniramine (Chlor-Trimeton)
Name 3 non-sedating antihistamines
Ioratadine (Claritin) - OTC
fexofenadine (Allegra) - OTC
desloratadine (Clarinex)
Mechanism of action for H2 antihistamines:
- Competitive blockage of H2 receptors (GI tract)
- Reduces intracellular concentration of cAMP
- Protein kinase that drives the H+/K+-ATPase pump is shut down
* *-Inhibits basal and nocturnal gastric acid secretion (evoked by histamine)
Pharmacologic effects of H2 Antihistamines:
- Absorption
- Metabolism
- If added to H1 blockers???
- Well absorbed orally
- Very little metabolism
- If aded to H1 blockers, blocks all cardiovascular effects of histamine
4 clinical uses of H2 Antihistamines:
- Peptic ulcer
- Hypersecretion of gastric acid
- GERD
- Zollinger-Ellison syndrome (gastrin producing tumor causing hypersecretion of stomach acid)
Name 4 H2 Antihistamines:
- cimetidine (Tagamet)
- famotidine (Pepcid)
- nizatidine (Axid)
- ranitidine (Zantac)
Adverse effects of H2 Antihistamines
- Minor
- Chronic use of these drugs is associated with headache, dizziness and fatigue
- Elderly = confusion, slurred speech, delirium and hallucinations
- Gynecomastia in males
- Impotence; 40% decrease in sperm count
What is the safest and most recommended drug in H2 Antihistamine class?
ranitidine (Zantac)
- Fewest drug interactions
Which drug of the H2 Antihistamine class has the most adverse reactions
- cimetidine (Tagamet)
- Inhibits cytochrome P450 to slow the clearance and increases the serum levels of many drugs
- increases risk for overdose reactions
What is cromolyn (Gastrocrom)?
A mast cell stabilizer
- Inhibits degranulation, preventing histamine release from IgE sensitized mast cells
What is cromolyn (Gastrocrom) used for?
Prophylaxis of allergies, exercise-induced asthma, and asthma
Describe when to use topical vs systemic anti fungal treatment
Systemic: chronic, extensive mucocutaneous candidiasis
Topical: Local candidiasis
- **May be used in conjunction with topical corticosteroids to manage inflammation
Which of the anti fungal therapies is preferred?
Topical versus systemic is preferred
How long to treat during anti fungal therapies
Treat for a minimum of 48 hours after symptoms subside
- usual treatment period is for 1-2 weeks
Re-evaluate at 14 days after therapy
4 topical antifungal agents
- Liquids
- Troches
- Pastilles
- Powders
nystatin (Mycostatin) mechanism of actions
Binds to sterols in fungal cell membrane, changing cell wall permeability allowing for leakage of cellular contents
-Topical
nystatin comes in what forms?
- pastilles/troches = 4-5 troches/day for 14 days
- oral suspension = 1 tsp 4-5 times/day; rinse and hold in mouth for 2 minutes; do not eat/drink afterwards for 30 minutes; soak dentures
- ointment/cream = 4-5 times per day; may be applied to dentures prior to insertion
- powder = sprinkle over dentures prior to insertion 4-5 times per day
When is clotrimazole (Mycelex) used?
when nystatin is not effective
- Not for systemic fungal infections. Topical use only
Describe dosages of different forms of clotrimazole (Mycelex)
- Troche - dissolve 1 troche 5 times/day for 14 days
- Cream - apply twice daily
- Solution - rinse twice daily
What is the adverse effect of clotrimazole
abnormal liver function
Name the two topical antifungals
- nystatin (Mycostatin)
2. clotrimazole (Mycelex)
Name the systemic antifungals
Azole antifungals
- itraconazole (Sporanox)
- fluconazole (Diflucan)
Why do you avoid systemic anti fungal drugs
- Promotes resistance of fungal organisms
- Many dangerous drug interactions
- Hepatotoxic
- itraconazole = severe cardiovascular side effects; neuropathy
T or F, Reserve systemic antifungal agents for severe cases
True
Name the parenteral anti fungal drug
amphotericin
How is amphotericin given?
by IV
amphotericin is the most effective drug for what?
against deep-seated mycotic infections
- used for fungal infections associated with HIV
Treatment for viral infections includes combination therapy of?
Antiviral drug
Topical anesthetics
Fluids, vitamins/minerals, rest
Vesicular viral lesion =
Contagious
Viral vesicle breaks =
Open lesion with draining fluid = contagious
How long do viral lesions last?
10 days
Are antibiotics effective for viral infections? Is anything else contraindicated?
No, they are ineffective
- Systemic corticosteroids are contraindicated for use during viral illnesses
Mechanism of Acyclovir (Zovirax)
Inhibits viral DNA polymerase preferentially, inhibiting viral replication
How is Acyclovir administered?
Systemically and topically
Systemic: recurrent mucosal and cutaneous herpes simplex infections
Topical: herpes labialis, mucocutaneous infections
Dosage forms of acyclovir
oral
cream/ointment
suspension
injection
2 different prescription examples for Herpes Simplex (primary infection)
- Zovirax 200 mg capsules
Disp: 50 capsules
Sig: Take 1 capsule 5 times/day for 10 days - Zovirax 200 mg capsules
Disp: 60 capsules
Sign: Take 2 capsules 3 times/day for 10 days
What is Xerese
Acyclovir 5% and hydrocoritsone 1%
External use only: lips and face
What is Penciclovir (Denver)?
For Herpes labialis: apply only to lips and face
Effect not established in immunocompromised patients
What is Famciclovir (Famvir) used for?
In immunocompetent patients
Primary use for Valacyclovir (Valtrex)
genital herpes suppression therapy
Side Effects of all antiviral drugs taken systemically
Bone marrow suppression Blood dispraises -Thrombocytopenia - Leukopenia - Aplastic anemia
