Other Systemic Medications Flashcards
What are the primary histamine receptors involved in cutaneous itch?
H1, not H2
What is a disease for which histamine levels are clearly elevated?
Urticaria and angioedema (some forms). This is in contrast to atopic dermatitis where histamine levels likely are not a large contributor
Though H1 receptor antagonists are primarily used in dermatology for what disease can H2 blockers be added?
In chronic urticaria a H2 receptor blocker can be considered, but there is poor evidence for this
Which antihistamines are most often used during pregnancy?
Usually diphenhydramine or chlorpheniramine due to long safety record
What is the primary difference seen between the first and second-generation antihistamines and why is this seen?
Second-generation antihistamines are less sedating because they are less lipophilic and have decreased ability to cross the blood-brain barrier.
Main adverse effects of first-generation H1 antihistamines?
Sedation, impaired cognitive function and anticholinergic effects (dry mouth, constipation, dysuria, blurred vision) [use caution with these medications in men with enlarged prostate and dysuria. Likewise, avoid in elderly patients]
What are some important side effects of cyproheptadine?
Interferes with hypothalamic function and increases appetite, can also slow/inhibit growth in children
What are the first-generation H1 antihistamines metabolized by?
P450 system
Side effects of second-generation H1 antihistamines?
Less sedating, anticholinergic effects much less common (but caution must still be used in high-risk patients).
What is the most sedating of the second-generation antihistamines?
Cetirizine, 10% get drowsiness
What should be done in patients with hepatic or renal diseases taking second-generation antihistamines?
Loratidine, Cetirizine and derivatives should be dose reduced
fexofenadine is not metabolized by the liver and is largely excreted as is
What is the strongest of the oral antihistamines that we typically use in dermatology?
Doxepin. This tricyclic antidepressant has both H1 and H2 properties and is a much stronger antagonist of these than typical antihistamines
What is a potential side effect of topical doxepin?
Can cause allergic contact dermatitis and drowsiness
Some important side effects and contraindications for doxepin?
Do not give with other antidepressants, don’t give in those with severe heart disease, can decrease the seizure threshold, may induce manic episodes in patients with manic-depressive disorder
What is the mechanism of hydroxyurea?
Impairs DNA synthesis through inhibition of ribonucleotide diphosphate reductase; hypomethylates DNA resulting in altered gene expression
What are the dermatologic uses for hydroxyurea?
off label treatment of recalcitrant psoriasis, Sweet’s syndrome, erythromelalgia, and hypereosinophilic syndrome
What is the most common side effect of hydroxyurea?
Megaloblastic anemia (myelosuppressive)
What skin eruptions can hydroxyurea cause?
Dermatomyositis-like eruption, lichenoid drug eruption resembling graft-versus-host disease, leg ulcers, alopecia, photosensitivity, radiation recall, and hyperpigmentation of the skin and nails.
What is the mechanism of cyclophosphamide?
An alkylating agent (directly damages DNA via cross-linking).
- Nitrogen mustard derivative
- Aldophophamide is one of the metabolites and is cleaved intracellularly into acrolein and enhances cellular damage by depleting glutathione stores.
Uses of cyclophosphamide in dermatology?
Mycosis fungoides (advanced, FDA approved)
- Off label: ocular cicatricial pemphigoid, severe systemic vasculitides, neutrophilic dermatoses, and autoimmune connective tissue diseases.
How frequent is hemorrhagic cystitis and what causes it in cyclophosphamide administration?
This occurs in 5-41% as a result of acrolein.
- Can be prevented by good hydration and administration of mesna (binds acrolein in blader and reduces irritation)
What are some common side effects of cyclophosphamide administration?
Nausea and vomiting are the most common side effects. Can give ondansetron and dexamethasone to decrease these
What are the long term effects of cyclophosphamide administration and hemorrhagic cystitis and how should they be monitored?
Associated with an increased risk of transitional cell carcinoma of the bladder, non-Hodgkin’s lymphoma, leukemia, and squamous cell carcinoma.
- Monitor with periodic urine analysis with cytologic examination