Week 5: Topical Antihistamines, Antipruritics, Scabicides, and Pediculicides Flashcards
Antihistamines exhibit therapeutic effect by:
a) inactivating circulating histamine
b) preventing the production of histamine
c) blocking activity at histamine receptor sites
d) acting as a procholinergic agent
C - blocking activity at histamine receptor sites
A possible adverse effect with the use of a first generation antihistamine such as diphenhydramine in an 80-year-old man is:
a) urinary retention
b) hypertension
c) tachycardia
d) urticaria
A - urinary retention - also narrow-angle glaucoma - because of the anticholinergic effect of this medication
A 78-year-old resident of a long-term care facility complains of generalized itchiness at night that disturbs her sleep. Her examination is consistent with scabies. Which of the following would you expect to find on examination?
a) excoriated papules on the interdigital area
b) annular lesions over the buttocks
c) vesicular lesions in a linear pattern
d) honey-colored crusted lesions that began as vesicles
A - excoriated papules on the interdigital area
In counseling a patient with scabies, the NP recommends all of the following methods to eliminate the mite from bedclothes and other items except:
A) washing items in hot water
B) running items through the clothes dryer for a normal cycle
C) soaking items in cold water for at least 1 hour
D) placing items in a plastic storage bag for at least 1 week
C - soaking items in cold water for at least 1 hour
Which of the following represents the most accurate patient information when using permethrin (Elimite) for treating scabies?
a) to avoid systemic absorption, the medication should be applied over the body and rinsed off within 1 hour.
b) the patient should notice a marked reduction on pruritis within 48 hours of using the product
c) itch often persists for a few weeks after successful treatment
d) it is a second-line product in the treatment of scabes
C - Itch often persists for a few weeks after successful treatment
When advising the patient about scabies contagion, you inform her that:
a) mites can live for many weeks away from the host
b) close personal contact with an infected person is usually needed to contract the disease
c) casual contact with an infected person is likely to result in infestation
d) bedding used by an infected person must be destroyed
B - Close personal contact with an infected person is usually needed to contract this disease
The use of lindane (Kwell) to treat scabies is discouraged because of its potential for:
a) hepatotoxicity
b) neurotoxicity
c) nephrotoxicity
d) pancreatitis
B - neurotoxicity
Benadryl topical mechanism of action
- provides local relief from pruritus and edema because its local effect on the H1-receptors suppresses the the formation of edema, flare, and pruritus
- may also provide local anesthetic activity by decreasing the permeability of the nerve cell membrane to sodium ions, thus blocking the transmission of nerve impulses
Pharmacokinetics of topical Benadryl
- measurable in the serum after topical administration to large areas of the body or on chicken pox or measles, in young children and infants, or when applied to denuded area
- metabolism and excretion are unknown
Topical Benadryl Precautions/ Contraindications
- contraindicated if the patient is sensitive to the medication in any form
- for external use only - contact with the eyes should be avoided
- prolonged used (>7 days) should be avoided
- should not be used to threat chicken pox, measles, poison ivy, or sunburn, or on blistered or oozing skin
- recommended to be used on children > 2 y/o
- Pregnancy Category B
Topical Benadryl ADRs and drug interactions
- may cause skin irritation with prolonged use
- no know drug interactions
- should not be used concurrently with oral or systemic Benadryl
Doxepin Indications and MOA
Used for moderate to severe symptoms - more potent than topical Benadryl
- unclear but is probably related to its H1- and H2-receptor blocking action
- competes at the histamine receptor sites and inhibits activation of histamine receptors
Doxepin Precautions/ Contraindications
- drowsiness in more than 20% of patients using cream, especially on more that 10% of body surface area
- should not be used in patients with untreated narrow-angle glaucoma and urinary retention because of anticholinergic effect, even in the topical form
- contraindicated for use in children
- Pregnancy Category B - use during lactation is not recommended
Doxepin ADRs and drug interactions
- burning and stinging upon application (25% say it is severe)
- Interacts adversely with alcohol, cimetidine, and MAOIs - should be avoided during therapy
- may also interact with any drug that is metabolized by the CYP450 2D6 enzymes
What is the first line treatment for scabies and head lice?
a) Malathione (Ovide)
b) Ivermectin (Sklice)
c) Permethrin
d) Pyrethrins
C - Permethrin
