DƯỢC LÍ Goodman & Gilman's The Pharmacological Basis of Therapeutics 12th, 2010

1818
SECTION IX
SPECIAL SYSTEMS PHARMACOLOGY
diseases. Recommendations for cutaneous antifungal
therapy are summarized in Table 65–8.
The azoles miconazole (MICATIN, others) and
econazole (SPECTAZOLE, others) and the allylamines
naftifine (NAFTIN) and terbinafine (LAMISIL, others) are
effective topical agents for the treatment of localized
tinea corporis and uncomplicated tinea pedis. Topical
therapy with the azoles is preferred for localized cutaneous
candidiasis and tinea versicolor.
Systemic therapy is necessary for the treatment
of tinea capitis or follicular-based fungal infections.
Oral griseofulvin has been the traditional medication
for treatment of tinea capitis. Oral terbinafine is a safe
and effective alternative to griseofulvin in treating tinea
capitis in children (Moosavi et al., 2001).
Tinea Pedis. Topical therapy with the azoles and allylamines is
effective for tinea pedis. Macerated toe web disease may require
the addition of antibacterial therapy. Econazole nitrate, which
has a limited antibacterial spectrum, can be useful in this situation.
Systemic therapy with griseofulvin, terbinafine, or itraconazole
(SPORANOX, others) is used for more extensive tinea pedis.
It should be recognized that long-term topical therapy may be
necessary in some patients after courses of systemic antifungal
therapy.
Onychomycosis. Fungal infection of the nails most frequently is
caused by dermatophytes and Candida. Mixed infections are common.
Because up to one-third of dystrophic nails that appear clinically
to be onychomycosis are actually due to psoriasis or other
conditions, the nail must be cultured or clipped for histological
examination before initiating therapy.
Systemic therapy is necessary for effective management of
onychomycosis. Treatment of onychomycosis of toenails with
griseofulvin for 12-18 months produces a cure rate of 50% and a
relapse rate of 50% after 1 year. Terbinafine and itraconazole offer
significant potential advantages. They quickly produce high drug
levels in the nail, which persist after therapy is discontinued.
Additional advantages include a broader spectrum of coverage with
itraconazole and few drug interactions with terbinafine. Treatment
of toenail onychomycosis requires 3 months with terbinafine (250
mg/day) or itraconazole (200 mg/day). Pulsed dosing with itraconazole
for fingernail onychomycosis consists of 200 mg twice
daily for 1 wk/mo for two pulses. Cure rates of ≥75% have been
achieved with both drugs (Gupta et al., 1994a; Gupta et al., 1994b).
Ciclopirox topical (PENLAC, others) solution is a nail lacquer
that is FDA-approved for the treatment of onychomycosis but demonstrates
low complete cure rates (5.5-8.5%) after 1 year of daily application.
Topical ciclopirox treatment of onychomycosis must include
active removal of the unattached, infected nails as frequently as
monthly.
Antiviral Agents
Viral infections of the skin are very common and
include verrucae (human papillomavirus [HPV]), herpes
simplex virus (HSV), condyloma acuminatum
(HPV), molluscum contagiosum (poxvirus), and
chicken pox (varicella-zoster virus [VZV]). Acyclovir
(ZOVIRAX), famciclovir (FAMVIR, others), and valacyclovir
(VALTREX) frequently are used systemically to
treat HSV and VZV infections (see Chapter 58).
Cidofovir (VISTIDE) may be useful in treating acyclovirresistant
HSV or VZV and other cutaneous viral infections
(Anonymous, 2002a). Topically, acyclovir,
docosanol (ABREVA), and penciclovir (DENAVIR) are
available for treating mucocutaneous HSV. Podophyllin
(25% solution) and podofilox (CONDYLOX, others) 0.5%
solution are used to treat condylomata. The immune
response modifier imiquimod (ALDARA) is discussed in
“Other Immunosuppressive and Anti-Inflammatory
Agents.” Interferons -2b (INTRON A), -n1 (not commercially
available in the U.S.), and -n3 (ALFERON N)
may be useful for treating refractory or recurrent warts
(Carter et al., 2004).
Agents Used to Treat Infestations
Infestations with ectoparasites such as lice and scabies
are common throughout the world. These conditions
have a significant impact on public health in the form of
disabling pruritus, secondary infection, and in the case
of the body louse, transmission of life-threatening illnesses
such as typhus. Topical and oral medications are
available to treat these infestations.
Permethrin is a synthetic pyrethroid that interferes
with insect sodium transport proteins, causing neurotoxicity
and paralysis. Resistance due to mutations in
the transport protein has been reported in Cimex (bed
bugs) and other insects.
The chemical is modeled after the natural insecticide found
in the flower Chrysanthemum cinerariifolium. A 5% cream is available
for the treatment of scabies, and a 1% cream, a cream rinse, and
topical solutions are available OTC for the treatment of lice.
Permethrin is approved for use in infants ≥2 months of age. Other
agents used in the treatment of lice are pyrethrins + piperonyl butoxide
(lotion, gel, shampoo, and mousse) and KLOUT shampoo (acetic
acid + isopropanol).
Lindane (-hexachlorocyclo-hexane) is an organochloride
compound that induces neuronal hyperstimulation
and eventual paralysis of parasites.