Niacinamide with tetracycline or doxycycline
Tetracycline is an antibiotic that also modulates the immune system by suppressing neutrophil chemotaxis and lymphocyte activation.65 Tetracycline is used in combination with niacinamide for a variety of immune-mediated dermatologic conditions.
For dogs < 10 kg, 250 mg each of tetracycline and niacinamide are given orally every eight hours. For dogs > 10 kg, the dose
is 500 mg of each every eight hours. Tetracycline and niacinamide are typically not used in cats because it is difficult to
administer these larger-sized oral medications to most cats. Doxycycline has the advantage of needing less frequent dosing
than tetracycline. It has been substituted for tetracycline and used at a dose of 5 to 10 mg/kg orally in dogs every 12 to
24 hours. However, there is no documentation of the benefit of doxycycline when it is substituted for tetracycline to treat
canine pemphigus foliaceus.
Tetracycline and niacinamide appear to be more helpful as a sole therapy in mild cases of pemphigus foliaceus, especially
those cases with lesions localized to the face. It can also be used in combination with glucocorticoids or azathioprine.66 It can take several weeks for tetracycline and niacinamide to have a clinical effect. Once remission occurs with tetracycline
and niacinamide, the frequency of administration can be decreased to once or twice a day.
Side effects include lethargy, anorexia, diarrhea, and increased risk of seizures. Lethargy and anorexia are especially associated
with niacinamide. If the niacinamide needs to be discontinued, the tetracycline (or doxycycline) alone can continue to have
A variety of other therapies have been used for pemphigus foliaceus, including cyclophosphamide, injectable gold salts, intravenous
immunoglobulins, mycophenolate mofetil, and dapsone. Referral to a veterinary dermatologist is recommended before using these
therapies. Referral is also recommended if treatment failure occurs with any of the medications discussed in this article.
No matter which medications are chosen to manage pemphigus foliaceus, frequent recheck examinations are important to assess
clinical response and to determine when to taper medications. We recommend rechecking all pemphigus foliaceus patients within
one or two weeks of starting medical management. A substantial improvement in clinical signs within 10 days of starting glucocorticoid
therapy in dogs is a positive prognostic factor in the successful management of pemphigus foliaceus.5
Glucocorticoids are often used for pemphigus foliaceus treatment induction because of their rapid onset. If marked clinical
improvement is noted, the glucocorticoid dose or frequency of administration should be tapered by about 25%. If clinical signs
have stayed the same or worsened despite glucocorticoid therapy, the glucocorticoid dose should be increased or combination
therapy should be started. Combination therapy should also be started if remission of the pemphigus foliaceus cannot be maintained
when the glucocorticoid dose is tapered. We recommend rechecking patients before and after each change in medication type
or dose to help monitor clinical signs.
Cutaneous side effects of immunosuppression such as a bacterial skin infection, demodicosis, or dermatophytosis can look clinically
similar to a pemphigus foliaceus flare. It is important to rule out these conditions instead of assuming that any new dermatologic
lesions are due to pemphigus foliaceus, otherwise lesions may worsen from immunosuppression, and refractory pemphigus foliaceus
may be erroneously diagnosed. Skin scrapes and hair plucks should be performed on new areas of alopecia, and cytologic examination
should be used to evaluate lesions for secondary skin infections.
Depending on the medication being used to manage the pemphigus foliaceus, blood work may be necessary to monitor for medication
side effects. Regular urine bacterial cultures are recommended for dogs and cats receiving systemic immunosuppressive therapy
to monitor for occult urinary tract infections.5 Urinalysis to identify an active sediment (white blood cells in the urine) is not an effective way to screen for urinary
tract infections in most patients with pemphigus foliaceus because systemic immunosuppression may suppress the number of white
blood cells in the urine even when a urinary tract infection is present. The principles of treating canine and feline pemphigus
foliaceus are summarized in Table 4.
Table 4: Principles of Treating Pemphigus Foliaceus in Dogs and Cats
The outcome of treating pemphigus foliaceus in dogs and cats is variable; 40%51 to 88%4 of dogs with pemphigus foliaceus have their condition managed successfully. Neither a younger age of onset nor a localized
disease pattern correlate with improved survival times.51 The only factor that has influenced long-term survival time in dogs with pemphigus foliaceus is the concurrent use of antimicrobials
with immunosuppressive medications, likely because the antimicrobials minimize the development of secondary bacterial skin
infections and urinary tract infections. Prolonged remission after immunosuppressive therapy can occur in dogs and cats with
Mortality from pemphigus foliaceus can occur because of disease progression, medication side effects, or client-requested
euthanasia. Severe cases of pemphigus foliaceus can result in marked cachexia or sepsis secondary to infections. Adverse effects
are common with most of the medications used for pemphigus foliaceus. Euthanasia accounted for almost 70% of deaths in pemphigus
foliaceus dogs in one retrospective study.51 Reasons for client-requested euthanasia included not being able to control the pemphigus foliaceus, a perceived poor quality
of life, and the development of adverse effects from medications. For all these reasons, pemphigus foliaceus should be considered
a potentially fatal dermatologic condition. Consultation with a specialist or referral can be helpful when managing pemphigus
Pemphigus foliaceus is a pustular and crusting autoimmune dermatologic condition. The prognosis for pemphigus foliaceus in
dogs and cats is variable, and signs can wax and wane. A diagnosis is based on the patient's clinical history, a histologic
examination of skin samples, and a diagnostic work-up that rules out other neutrophilic and pustular skin conditions. A variety
of immunomodulatory medications can be used to manage pemphigus foliaceus. Frequent recheck examinations and client communication
are important for managing pemphigus foliaceus. Because of the potential for severe medication side effects, medications should
be selected and tapered based on the severity of clinical signs.
Kathy C. Tater, DVM, DACVD
Angell Animal Medical Center
350 S. Huntington Ave.
Boston, MA 02130
Thierry Olivry, DrVet, PhD, DECVD, DACVD
Department of Clinical Sciences
College of Veterinary Medicine
North Carolina State University
Raleigh, NC 27606
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