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Veterinary : Anti-Infective Therapy
Antibiotic/Antifungal/Antiviral
Therapy
Please scroll down for more information on the following topics:
Metronidazole
Esophageal Strictures Secondary to Administration of Doxycycline Tablets
Oral Itraconazole for Therapy of Dermatophytosis Caused by Microsporum
canis
Chloramphenicol Suspension for Birds & Small Animals
Fluoroquinolone Antibiotics
Antibiotic Treats for Feline Abscess
Intranasal Clotrimazole for Treatment of Nasal Aspergillosis in Dogs
Azithromycin
Azithromycin for R. equi Infections in Foals
Idoxuridine Ophthalmic Drops for Cats
Feline Ocular Toxoplasmosis
Itraconazole/DMSO for Fungal Keratitis in Horses
Metronidazole
Metronidazole is effective against a variety of obligate anaerobic bacteria
as well as anaerobic protozoa such as Giardia and Trichomonas. “Various
salts of metronidazole with improved palatability are now available for veterinary
patients... Cats and birds accept the benzoate salt much more willingly than
they accept metronidazole HCl and do not seem to be stressed by its administration.”
Metronidazole should be used with caution in patients with hepatic dysfunction.
Therapy should be promptly discontinued if abnormal neurological signs appear,
including nystagmus, ataxia, seizures, and rigidity. All benzene moieties must
be conjugated with glucuronide to facilitate elimination and this pathway is
inefficient in cats. Therefore, doses of metronidazole benzoate above 200 mg/kg/day
may produce signs of cumulative toxicity in cats within 48 to 72 hours.
Compendium Dec. 2000: 22(12); pp. 1104, 1105, 1107, 1130
Esophageal Strictures Secondary to Administration of Doxycycline Tablets
“The most common causes of esophageal strictures in dogs and cats are gastroesophageal
reflux during anesthesia, persistent vomiting, or ingestion of foreign bodies
or caustic agents. In humans, esophageal retention of oral medication is a common
cause of severe esophagitis. Of the medications proven to lead to esophageal
ulceration, doxycycline is most often implicated. It has been suggested that
pill-induced esophagitis also could occur in small animals...” Drug-induced
esophageal ulceration usually occurs when tablets are taken with little or no
water and adhere to the esophageal mucosa. Once this occurs, flushing with large
quantities of liquid fails to wash the medication into the stomach. Melendez
et al. of Colorado State University College of Veterinary Medicine report on
three cases of presumptive doxycycline-induced esophagitis in cats, with resultant
stricture formation. All cats had been administered fractions of doxycycline
tablets one to three weeks before presenting with a chief complaint of regurgitation. “Two
of the cases developed regurgitation within 7 days after initiation of therapy
with doxycycline. One cat, which was treated while at an animal shelter, was
noted to be regurgitating the day that it was adopted, approximately 2 weeks
after being treated with doxycycline. No other cause of esophageal stricture
formation could be identified.” If a pet that has received a doxycycline
tablet shows sign of esophagitis (dysphagia, excessive salivation, inappetence,
and regurgitation), the doxycycline tablets should be discontinued. Suggested
therapy for esophagitis includes sucralfate slurries, a prokinetic agent (i.e.
cisapride) to increase lower esophageal sphincter tone, and anti-inflammatory
doses of glucocorticoids to prevent stricture formation.
Feline Practice 28:2; 10-12 (Mar/Apr 2000)
Doxycycline can be compounded as a stable flavored liquid preparation or other
palatable dosage form to meet the specific needs of each animal and owner.
Oral Itraconazole for Therapy of Dermatophytosis Caused
by Microsporum canis
Itraconazole could be an effective alternative to griseofulvin that has toxic
effects (particularly in puppies based on this author’s experience)
and frequent therapeutic relapses. Itraconazole has also been used to successfully
treat M. canis infection of cats and guinea pigs.
J Am Vet Med Assoc 1998;213:993-995
Chloramphenicol Suspension for Birds & Small Animals
by J. Terry McGrath, VMD, Pennsylvania
Since chloramphenicol palmitate is no longer commercially available, we contacted
our compounding pharmacist for an alternative for use in our avian and other
small patients, such as rabbits and rodents. The pharmacist prepared a cola
flavored suspension containing 30 mg/ml of chloramphenicol palmitate, which
could be administered using a small oral syringe. However, birds did not
like the taste and it was reformulated into a tutti fruitti and pina colada
syrup. The “animal appropriate” flavor has really helped with compliance,
because now the birds and small animals like to take their medicine!
Note: To avoid potential antagonism, chloramphenicol should not be administered
simultaneously with penicillin or streptomycin. Chloramphenicol-containing
preparations should not be administered in conjunction with, or two hours
prior to, the induction of general anesthesia with pentobarbital.
When administered orally in dogs, chloramphenicol is well-tolerated, has
high clinical efficacy, and a low incidence of side effects. The recommended
canine dosage is 25 mg/lb of body weight every six hours.
Precautions: Chloramphenicol should be administered cautiously to animals
with hematopoietic dysfunction, or impaired kidney or liver function.
Antibiotic Treats for Feline Abscess
Submitted by: Michael Briggs, Pharm.D. Veterinarian: Rich Marchetti, D.V.M.
Patient: One year old non-castrated short-haired male cat with abscess from
wound received in fight. The owner reported that the cat, who is usually affectionate
and friendly toward the owner and house dog, had been withdrawn, on guard,
and growling for approximately three days. A thorn-like projection near the
tail was found by the owner, who immediately took the cat to the veterinarian.
The cat was anesthetized and the veterinarian cleaned, debrided, and shaved
the area of the wound, and prescribed amoxicillin 100 mg daily for ten days.
The owner was instructed to keep the cat inside for the duration of therapy,
to minimize the risk of superinfection and avoid additional injury.
Medication Problem: The cat refused to take liquids, and was also resistant
to taking tablets (“pilling”). The required dose of antibiotic
was too high for transdermal treatment (due to the amount of gel that would
need to be applied for each dose).
Solution: The veterinarian called our compounding pharmacy and asked if we
could come up with a palatable dosage form. We formulated a fish-flavored chewable
treat containing amoxicillin 100 mg to be given once daily for ten days. This
dosage form offers the advantage of ease of administration, decreases the potential
for dosing errors, and greatly increases patient compliance. The cat readily
consumed the amoxicillin “treat”. The wound did not heal in a ten
day period, so five additional days of therapy were required.
Comment: Our pharmacy has compounded this preparation more than ten times with
a 100% success rate.
Intranasal Clotrimazole for Treatment of Nasal Aspergillosis in Dogs
“Treatment of nasal aspergillosis with systemic antifungal medications,
such as thiabendazole, ketoconazole, and fluconazole, has been disappointing
because the response rate is only 43 to 60%. Response to oral administration
of itraconazole has been approximately 60 to 70%... Topical administration of
the imidazoles, enilconazole, and clotrimazole is more effective than orally
administered antifungal medications.”
Topical administration of clotrimazole resulted in resolution of clinical disease
in 65% of dogs after 1 treatment and 87% of dogs after one or more treatments.
Topical administration of clotrimazole, using either technique, was an effective
treatment for nasal aspergillosis in dogs. Use of non-invasive intranasal infusion
of clotrimazole eliminated the need for surgical trephination of frontal sinuses
in many dogs and was associated with fewer complications. Nasal discharge ceased
in most dogs 2 weeks after topical treatment, and the authors now recommend
re-treatment with clotrimazole if nasal discharge has not improved 2 weeks
after treatment.
“[Damage] of the cribriform plate may contraindicate use of topical treatment;
complications arising from leakage of antifungal medications into the CNS in
dogs with fungal rhinitis have not been evaluated.”
J Am Vet Med Assoc 1998 Aug 15;213(4):501-6
Click
here to access the PubMed abstract of this article.
J Am Anim Hosp Assoc 1998 Nov-Dec;34(6):487-92
Click
here to access the PubMed abstract of this article.
Azithromycin
is a form of erythromycin with improved action against gram-negative organisms,
resistance to acid degradation, improved tissue penetration, and a prolonged
elimination half-life. Azithromycin shows potential for use in veterinary
medicine, particularly in cats and certain avian and exotic species.
“Lacking the prokinetic action of erythromycin, azithromycin appears to
cause fewer GI side effects and is generally well tolerated after oral administration.
Cats appear to tolerate the drug particularly well... Animals with a history
of arrhythmias should be monitored while receiving the drug. Some reduction in
dose may be warranted in patients with hepatic or biliary dysfunction, although
no reduction appears necessary in patients with renal dysfunction.” Please
consult our compounding pharmacist regarding dosing.
Compendium of Continuing Education 23:3 (March 2001), pp. 242-7
Azithromycin for R. equi Infections in Foals
On the basis of pharmacokinetic values, minimum inhibitory concentrations of
R. equi isolates, and drug concentrations in pulmonary epithelial lining
fluid (PELF) and bronchoalveolar cells, a single daily oral dose of 10 mg/kg
may be appropriate for treatment of R. equi infections in foals. Persistence
of high azithromycin concentrations in PELF and bronchoalveolar cells 48
hours after discontinuation of administration suggests that after 5 daily
doses, oral administration at 48-hour intervals may be adequate.
Am J Vet Res 2001 Dec;62(12):1870-5
Click
here to access the PubMed abstract of this article.
The Capsule Report, Mixed Practice/Exotic Edition Jan 2002;15, 10: page 1
Itraconazole/DMSO for Fungal Keratitis in Horses
Fungal keratitis is a serious complication of trauma to the eye. Approximately
one-half of the cases of fungal infections have involved the use of eye ointments
containing corticosteroids after trauma to the globe of the eye.
“Itraconazole is a third generation triazole that has superior penetration
properties and a wide spectrum of activity. A 1% solution of itraconazole in
a 30% DMSO and petroleum base has been shown to reach high concentrations within
the stroma of the cornea when administered every 4 to 6 hours. In general, every
6 hours is suitable for all but Fusarium sp which requires every 4 hour administration.”
Disease which is rapidly ulcerating “should also receive treatment that
helps block the enzymes (collagenase) responsible for ulceration. A 5% acetylcysteine
solution and autologous serum in which 4 mg/ml of EDTA has been added has been
recommended. These need to be instilled hourly for best effect. The antimicrobial
can be added to the serum.”
This information has been abstracted from an article by Robert N. Oglesby,
DVM, which appears on his webpage, “The Horseman’s Advisor.”For
more information, references and complete text, see
www.horseadvice.com/sbs/articles/diseases/skin/infectiouskeratitis.html
Idoxuridine Ophthalmic Drops for Cats
The ocular signs of feline herpesvirus I (FHV-1) infection include bilateral
conjunctivitis, serous ocular discharge which may become mucoid or mucopurulent,
and blepharospasm. If corneal involvement is present, topical antivirals
are prescribed. Research indicates that idoxuridine is effective against
FHV-1. Prolonged contact with the infected tissue is required. The 0.1% solution
must be applied five times daily. Previously marketed as Stoxil®, the
ophthalmic solution is not commercially available at this time.
www.eyevet.info/herpes.html (Michael Zigler, DVM, Cert.V.Ophthal)
Am J Vet Res 1989 Jan;50(1):158-60
Feline Ocular Toxoplasmosis
“The anterior uveitis seen in cats with a positive serum titer to Toxoplasma
gondii may result from immune-mediated mechanisms and not the presence or replication
of the organism itself. As a result, it is unclear whether systemic antitoxoplasmic
therapy is beneficial in these cases.” Michael G. Davidson, DVM, of North
Carolina State University, College of Veterinary Medicine reports in Vet Clin
N Amer, Sep 2000, that he “usually treats cats with ocular lesions and
concurrent systemic findings of toxoplasmosis with systemic clindamycin (12.5
mg/kg PO twice daily for 14-21 days) and anti-inflammatory therapy. Other sources
recommend clindamycin 10-12.5 mg/kg every 12 hours for 4 weeks. Oral trimethoprim-sulfonamide
combination therapy (15 mg/kg every 12 hours for 2 to 4 weeks) can also be used
to treat toxoplasmosis but is less suitable because of potential side effects
caused by folic acid deficiency in cats.2 In T gondii seropositive cats exhibiting
anterior uveitis alone and with no systemic signs, Dr. Davidson recommends topical
steroids and atropine alone. If the cat fails to respond to topical therapy alone
within 1-3 weeks, systemic clindamycin should be added to the treatment regimen.
The rationale for the use of corticosteroids is to suppress the damaging inflammation
in the retina, which may affect vision. Corticosteroids are typically administered
1-2 days after antibiotic therapy has been initiated to allow adequate tissue
levels of the antimicrobial agent to be achieved. [Dr. Davidson] does not recommend
systemic steroids in cats with suspected ocular toxoplasmosis because of the
risk of exacerbating systemic replication of T gondii.”1
Swift and aggressive treatment of uveitis is necessary to avoid such secondary
complications as glaucoma, cataract formation, and retinal degeneration or
detachment.3
1 The Capsule Report 19:10 (Jan 2001), p. 4
2, 3 Compendium of Continuing Education 23:3 (March 2001), pp. 258-66 |
