Cat Bites & Amoxicillin?
Adam Sundor
snip...last part of what Shelly wrote:
P. Multocida is part of the natural flora of cats' mouths.
The treatment of choice for a cat bite is Pen V or
Augmentin (amoxicillin clavulanate). Pen allergic patients
can use doxycycline. Ceftriaxone is also an alternative,
but according to Sanford not the first alternative.
Shelly, a non-compassionate human doctor (don't believe
there is a study comparing animal versus human physicians)
Shelly
According to Micromedex, a computerized database for
Disease and Trauma Reviews, a drug of choice is not
amoxicillin because it's "expensive, no more effective than
dicloxacillin and has a high incidence of adverse affects."
Perhaps someone can help explain this difference between
what I read and what Shelly wrote. Could it be that
amoxicillin is the drug of choice for birds, and not people
then? This was my original query, really, for birds.
I have enclosed a lengthy quote for those
interested. By the way, there are 144 references at the
end for further perusal. I enclosed the last few for
brevity's sake. It appears that one of these sources is
perhaps out of date. I would tend to trust Micromedex, but
I await further comment.
First to summarize, Micromedex says:
(a) Dicloxacillin and cephalexin are drugs of
choice; effective for most potential pathogens but less
efficacy against P multocida.
(e) Amoxicillin-clavulanic acid has good spectrum
and is effective for P multocida but is no more effective
than dicloxacillin, is expensive, and has high incidence of
adverse effects.
Now for the fuller version for those who care to read more
detail than the above. This is rather lengthy but if this
helps determine the drugs of choice in cat bites, maybe I
will be forgiven for taking up so much bandwidth:
3. BITE, CAT
a. OVERVIEW
(1) GENERAL: Wound type and depth are important risk factors for cat-bite
wound infections, regardless of whether or not the patient received prophylactic
oral antibiotics. Risk is particularly high in patients with lower extremity
and puncture wounds who do not receive antibiotic prophylaxis (Dire, 1991).
(2) PATHOGENS: Pasteurella multocida is major pathogen; infection can
become symptomatic within 12 hours and spread rapidly. Also S aureus.
(3) INDICATIONS:
(a) PROPHYLAXIS: High-risk wounds (probability of infection >5% to 10%):
bites with full-thickness puncture, hand, or lower extremity wounds; bites
requiring surgical debridement, involving joints, tendons, ligments, or
fractures, and in high-risk hosts (Dire, 1992a; Callaham, 1991). Not
recommended routinely for uninfected cat scratches (Dire, 1991).
(b) TREATMENT: All overtly established wound infections.
(4) TIMING (Prophylaxis): Initial dose must be given as early in patient's
treatment as possible (within 3 to 4 hours of bite), preferably parenterally
during triage on entry to ED (Callaham, 1991; Dire, 1992a).
(5) DRUGS OF CHOICE: Same for both prophylaxis and therapy. Use
parenteral drugs for loading dose (outpatients) and for hospitalized patients
(Dire, 1992a; Callaham, 1991).
(a) Dicloxacillin and cephalexin are drugs of choice; effective for most
potential pathogens but less efficacy against P multocidas.
(b) Penicillin is excellent for P multocida but is not optimal for many
other significant pathogens.
(c) Tetracycline is alternative choice for adults allergic to both
penicillins and cephalosporins.
(d) Erythromycin is alternative choice for prophylaxis in patients
allergic to both penicillins and cephalosporins; not recommended for established
P multocida infections because of possible treatment failures.
(e) Amoxicillin-clavulanic acid has good spectrum and is effective for P
multocida but is no more effective than dicloxacillin, is expensive, and has
high incidence of adverse effects.
b. NAFCILLIN
(1) INDICATIONS: A drug of choice for (Callaham, 1991; Dire, 1992a):
recommended routinely for uninfected cat scratches (Dire, 1991).
(b) TREATMENT: All overtly established wound infections.
(4) TIMING (Prophylaxis): Initial dose must be given as early in patient's
treatment as possible (within 3 to 4 hours of bite), preferably parenterally
during triage on entry to ED (Callaham, 1991; Dire, 1992a).
(5) DRUGS OF CHOICE: Same for both prophylaxis and therapy. Use
parenteral drugs for loading dose (outpatients) and for hospitalized patients
(Dire, 1992a; Callaham, 1991).
(a) Dicloxacillin and cephalexin are drugs of choice; effective for most
potential pathogens but less efficacy against P multocida.
(b) Penicillin is excellent for P multocida but is not optimal for many
other significant pathogens.
(c) Tetracycline is alternative choice for adults allergic to both
penicillins and cephalosporins.
(d) Erythromycin is alternative choice for prophylaxis in patients
allergic to both penicillins and cephalosporins; not recommended for established
P multocida infections because of possible treatment failures.
(e) Amoxicillin-clavulanic acid has good spectrum and is effective for P
multocida but is no more effective than dicloxacillin, is expensive, and has
high incidence of adverse effects.
b. NAFCILLIN
(1) INDICATIONS: A drug of choice for (Callaham, 1991; Dire, 1992a):
(a) Initial dose before initiating outpatient oral prophylaxis of
uninfected high-risk cat bite wounds or treatment of infected wounds. For
prophylaxis, must be given as early in patient's treatment as possible (within 3
to 4 hours of bite), preferably parenterally during triage on entry to ED.
(b) Initial inpatient therapy for infections without sepsis, pending
culture results (given with penicillin G).
(2) RECOMMENDATION:
(a) OUTPATIENTS (Loading dose): 1 to 2 grams (children: 25 to 50
milligrams/kilogram) intravenously in a single dose, FOLLOWED BY dicloxacillin
(Callaham, 1991; Dire, 1992a).
(b) INPATIENTS: 1 to 2 grams (children: 25 to 50 milligrams/kilogram)
intravenously every four hours, PLUS penicillin G, pending results of wound
culture (Dire, 1992a).
(3) AVAILABLE FORMS: Unipen(R) (injection); Nafcil(R) (injection).
(4) DOSING IN SPECIAL SITUATIONS: Dosing adjustment not required in renal
failure.
(5) MAJOR ADVERSE REACTIONS: Hemolytic anemia and neurotoxicity
(convulsions) with large IV doses; allergic reactions, including anaphylaxis;
interstitial nephritis (hypersensitivity reaction).
(6) PRECAUTIONS: Contraindicated in penicillin allergy; use with caution
in patients with other suspected allergies.
c. DICLOXACILLIN
(1) INDICATIONS (Callaham, 1991; Dire, 1992a):
(a) A drug of choice for prophylaxis of high-risk uninfected cat bite
wounds or treatment of infected wounds; effective for most potential pathogens
but less efficacy against P multocida.
(b) For prophylaxis, initial dose must be given as early in patient's
treatment as possible (within 3 to 4 hours of bite), preferably parenterally
during triage on entry to ED (use antistaphylococcal drug, eg, nafcillin).
(2) RECOMMENDATION (Following initial parenteral dose) (Dire, 1992a;
Callaham, 1991):
(a) PROPHYLAXIS: 500 milligrams orally four times daily (children: 50 to
100 milligrams/kilogram/day orally in four divided doses) for 3 to 5 days.
(b) TREATMENT: 500 milligrams orally four times daily (children: 50 to
100 milligrams/kilogram/day orally in four divided doses) for 5 to 7 days, or
until clinically free of infection.
(3) AVAILABLE FORMS: Dynapen(R) (capsules); Pathocil(R) (capsules).
(4) DOSING IN SPECIAL SITUATIONS: Dose adjustment not required in renal
insufficiency.
(5) MAJOR ADVERSE REACTIONS: Allergic reactions, including anaphylaxis;
hepatotoxicity (cholestatic jaundice); leukopenia.
(6) PRECAUTIONS: Contraindicated in patients with known penicillin
allergy.
d. CEFAZOLIN
(1) INDICATIONS: A drug of choice for initial dose before initiating
outpatient oral prophylaxis of uninfected high-risk cat bite wounds or treatment
of infected wounds (Callaham, 1991; Dire, 1992a).
(2) RECOMMENDATION (Loading dose): 1 gram (children: 25
milligrams/kilogram) intravenously or intramuscularly in a single dose, FOLLOWED
BY cephalexin (Callaham, 1991; Dire, 1992a).
(3) AVAILABLE FORMS: Ancef(R) (injection); Kefzol(R) (injection).
(4) DOSING IN SPECIAL SITUATIONS: Reduce dose in patients with renal
insufficiency.
(5) MAJOR ADVERSE REACTIONS: Hypersensitivity reactions (fever, rash,
eosinophilia); blood dyscrasias; pain at injection site with IM use.
(6) PRECAUTIONS: Contraindicated in patients hypersensitive to
cephalosporins; caution in patients with impaired renal function or penicillin
allergy; can cause false-positive with Clinitest(R) and false-positive Coombs'
test results.
7. MONITORING PARAMETERS: Serum concentrations for severe infections
(above 2 mcg/mL).
e. CEPHALEXIN
(1) INDICATIONS (Callaham, 1991; Dire, 1992a):
(a) A drug of choice for prophylaxis of high-risk uninfected cat bite
wounds or treatment of infected wounds; effective for most potential pathogens
but less efficacy against P multocida.
(b) For prophylaxis, initial dose must be given as early in patient's
treatment as possible (within 3 to 4 hours of bite), preferably parenterally
during triage on entry to ED (use first-generation cephalosporin, eg,
cefazolin).
(2) RECOMMENDATION (Following initial parenteral dose) (Dire, 1992a;
Callaham, 1991):
(a) PROPHYLAXIS: 500 milligrams orally four times daily (children: 50 to
100 milligrams/kilogram/day orally in four divided doses) for 3 to 5 days.
(b) TREATMENT: 500 milligrams orally four times daily (children: 50 to
100 milligrams/kilogram/day orally in four divided doses) for 5 to 7 days, or
until clinically free of infection.
(3) AVAILABLE FORMS: Keflex(R) (capsules, tablets) or equivalent
cephalosporin.
(4) DOSING IN SPECIAL SITUATIONS: Reduce dose in renal failure; dose
adjustments not required in hepatic insufficiency.
(5) MAJOR ADVERSE REACTIONS: Severe diarrhea; allergic reactions; blood
dyscrasias (rare).
(6) PRECAUTIONS: Caution in patients with history of penicillin allergy
and renal failure; discontinue if persistent diarrhea occurs; concomitant
probenecid increases serum levels.
f. PENICILLIN G
(1) INDICATIONS: Excellent for P multocida but is not optimal for many
other significant pathogens. A drug of choice for (Callaham, 1991; Dire,
1992a):
(a) Initial dose before initiating outpatient oral prophylaxis of
uninfected high-risk cat bite wounds or treatment of infected wounds. For
prophylaxis, must be given as early in patient's treatment as possible (within 3
to 4 hours of bite), preferably parenterally during triage on entry to ED.
(b) Initial inpatient therapy for infections without sepsis, pending
culture results (given with nafcillin).
(2) RECOMMENDATION:
(a) OUTPATIENTS (Loading dose): 1.2 million units (children: 25,000
units/kilogram) intravenously or intramuscularly in a single dose, FOLLOWED BY
penicillin V (Callaham, 1991; Dire, 1992a).
(b) INPATIENTS: 1 to 2 million units/day (children: 100,000
units/kilogram/day) intravenously in four to six divided doses, PLUS nafcillin,
pending results of wound culture (Dire, 1992a).
(3) AVAILABLE FORMS: Pfizerpen(R) (injection).
(4) DOSING IN SPECIAL SITUATIONS: Reduce dose in elderly patients and in
patients with reduced renal function.
(5) MAJOR ADVERSE REACTIONS: Hemolytic anemia and neurotoxicity
(convulsions) with large IV doses; allergic reactions, including anaphylaxis;
cardiac arrest following massive IV doses, particularly in patients with renal
failure; interstitial nephritis (hypersensitivity reaction).
(6) PRECAUTIONS: Contraindicated in patients with penicillin allergy;
caution in patients with cephalosporin hypersensitivity, impaired renal
function, or pre-existing seizure disorders.
g. PENCILLIN V
(1) INDICATIONS (Callaham, 1991; Dire, 1992a):
(a) A drug of choice for prophylaxis of high-risk uninfected cat bite
wounds or treatment of infected wounds; excellent for P multocida but is not
optimal for many other significant pathogens.
(b) For prophylaxis, initial dose must be given as early in patient's
treatment as possible (within 3 to 4 hours of bite), preferably parenterally
during triage on entry to ED (use penicillin G).
(2) RECOMMENDATION (Following initial parenteral dose) (Dire, 1992a;
Callaham, 1991):
(a) PROPHYLAXIS: 500 milligrams orally four times a day (children: 50 to
100 milligrams/kilogram/day orally in four divided doses) for 3 to 5 days.
(b) TREATMENT: 500 milligrams orally four times daily (children: 50 to
100 milligrams/kilogram/day orally in four divided doses) for 5 to 7 days, or
until clinically free of infection.
(3) AVAILABLE FORMS: Pen Vee K(R) (tablets, oral solution).
(4) DOSING IN SPECIAL SITUATIONS: Reduce dose in severe renal
insufficiency.
(5) MAJOR ADVERSE REACTIONS: Allergic reactions, including anaphylaxis;
blood dyscrasias (rare).
(6) PRECAUTIONS: Contraindicated in patients with known penicillin
allergy; caution in patients with history of allergies or asthma; probenecid
prolongs serum half-life; avoid with oral neomycin.
h. ERYTHROMYCIN
(1) INDICATIONS:
(a) PROPHYLAXIS: Alternative choice for prophylaxis of high-risk
uninfected cat bite wounds in patients allergic to both penicillins and
cephalosporins (Callaham, 1991; Dire, 1992a).
(b) TREATMENT: Has poor in vitro activity and has been associated with
serious clinical failures; not recommended for empiric treatment of established
animal bite wound infections (Levin, 1990). However, may be only choice in
pregnant patients and patients allergic to both penicillins and cephalosporins.
(2) RECOMMENDATION (Callaham, 1991a):
(a) PROPHYLAXIS: 500 milligrams orally four times daily (children: 30 to
50 milligrams/kilogram/day orally in four divided doses) for 3 to 5 days.
(b) TREATMENT: 500 milligrams orally four times daily (children: 30 to 50
milligrams/kilogram/day orally in four divided doses) for 5 to 7 days, or until
clinically free of infection.
(3) AVAILABLE FORMS: Ilosone(R) (capsules); Erythrocin(R) (tablets), many
other preparations.
(4) DOSING IN SPECIAL SITUATIONS: Reduce dose in liver insufficiency;
dose reduction not required in renal insufficiency.
(5) MAJOR ADVERSE REACTIONS: Hepatotoxicity with estolate salt; allergic
reactions; abdominal cramps; hearing loss (IV infusion, large doses).
(7) PRECAUTIONS: Use with caution in liver disease; may increase
theophylline serum levels and toxicity during concomitant therapy.
i. TETRACYCLINE
(1) INDICATIONS: Alternative choice for treatment of infected cat bite
wounds in adults allergic to penicillins and cephalosporins (Callaham, 1991;
Dire, 1992a).
(2) RECOMMENDATION: 500 milligrams orally four times daily (children over
eight years: 25 to 50 milligrams/kilogram/day orally in four divided doses) for
at least seven days (Brook, 1989; Med Lett, 1992).
(3) AVAILABLE FORMS: Sumycin(R) (250-, 500-mg capsules); many other
preparations.
(4) DOSING IN SPECIAL SITUATIONS: Dosage interval should be increased in
patients with renal insufficiency; dose reductions indicated in hepatic disease
and in elderly patients.
(5) MAJOR ADVERSE REACTIONS: Hepatic failure and nephrotoxicity following
large IV doses (>2 gm/day); adverse reactions with long-term use.
(6) PRECAUTIONS: Contraindicated in pregnancy and in children under 8 yrs
of age; use with caution in renal impairment and liver disease; milk and dairy
products and iron salts can significantly reduce absorption of tetracycline;
increased azotemia in patients with renal insufficiency receiving diuretics.
(7) MONITORING PARAMETERS: Renal function tests, hepatic function tests.
j. AMOXICILLIN/CLAVULANIC ACID
(1) INDICATIONS:
(a) Alternative drug for prophylaxis of high-risk uninfected cat bite
wounds or treatment of infected wounds; covers both P multocida and S aureus
(Tandberg, 1990; Stucker, 1993); however, some authorities do not recommend it
for initial antimicrobial therapy because it is no more effective than
dicloxacillin, is expensive, and has high incidence of adverse effects
(Callaham, 1991; Dire, 1992a).
(b) For prophylaxis, initial dose must be given as early in patient's
treatment as possible (within 3 to 4 hours of bite), preferably parenterally
during triage on entry to ED (use penicillin G).
(2) RECOMMENDATION (Stucker, 1990; Tandbert, 1990):
(a) PROPHYLAXIS: 500 milligrams orally four times daily (children: 20 to
40 milligrams/kilogram/day orally in four divided doses) for 3 to 5 days.
(b) TREATMENT: 500 milligrams orally three times daily (children: 20 to
40 milligrams/kilogram/day orally in three divided doses) for 5 to 7 days, or
until clinically free of infection.
(3) AVAILABLE FORMS: Augmentin(R) (tablets, suspension).
(4) DOSING IN SPECIAL SITUATIONS: Reduce dose in renal failure.
(5) MAJOR ADVERSE REACTIONS: Nausea, vomiting, diarrhea (greater than
with amoxicillin alone); rash, including erythema multiforme; blood dyscrasias.
(6) PRECAUTIONS: Contraindicated in penicillin-allergic patients; caution
in renal failure, gastrointestinal disorders; may interfere with Clinintest(R)
(use Clinistix(R) or Testape(R)).
4. IMMUNODEFICIENCY
a. OVERVIEW
(1) INDICATIONS: High-risk host due to (Callaham, 1991):
(a) Asplenism.
(b) Altered immune status (chemotherapy, HIV infection, immune defect).
(c) Diabetes.
(d) Chronic corticosteroid therapy.
(e) Prosthetic or diseased joint or cardiac valve.
(2) TIMING (Prophylaxis): Initial dose must be given as early in patient's
treatment as possible (within 3 to 4 hours of bite), preferably parenterally
during triage on entry to ED (Callaham, 1991; Dire, 1992a).
(3) DRUGS OF CHOICE: Same for both prophylaxis and therapy; a second- or
third-generation cephalosporin (eg, cefuroxime, ceftriaxone) is drug of choice.
Use parenteral drugs for loading dose (outpatients) and for hospitalized
patients (Callaham, 1991).
b. CEFUROXIME
(1) INDICATIONS (Callaham, 1991):
(a) Prophylaxis of uninfected bites or treatment of clinically infected
organism may be responsible for bacteremia secondary to animal bites.
Significant possibilities include Bacteroides sp, Proteus, Klebsiella, Eikenella
corrodens, Pseudomonas sp, Enterobacter sp, Pasteurella multocida,
Streptococcus, Aeromonas hydrophila, and alpha-numeric types EF-4, DF-2, II-J,
and M-5 (Callaham, 1991).
(b) Aerobic and anaerobic wound and blood cultures should be obtained
(Dire, 1992a).
(2) EMPIRIC THERAPY: After cultures are obtained but before the pathogen
is identified, broad-spectrum antibiotic therapy should be started with a
third-generation cephalosporin (eg, ceftriaxone or cefotaxime). Alternatively,
combination therapy with a first-generation cephalosporin plus an aminoglycoside
(eg, cefazolin plus gentamicin) may be used.
(3) MORE SPECIFIC ANTIBIOTIC COVERAGE: Based on results of initial culture
and sensitivity reports (Med Lett, 1992):
(a) AEROMONAS: Cotrimoxazole, aminoglycoside, imipenem, fluoroquinolone.
(b) DF-2: Penicillin, cefazolin, clindamycin.
(c) BACTEROIDES: Penicillin G, clindamycin, cefoxitin, metronidazole,
cefotetan.
(d) PSEUDOMONAS: Ticarcillin plus tobramycin, ceftazidime.
(e) STAPHYLOCOCCUS AUREUS: Nafcillin (or equivalent), cefazolin.
(f) PASTEURELLA MULTOCIDA: Penicillin G, cefazolin.
b. CEFTRIAXONE
....
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Orrmom
Micromedex. Micromedex is a computerized data base available to lots of
folks covering a large range of medications. I use it if I want to know a
little in a pinch about a medication I have never heard of. It is a
compilation of a lot of materials. It can be interesting to read and will
do in a pinch, but (ask your own doctor) not what most of us use to make
our antibiotic choices. It is nice that they factor cost into their
decision making process, but lets clear one thing up, amoxicillin is an
incredibly cheap drug has lots of good uses, and once was considered
fairly broad spectrum but because of antibiotic resistance, is no longer.
With the addition of clavulanic acid you increase your spectrum. You also
increase the cost significantly. Ask any parent who has to use augmentin
for their childs ear infection.
"Sanford" refers to a handy little book called "Guide to Antimicrobial
Therapy". It is edited by Dr. Jay Sanford a specialist in infectious
disease. For the physician who does not specialize in ID, it is an
essential reference. If you look closely at your micromedex, you may find
that it most likely refers to Dr. Sanford in its bibliography, if not in
this particular passage,than certainly in other areas pertaining to ID.
_This_ is the reference your physician uses, not usually micromedex. Once
again, it's good for general good information, but no resource in medicine
is complete all by itself. So let's look in other sources, shall we.
Handbook of Antimicrobial therapy lists for treatment #1
amoxicillin-clavulanate
#2 ampicillin-sulbactam(this is an iv preparation) or in pen allergic
patients-tetracycline. Harrison's Principles of Internal Medicine also
list Amox-Clavulanate as treatment of choice. Cefoxitine is #2 and for
the pen allergic patient tetracycline is the alternative.
There are also contraindications to taking tetracyclines. It absolutely
can not be given to children nor to pregnant women. It is malabsorbed if
taken with dairy products or antacids so must be taken on an empty
stomach. As an annecdotal aside nothing will make me puke faster than a
doxycycline on an empty stomach.
Doxy is a fine drug, don't get me wrong. It has many excellent uses
including the ability to use it in animal bites. It is _not_ as broad
spectrum as amox-clav. I really don't argue your point about the ability
to use this drug. Every reference I have read claims better killing
ability with the other drugs. When it comes right down to it, I hesitate
to use a treatment if it only "saves money". Cheap is not everything.
I'd rather save life and limb.
Shall I use my real credentials this time?
Michelle Orr MD (Board Certified in Internal Medicine--consider it the
adult human equivilent to getting that avian certificate)
Shelly