Animal Bites in Emergency Medicine Medication

Updated: Oct 07, 2021
  • Author: Alisha Perkins Garth, MD; Chief Editor: Joe Alcock, MD, MS  more...
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Medication Summary

Use of prophylactic antibiotics is one of most controversial subjects in wound care. Proper wound care (inspection, debridement, irrigation, closure if indicated) reduces infection more than antibiotics. In general, low-risk wounds do not require prophylactic antibiotics. However, therapy is recommended for high-risk wounds (eg, cat bites that are a true puncture, bites to the hand, massive crush injury, late presentation, poor general health). [28]

According to 2014 dog and cat bite treatment guidelines from the Infectious Diseases Society of America, preemptive early antimicrobial therapy for 3-5 days is recommended for the following patients [29] :

  • Immunocompromised

  • Asplenic

  • Have advanced liver disease

  • Have preexisting or resulting edema in the affected area

  • Have moderate-to-severe injuries (especially to hand and/or face)

  • Have injuries that may have penetrated the periosteum or joint capsule

The goal of initial therapy is to cover staphylococci, streptococci, anaerobes, and Pasteurella species. Prophylactic antibiotics may be given for a 3- to 5-day course. If the wound is infected on presentation, a course of 10 days or longer is recommended.

The first-line oral therapy is amoxicillin-clavulanate. For higher-risk infections, a first dose of antibiotic may be given intravenously (ie, ampicillin-sulbactam, ticarcillin-clavulanate, piperacillin-tazobactam, or a carbapenem). Other combinations of oral therapy include cefuroxime plus clindamycin or metronidazole, a fluoroquinolone plus clindamycin or metronidazole, sulfamethoxazole and trimethoprim plus clindamycin or metronidazole, penicillin plus clindamycin or metronidazole, and amoxicillin plus clindamycin or metronidazole; a less effective alternative is azithromycin or doxycycline plus clindamycin or metronidazole. [9, 10, 30]

Primate bites, particularly from macaque monkeys, pose a risk of herpes virus B infection. [7] For macaque bites, postexposure prophylaxis with valacyclovir or acyclovir should be given for 14 days after immediate and thorough wound disinfection. [31]



Class Summary

Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting.


Levofloxacin is for pseudomonal infections and infections due to certain multidrug resistant gram-negative organisms.


Metronidazole is an imidazole ring-based antibiotic active against various anaerobic bacteria and protozoa. It is used in combination with other antimicrobial agents (except for Clostridium difficile enterocolitis).

Ampicillin and sulbactam (Unasyn)

Ampicillin and sulbactam is a drug combination of beta-lactamase inhibitor with ampicillin. It interferes with bacterial cell wall synthesis during active replication, causing bactericidal activity against susceptible organisms.

Ticarcillin and clavulanate potassium (Timentin)

The ticarcillin and clavulanate potassium combination inhibits biosynthesis of cell wall mucopeptide and is effective during the stage of active growth. It is an antipseudomonal penicillin plus beta-lactamase inhibitor that provides coverage against most gram-positive organisms, most gram-negative organisms, and most anaerobes.

Piperacillin and tazobactam sodium (Zosyn)

Piperacillin and tazobactam sodium combination is an antipseudomonal penicillin plus beta-lactamase inhibitor. It inhibits the biosynthesis of cell wall mucopeptide and is effective during the stage of active multiplication.

Imipenem and cilastatin (Primaxin)

The combination of imipenem and cilastatin is for treatment of multiple organism infections in which other agents do not have wide-spectrum coverage or are contraindicated due to potential for toxicity.

Ertapenem (Invanz)

Ertapenem has bactericidal activity that results from the inhibition of cell wall synthesis and is mediated through ertapenem binding to penicillin-binding proteins. It is stable against hydrolysis by a variety of beta-lactamases, including penicillinases, cephalosporinases, and extended-spectrum beta-lactamases. Ertapenem is hydrolyzed by metallo-beta-lactamases.

Meropenem (Merrem IV)

Meropenem is a bactericidal broad-spectrum carbapenem antibiotic that inhibits cell-wall synthesis. It is effective against most gram-positive and gram-negative bacteria. Meropenem has slightly increased activity against gram-negatives and slightly decreased activity against staphylococci and streptococci compared with imipenem.

Amoxicillin and clavulanate (Augmentin)

Amoxicillin and clavulanate is a drug combination that extends the antibiotic spectrum of penicillin to include bacteria normally resistant to beta-lactam antibiotics. Amoxicillin and clavulanate is first-line therapy for the prophylactic treatment of dog, human, and cat bites (see Medication Summary above). It is also indicated for skin and skin structure infections caused by beta-lactamase–producing strains of Staphylococcus aureus.

Cefuroxime (Ceftin, Kefurox, Zinacef)

Cefuroxime is a second-generation cephalosporin that maintains gram-positive activity that first-generation cephalosporins have; it adds activity against Proteus mirabilis, Haemophilus influenzae, Escherichia coli, Klebsiella pneumoniae, and Moraxella catarrhalis. The condition of the patient, the severity of infection, and the susceptibility of the microorganism determine proper dose and route of administration.

Ciprofloxacin (Cipro)

Ciprofloxacin is a fluoroquinolone with activity against pseudomonads, streptococci, methicillin-resistant S aureus, Staphylococcus epidermidis, and most gram-negative organisms, but no activity against anaerobes. It inhibits bacterial DNA synthesis and, consequently, growth.

Clindamycin (Cleocin)

Clindamycin is a lincosamide for the treatment of serious skin and soft tissue staphylococcal infections. It is also effective against aerobic and anaerobic streptococci (except enterococci). Clindamycin inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest.

Sulfamethoxazole/trimethoprim (Bactrim, Bactrim DS, Septra, Septra DS)

Sulfamethoxazole/trimethoprim inhibits bacterial growth by inhibiting the synthesis of dihydrofolic acid.

Amoxicillin (Trimox, Biomox, Amoxil)

Amoxicillin alone is effective against Pasteurella species. However, it is not indicated for skin and skin structure infections caused by beta-lactamase–producing strains of S aureus. A second antibiotic, such as cephalexin, is needed for Staphylococcus infections.

Azithromycin (Zithromax)

Azithromycin inhibits bacterial growth, possibly by blocking dissociation of peptidyl tRNA from ribosomes, causing RNA-dependent protein synthesis to arrest. It treats mild-to-moderate microbial infections.

Doxycycline (Doryx, Vibramycin, Bio-Tab)

Doxycycline inhibits protein synthesis and thus bacterial growth by binding to 30S and possibly 50S ribosomal subunits of susceptible bacteria.


Antiviral agents

Class Summary

These agents inhibit viral replication.

Acyclovir (Zovirax)

Acyclovir is a prodrug activated by phosphorylation by virus-specific thymidine kinase that inhibits viral replication. Herpes virus thymidine kinase (TK), but not host cells' TK, uses acyclovir as a purine nucleoside, converting it into acyclovir monophosphate, a nucleotide analogue. Guanylate kinase converts the monophosphate form into diphosphate and triphosphate analogues that inhibit viral DNA replication.

Acyclovir has affinity for viral thymidine kinase and, once phosphorylated, causes DNA chain termination when acted on by DNA polymerase. It has activity against a number of herpesviruses, including herpes virus B. Acyclovir is primarily available in preparations for oral and intravenous use. Patients experience less pain and faster resolution of cutaneous lesions when used within 48 hours from rash onset. Acyclovir may prevent recurrent outbreaks. Early initiation of therapy is imperative.

Valacyclovir (Valtrex)

Valacyclovir is a hydrochloride salt of the L-valyl ester of acyclovir. It is rapidly converted into acyclovir after prompt absorption from the gut via first-pass intestinal or hepatic metabolism. It is an alternative to acyclovir for prophylaxis (or possibly treatment).



Class Summary

Tetanus results from elaboration of an exotoxin from Clostridium tetani. A booster injection in previously immunized individuals is recommended to prevent this potentially lethal syndrome. Patients who may not have been immunized against C tetani products (eg, immigrants, the elderly) should receive tetanus immune globulin.

Tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine (Tdap, Adacel, Boostrix)

The vaccine combination tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine promotes active immunity to diphtheria, tetanus, and pertussis by inducing production of specific neutralizing antibodies and antitoxins. It is indicated for active booster immunization for tetanus, diphtheria, and pertussis prevention for persons aged 10-64 years (Adacel approved for 11-64 y, Boostrix approved for 10-18 y). It is the preferred vaccine for adolescents scheduled for booster.

Tetanus toxoid adsorbed or fluid

The tetanus toxoid vaccine is no longer available in the United States.

It is used to induce active immunity against tetanus in selected patients. The immunizing agent of choice for most adults and children older than 7 years are tetanus and diphtheria toxoids. It is necessary to administer booster doses to maintain tetanus immunity throughout life.

The CDC recommends Td for pregnant patients who have urgent an indication tor tetanus toxoid or diphtheria toxoid vaccination.

In children and adults, it can be administered into deltoid or midlateral thigh muscles. In infants, the preferred site of administration is the mid thigh laterally.


Immune Globulin

Class Summary

Immune globulins are indicated in previously unvaccinated individuals to provide passive immunity to tetanus when individuals become exposed.

Tetanus immune globulin (HyperTET S/D)

Tetanus immune globulin is used for passive immunization of any person with a wound that might be contaminated with tetanus spores.

Rabies Immune Globulin (Imogam Rabies-HT, HyperRab S/D)

Rabies immune globulin provides passive protection to individuals exposed to rabies virus. About half the dose should be administered into and around the bite wound as much as possible (given anatomic constraints), and the rest given intramuscularly at a site remote from the vaccine administration area in the gluteal or deltoid muscle.


Vaccine, Inactivated Virus

Class Summary

Inactivated virus vaccines are inactivated forms of virus that promote immunity by inducing an active immune response.

Rabies vaccine (Rabavert, Imovax Rabies Vaccine)

Rabies vaccine is an inactivated form of virus grown in primary cultures of chicken fibroblasts; it offers active immunity and, when used in combination with human rabies immune globulin (HRIG) and local wound treatment, protects postexposure patients of all age groups; it is also used for preexposure immunization in both the primary series and booster dose.

Fourteen days after initiating immunization series, anti-rabies antibody titers reach levels well abovethe minimal protective level of 0.5 IU/mL.

The vaccine must be injected intramuscularly and never SC, ID, or IV. In adults, inject into the deltoid muscle area. In small children, administer into the anterolateral zone of the thigh.

Rabies vaccine (HDCV, Imovax, Rabies vaccine human diploid cell culture)

Rabies vaccine adsorbed is an inactivated virus vaccine that promotes immunity by inducing active immune response. Rabies vaccine is given intramuscularly only, never intradermally.