Veterinary Drug Handbook (VDH) is the reference veterinarians turn to when they want an independent source of information on the drugs that are used in veterinary medicine today.


Note: There is significant controversy regarding the frequency of dosing these drugs. See thepharmacokinetic section above for more information. Unless otherwise noted, doses are forcombined amounts of trimethoprim/sulfa.

Dogs: Dog

For susceptible infections:
a) 30 mg/kg PO or IV q12h (avoid or reduce dose in patients with renal failure; avoid inpregnant or breeding animals (Vaden and Papich 1995)
b) 30 mg/kg q12h (if treating Nocardia, double dose) (Ford and Aronson 1985)
c) 15 mg/kg PO or SQ q12h or 30 mg/kg PO, SQ q24h (Kirk 1989)
d) 30 mg/kg PO or 26.4 mg/kg SQ once daily (Package insert; Tribrissen®¯Coopers)
e) For routine infections: 15 mg/kg PO, SQ bid
For meningitis: 15 mg/kg PO, IV bid-tid
For pneumocystis carinii: 15 mg/kg PO tid for 14 days
For mastitis: 30 mg/kg PO bid for 7 days
For toxoplasmosis: 15 mg/kg PO bid-tid (Morgan 1988)
f) For coccidiosis: 30 mg/kg PO once daily for 10 days (Matz 1995)

Cats: Cat

For susceptible infections:
a) 30 mg/kg PO or SQ q12-24h (Papich 1988)
b) 30 mg/kg q12h (if treating Nocardia, double dose) (Ford and Aronson 1985)
c) For toxoplasmosis: 15 mg/kg PO bid has resulted in resolution of CNS disease in somecats. (Lappin 1995)
Pocket Pets/Rodents:
For empiric antibiotic therapy:
a) 15 - 30 mg/kg PO q12h (Oglesbee 1995)

Cattle: Cattle

For susceptible infections:
a) 44 mg/kg once daily IM or IV using 48% suspension. (Upson 1988)
b) 25 mg/kg IV or IM q24h (Burrows 1980)
c) Calves: 48 mg/kg IV or IM q24h (Baggot 1983)

Horses: Horse

For susceptible infections:
a) 15 mg/kg IV q8-12h (Brumbaugh 1987)
b) Foals: 15 mg/kg IV q12h (dose extrapolated from adult horses) (Caprile and Short1987)
c) 22 mg/kg IV q24h or 30 mg/kg PO q24h (Upson 1988)
d) 30 mg/kg PO once daily or 21.3 mg/kg IV once daily (Package inserts;
e) 24 mg/kg PO, IV or IM q12h (Baggot and Prescott 1987)

Swine: Swine

For susceptible infections:
a) 48 mg/kg IM q24h (Baggot 1983)

Birds: Bird

For susceptible infections:
a) Using TMP/SMX oral suspension (240 mg/5 ml): 2 ml/kg PO bid. Good for manygram positive and negative enteric and respiratory infections, particularly in hand-fedbabies. May cause emesis in macaws. (McDonald 1989)
b) For respiratory and enteric infections in psittacines using the 24% injectable suspension: 0.22 ml/kg IM once to twice daily.
For coccidiosis in toucans and mynahs using TMP/SMX oral suspension (240 mg/5ml): 2.2 ml/kg once daily for 5 days. May be added to feed.
For respiratory and enteric infections in hand-fed baby psittacines using TMP/SMXoral suspension (240 mg/5 ml): 0.22 ml/30 grams bid to tid for 5-7 days. (Clubb 1986)
c) Using oral suspension: 50 -100 mg/kg (of combined product) PO q12h (Hoeffer 1995)

Reptiles: Reptile

For susceptible infections:
a) For most species: 30 mg/kg IM (upper part of body) once daily for 2 treatments, thenevery othe day for 5-12 treatments. May be useful for enteric infections. (Gauvin 1993)
Monitoring Parameters -
  • 1) Clinical efficacy
  • 2) Adverse effects; with chronic therapy, periodic complete blood counts should be considered.
  • 3) Thyroid function tests should be considered (baseline and ongoing) particularly in dogs recieving long term treatment
    Client Information - If using suspension, shake well before using. Does not need to be refrigerated. Animals must be allowed free access to water and must not become dehydrated while ontherapy.
    Dosage Forms/Preparations/FDA Approval Status/Withholding Times - Veterinary-Approved Products:
    Trimethoprim (TMP)/Sulfadiazine (SDZ) Oral Tablets:30's: 5 mg TMP/25 mg SDZ (coated tablets)120's: 20 mg TMP/100 mg SDZ (coated tablets)480's: 80 mg TMP/400 mg SDZ (uncoated, scored tablets)960's: 160 mg TMP/800 mg SDZ (uncoated, unscored tablets)
    Tribrissen® (Schering), (Rx) Approved for use in dogs.
    Trimethoprim (TMP)/Sulfadiazine (SDZ) Oral Paste. Each gram contains 67 mg trimethoprimand 333 mg sulfadiazine. Available in 37.5 gram (total weight) syringes.; Tribrissen® 400
    Oral Paste (Schering) (Rx) Approved for use in horses.
    In Canada, trimethoprim and sulfadoxine are available for use in cattle and swine(Trivetrin®¯Wellcome; Borgal®¯Hoechst). They have a slaughter withdrawal of 10 daysand milk withdrawal of 96 hours.

    Human-Approved Products:

    Trimethoprim (alone) Tablets: 100 mg and 200 mg; Proloprim® (Glaxo Wellcome); Trimpex®(Roche); generic, (Rx)
    Trimethoprim 80 mg and Sulfamethoxazole 400 mg Tablets; Trimethoprim 160 mg and Sulfamethoxazole 800 mg Tablets; Bactrim®, Bactrim-DS® (Roche); Septra®, Septra® DS, (Glaxo Wellcome); Cotrim®, Cotrim-DS® (Lemmon), generic; (Rx)
    Trimethoprim 8 mg/ml and Sulfamethoxazole 40 mg/ml oral suspension in pint bottles; Bactrim
    Pediatric® (Roche); Septra® (Glaxo Wellcome); Cotrim Pediatric® (Lemmon) (Rx),
    Sulfatrim, generic (Rx); generic; (Rx)
    Trimethoprim 16 mg/ml and Sulfamethoxazole 80 mg/ml for IV infusion in 5, 10, 20 and 30 mlvials ; Bactrim® IV(Roche); Septra® IV(Glaxo Wellcome); generic (Rx)
    Because of the unavailability of veterinary trimethoprim/sulfadiazine injection in the USA, thehuman injectable product has been used. Before giving IV, the product must be diluted, generally at a rate of 1 ml of TMP/SMZ injection per 25 mls of dextrose 5% injection. Oncediluted the injection should be used within 6 hours. Some reports of administering the drug
    SubQ to ruminants have also been received. To minimize potential local reactions, the injectionshould be diluted at a rate of about 1 ml TMP/SMZ injection to 5 ml dextrose 5%.

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