Primor 240mg Tab (per tablet) | On Sale | EntirelyPets Rx
Licensed U.S. Pet Pharmacy | Verified Pharmacy
Mobile Menu
Search Submit
Live Chat My Account
View Cart 0
  • Product ImageProduct Image
  • Product ImageProduct Image
  • Product ImageProduct Image

Primor 240mg Tab (per tablet)

Item# HA240MGPT
FREE SHIPPING Over $79! * Pet Food & Other Exclusions
1. Select strength:
2. Select count (tablets):

Price too low to show

Add to cart to see low price
  1. We'll ask for your vet's info during check out.
  2. We'll verify your prescription and ship your order! Learn more >>
  • Description
  • Ingredients
  • Directions
  • FAQ
  • Reviews


Primor is an antimicrobial drug containing sulfadimethoxine and ormetoprim in a 5 to 1 ratio. The combination of these 2 compounds results in the potentiation of sulfadimethoxine, providing increased efficacy, a broadened spectrum of activity to include some sulfonamide resistant organisms, and reduction in the rate of resistance development.

Key Benefits

  • Treats skin and soft tissue infections (wounds and abscesses)
  • Also effective against urinary tract infections caused by susceptible bacteria
  • Single, comparatively low dose provides rapid and sustained therapeutic blood levels

How it works

Primor is made up of two antibiotics: sulfadimethoxine and ormetoprim. Together, these antibiotics are even more powerful than when they are used alone, as they block two sequential steps in bacterial folic acid synthesis. The net effect is not only the limiting of bacterial growth, but the killing of bacteria as well.


Primore is for the treatment of skin and soft tissue infections (wounds and abscesses) in dogs caused by strains of Staphylococcus aureus and Escherichia coli and urinary tract infections caused by Escherichia coli, Staphylococcus spp., and Proteus mirabilis susceptible to sulfadimethoxine/ormetoprim.



Sulfadimethoxine, Ormetoprim.


View Primor product label.

Administer an initial oral dose of 25 mg/lb (55 mg/kg) of body weight on the first day of treatment. Administer subsequent daily doses at the rate of 12.5 mg/lb (27.5 mg/kg) of body weight. Continue treatment for at least 2 days after remission of clinical signs. Do not extend treatment for more than 21 consecutive days. Suggested dosage schedules follow:

Body Weight (lb) Up To No. of Tablets First Day No. of Tablets Subsequent Days
Primor 120 5 1 ½
10 2 1
15 3 1 ½
Primor 240 10 1 ½
20 2 1
30 3 1 ½
Primor 600 25 1 ½
50 2 1
Primor 1200 50 1 ½
100 2 1

For optimal therapeutic effect: (1) the drug must be given early in the course of the disease; (2) therapeutically effective levels must be maintained in the body throughout the treatment period; (3) treatment should continue for at least 2 days after remission of clinical signs; and (4) the causative bacterial agents must be sensitive to the drug.


Federal law restricts this drug to use by or on the order of a licensed veterinarian.


Primor should not be used in dogs showing marked liver parenchymal damage, blood dyscrasias, or in those with a history of sulfonamide hypersensitivity.


Not for human use. For use in dogs only. Keep out of reach of children.


Decreased water consumption and aciduria enhance the probability of the formation of sulfonamide crystals in the urine. Monitoring urine samples for crystal formation is recommended from animals with acid urine receiving the drug. As with any sulfonamide therapy, make certain dogs maintain adequate water intake. If dogs show no improvement within 2 or 3 days, reevaluate the diagnosis. Safety in breeding dogs has not been established.

Adverse Reactions:

Conditions reported following use of sulfonamides include polyarthritis, urticaria, facial swelling, fever, hemolytic anemia, polydypsia, polyuria, hepatitis, vomiting, anorexia, diarrhea, and neurologic disorders. In rare instances, neurologic signs including behavioral changes, ataxia, seizures, aggression, and hyperexcitability have been reported. Keratitis sicca, possibly due to prolonged use of sulfonamides, has been reported.

Individual animal hypersensitivity may result in local or generalized reactions. Anaphylactoid reactions, although rare, may also occur.

Antidote: Epinephrine for anaphylactoid reactions.


Store at controlled room temperature 15°-30°C (59°-86°F).

Toxicity and Safety:

Toxicity data for Primor indicate that the drug is safe when used at the recommended dosage.

Following oral administration of Primor to dogs at 27.5 mg/kg/day (12.5 mg/lb/day) for 8 weeks, no changes were noted in hematology, blood chemistry, urinalysis, gross pathology, and histopathology, except for elevated serum cholesterol, increased thyroid and liver weights, enlarged basophilic cells in the pituitary, and mild follicular thyroid hyperplasia. These changes are known to be associated with prolonged administration of sulfonamides to dogs and have been shown to be reversible.


Primor is a potentiated sulfa drug used in dogs for the treatment of skin and soft tissue infections (wounds and abscesses), and urinary tract infections caused by susceptible bacteria. Primor may also be used for other conditions not listed.Primor is a prescription medication FDA-approved for veterinary use in dogs. Primor is available as scored tablets in two strengths: Primor 240 which contains 200 mg sulfadimethoxine and 40 mg ormetoprim, and Primor 1200 which contains 1000 mg sulfadimethoxine and 200 mg ormetoprim. Primor is not for use in pets allergic to it or other sulfa drugs.
Tell your veterinarian if your pet is allergic to Primor or other sulfonamides (sulfa drugs). Tell your veterinarian if your pet has liver disease or blood dyscrasias, is dehydrated, or is pregnant or lactating. Also tell your veterinarian what other medication, including vitamins and supplements, that you are giving your pet while giving Primor.
The usual initial starting dose is 25 mg/lb on the first day of treatment followed by 12.5 mg/lb given once a day. Treatment should continue for 2 days after symptoms disappear. However, treatment should not exceed 21 consecutive days. Give Primor by mouth. It may be given with food. Leave plenty of water for your pet to drink. Always follow the dosage instructions provided by your veterinarian. Do not give Primor to any pet other than the pet for whom it was prescribed. If you do not understand the directions ask your pharmacist or veterinarian to explain them to you. Store Primor at room temperature in a tight, light-resistant container. Keep this medication away from children and pets.
Sulfa crystals may appear in your pet's urine. Your pet should be allowed to drink plenty of water while taking this medication. Other side effects that may occur include KCS or dry eye, anemia, fever, loss of appetite, vomiting or diarrhea, joint inflammation, kidney damage, or skin rash. Stop the medication and contact your veterinarian if any of the above symptoms occur. Other side effects may also occur. Talk to your veterinarian about any side effect that seems unusual or bothersome to your pet. If your pet experiences an allergic reaction, signs may include facial swelling, hives, scratching, and sudden onset of diarrhea, vomiting, shock, seizures, or coma. If these signs occur, contact your veterinarian immediately.
Give the missed dose as soon as you remember during the same day. However, if you don't remember until the next day, skip the dose you missed and give only the next regularly scheduled dose. Do not give a double dose of the medication.
Seek emergency veterinary medical treatment. Symptoms of overdose may include side effects listed below and may also include behavioral changes.
Antacids may decrease the effectiveness of sulfa drugs such as Primor. Give antacids 2-3 hours before or after giving a dose of Primor.
Before giving Primor, tell your veterinarian if your pet is being given methotrexate, warfarin, phenylbutazone, thiazide diuretics, aspirin, probenecid, or phenytoin.

Customers Who Bought Also Bought