Sulfadimethoxine + Ormetoprim

What is sulfadimethoxine + ormetoprim?

Sulfadimethoxine + ormetoprim (brand name Primor®) is a combination antibiotic used to treat bacterial skin and soft tissue infections in dogs. 

It is used off label (extra label) to treat other bacterial infections in dogs and in other species. Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada. In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.

How do I give my pet sulfadimethoxine + ormetoprim?

• Sulfadimethoxine + ormetoprim comes in tablet form. Tablets may be compounded into liquid form.
• Tablets and compounded liquids are given orally (by mouth). 
• This medication may be given with or without food. 
• If your animal vomits or acts sick after receiving the drug on an empty stomach, try giving the next dose with food or a small treat. If vomiting continues, contact your veterinarian. 
• Liquid medications must be measured carefully. Contact your veterinarian if you have trouble measuring or giving the medication.
• Give this medication to your pet for the entire time prescribed by your veterinarian, even if it appears that your pet is feeling better.

This medication should take effect within 1 to 2 hours, though effects may not be noticed outwardly right away.

What if I miss giving my pet the medication?

If you miss a dose, give it as soon as you remember, and then wait the recommended time as prescribed by your veterinarian for the next dose. Do not give the pet two doses at once.

Are there any potential side effects from sulfadimethoxine + ormetoprim?

Sulfadimethoxine + ormetoprim may cause the following side effects:

• Decreased appetite
• Diarrhea
• Vomiting

The following reactions are rare, but if they occur, contact your veterinarian immediately:

• An allergic reaction such as irregular breathing, rash, fever, puffiness and swelling around the face
• Yellowing of the eyes, gums, skin (jaundice)
• Red eyes, eye rubbing, increased blinking (signs of dry eye)

Drug sensitivities can develop over time with repeated exposure. Your pet may have no reaction after the first few doses, but may develop a sensitivity later. It is important to watch for signs of an allergic reaction over the entire course of treatment.

Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This medication is short-acting, meaning that effects will last less than 24 hours, though effects may last longer in pets with kidney or liver disease.

Are there any risk factors for this medication?

DO NOT USE in animals who:

• Are allergic to any component of the medication or who are allergic to similar drugs (i.e., other sulfa drugs)
• Have severe liver disease
• Have blood cell problems
• Are dehydrated

USE WITH CAUTION in:

• Pets who have kidney, liver, and/or thyroid disease
• Pets who are old, weak, frail
• Pets who have kidney or urinary stones
• Doberman pinschers

Are there any drug interactions I should be aware of?

Certain medications should be USED WITH CAUTION when given with sulfadimethoxine + ormetoprim, including: 

• Amantadine
• Anesthetic agents (e.g., procaine, lidocaine)
• Antacids
• Azathioprine, cyclosporine
• Blood pressure medications (e.g., telmisartan, benazepril)
• Digoxin
• Diuretics (e.g., furosemide)
• Oral hypoglycemia agents (e.g., glipizide, metformin)
• Methotrexate

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any new treatment.

Is any monitoring needed with this medication?

• Your veterinarian may assess baseline blood work (e.g., complete blood count, biochemistry, thyroid function) and/or Schirmer tear test function before starting this medication and periodically throughout treatment.
• Your veterinarian will schedule follow-up visits for monitoring. In this case, follow your veterinarian’s directions.
• At home, monitor for any abnormal changes. If any occur, discontinue the medication and contact your veterinarian.

How do I store sulfadimethoxine + ormetoprim?

• Store at room temperature of 15°C-30°C (59°F-86°F) in a tight container, protected from light.
• Follow storage and expiration recommendations for specially compounded formulas.
• Keep medication out of reach of children and pets.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Adverse effects should be reported to the FDA or Health Canada.