Sulfamethoxazole Trimethoprim For Cats: Dosage Chart & Calculator

Sulfamethoxazole and Trimethoprim combination is a Broad-spectrum antibiotic used to treat bacterial and protozoal infections in cats.

The active ingredients Sulfamethoxazole work as a shield against the growth and development of bacteria, controlling Bacterial DNA synthesis By inhibiting the synthesis of folic acid. 

While Trimethoprim adds effectiveness against DNA replication, starving the bacteria of nucleotides. 

Sulfamethoxazole and Trimethoprim is not an FDA-approved veterinary medication. However, it is prescription medication by veterinarians around the world.

 Knowing about the safe dosage, benefits, potential side effects, and safe administration is essential for every feline owner to avoid toxicity and other health complications.

This article is a comprehensive guide about Sulfamethoxazole and Trimethoprim For Felines

Sulfamethoxazole Trimethoprim For Cats

Sulfamethoxazole Trimethoprim For Cats Dosage

The general  dose of  Sulfamethoxazole Trimethoprim for cats is 25-100mg/kg or 13-50mg/lbs every 24 hours or  12-50mg/kg or 7-25mg/lb twice daily every 12 hours. 

Note that the ideal dose of this antibiotic to treat the specific infection can be increased and decreased, and your veterinarian will better decide the recommended amount for your pet. 

For the safe dosage, dividing the tablet according to your pet’s body weight is suggested. 

How Sulphamethoxazole/Trimethoprim is Supplied for pets?

For the use of dogs and cats, Trimethoprim & Sulphamethoxazole Tablets are supplied in the below variants (Sulfamethoxazole+Trimethoprim)

  • 25mg/5mg Tablets
  • 100mg/20mg Tablets
  • 400mg/80mg Tablets
  • 800mg/160mg Tablets

Trimethoprim Sulfamethoxazole Dosage Chart For Cats

Cat body weight kg
(25-100 mg/kg
Weight in lbs  (13-50mg/lbs)Sulfamethoxazole Trimethoprim Dosage
1kg2 lbs25-100 mg
2 kg4 lbs50-200 mg
3 kg6 lbs75-300 mg
4 kg8 lbs100-400 mg
5 kg11 lbs125-500 mg
6 kg13 lbs150-600 mg
7 kg15 lbs175-700mg

Dosage Calculator

How Much 25mg/5mg Sulfamethoxazole Trimethoprim For Cats?

Kitten body weight kg25mg/5mg Sulfamethoxazole Trimethoprim Dosage
1kg1 tablet
2 kg2 tablets
3 kg3 tablets
4 kg4 tablets

25mg/5mg  Trimethoprim  Sulfamethoxazole tablets are usually prescribed for kittens.

How Much 100mg/20mg Sulfamethoxazole Trimethoprim For Cats?

Cat body weight kgSulfamethoxazole Trimethoprim 100mg/20mg Dosage
1kg1/4 tablet
2 kg1/2 tablet
3 kg1 tablet
4 kg1 tablet
5 kg1,1/2 tablets
6 kg1,1/2 tablets
7 kg2 Tablets

How Much Sulfamethoxazole Trimethoprim 400mg/80mg For Felines?

Cat body weight kg400mg/80mg Tablets Dosage
3 kg1/4 tablet
4 kg½  tablet
5 kg1/2 tablets
6 kg1/2 tablets
7 kg1 Tablets

How much 800mg/160mg Sulfamethoxazole Trimethoprim For Felines?

Cat body weight 800mg/160mg Tablets Dosage
4 kg1/4  tablet
5 kg1/4 tablet
6 kg1/3 tablets
7 kg1/2 Tablets
8 kg & Above1 Tablet

Uses of Sulfamethoxazole and Trimethoprim for Felines

Sulfamethoxazole and Trimethoprim can be used to treat various infections in felines. Veterinarians often prescribe antibiotics to treat:

Possible side effects of Sulfamethoxazole and Trimethoprim

Administrating the Sulfamethoxazole Trimethoprim in a safe dose with the vet prescription is safe for use in pets. However, As with other medications, Sulfamethoxazole and Trimethoprim also have minor to severe side effects. 

Some of the most reported adverse effects of Sulfamethoxazole and Trimethoprim in cats are:

Minor Side effects:

  • Increased thirst and urination
  • Pale gums
  • Tiredness
  • Fever
  • Loss of appetite
  • Facial swelling
  • Vomiting & Diarrhea

Severe Side Effects:

Which Cats should not take Trimethoprim and Sulfamethoxazole?

Use of Trimethoprim and Sulfamethoxazole is not safe for all cats and dogs. Some pets should not take the medication without a professional veterinarian’s prescription.

Make sure to inform your vet earlier if your kitty falls in any of the below categories. 

  1. Felines Allergic to  sulfonamides
  2. Pregnant  and lactating pets
  3. Pets with known hypersensitivities
  4. Having kidneys or liver illnesses
  5. Blood cell problems
  6. Dehydrated pets 
  7. Having or risk for urinary stones

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Which drugs should not be given parallel with Trimethoprim and Sulfamethoxazole?

Trimethoprim and sulfamethoxazole may interact with certain medications Include:

Tricyclic antidepressants, anticoagulants, oral hypoglycemic agents, salicylates, and pyrimethamine, methotrexate, antacids, phenylbutazone, cyclosporine, phenytoin, thiazide diuretics, methotrexate, warfarin, potassium supplements and potassium-sparing Diuretics drugs.

Do not give the antibiotic parallel with these groups of drugs, and inform your vet if your pet is on such medication. 

How to Give sulfamethoxazole/trimethoprim?

Use hand gloves before giving the medication to your pet. If you are allergic to sulfa compounds, don’t give it by yourself, administrate it by another family member. 

Ensure to administrate the safe dose of the tablet, suspension, or injectable form. Overdosing is toxic for pets and can be fatal. Never give two doses at once

Sulfamethoxazole/trimethoprim tablets and oral suspension can be given with or without food. To avoid gastrointestinal upset, mix the medication with your pet food. 

If you are using the oral suspension, make sure to shake well before use.

Keep your pet well hydrated during the treatment period. Dehydration while using sulfamethoxazole/trimethoprim can increase the risk of kidney and liver illnesses. 

If you are giving the sulfamethoxazole/trimethoprim twice a day, Make sure to keep at least a 6-7 hours gap between the doses. If you miss a dose, then follow the instructions.

If there is a 6-7 hours gap between the doses, administer the missing dose and then continue the regular schedule. However, if there is less than a 6-hour gap, then give the missed dose and skip the next regular dose and then continue the dosage according to your schedule. 

If you are giving the antibiotic on a daily schedule, make sure to keep a gap of at least 18-20 hours.

If you observe any side effects of the medication in your cat, stop giving the medicine and contact your veterinarian immediately. 

How much time does sulfamethoxazole/trimethoprim take to start work?

Usually, sulfamethoxazole/trimethoprim starts its effects about 2-3 hours after administration. However, the treatment period may take about 10 to 20 days. 

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