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(for veterinary information only)
AVAILABLE AS
124 mg, 250 mg, 500 mg
TABLETS
AND
ORAL SUSPENSION
Sulfadimethoxine is an antibiotic of the sulfonamide class. As with other antibiotics, it is important that they inhibit or kill the infectious agent without injuring the host. In the case of the sulfas, the mechanism of action involves the essential nutrient known as Folic acid.
Folic acid is made from para-amino benzoic acid (PABA) through a step by step process involving two enzymes. The sulfa drug inhibits the first enzyme thus leading to the cell’s inability to reproduce. If the cell is a bacterial or parasite cell, this would be desirable. If the cell is a host cell, then we obviously would not want to interfere with the cell’s mechanisms. Fortunately, mammal enzymes are far less sensitive to the enzyme blockade than bacterial enzymes but what really protects the infected host from the blockade is the simple fact that mammals do not have to manufacture their own folic acid; they can eat it in their diet and do not have to depend on enzymes to manufacture it in any way.
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Gerhard Domagk in his laboratory
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We would be remiss not to mention the historical significance of this antibiotic class. The sulfa or “sulfonamide” class of antibiotics has earned a special place in history as the very first antibiotics ever developed. The first sulfa drug was synthesized in 1932 by a German scientist named Gerhard Domagk who was working for Bayer. He won the Nobel prize for Medicine and Physiology in 1939 for his work and numerous related sulfas were soon to follow. The sulfas saved numerous lives during World War II on both sides.
Sulfa drugs may have numerous uses but, in small animals, sulfadimethoxine is used almost exclusively for the treatment of intestinal parasites known as Coccidia. These parasites are single-celled organisms capable of causing intense diarrheas in their hosts.
Toxicity of the diuretics called “thiazides” may be enhanced by concurrent use of sulfa drugs.
This medication can precipitate in urine forming crystals or even stones. This is typically a problem with prolonged use or acidified urine.
Sulfa drugs have numerous potential side effects and though they may be rare, it is a good idea to become familiar with what to look for. The following are syndromes that can occur in certain individuals taking sulfa drugs. These syndromes represent “idiosynchratic” reactions which mean their occurance has nothing to do with the amount of drug given but instead represent an unpredictable individual’s sensitivity to any dose:
Joint inflammation
A broad inflammatory syndrome has been observed in some individuals sensitive to sulfas. This includes arthritis, fever, muscle soreness, and even kidney inflammation, and even inflammation in the eye. This syndrome has been formally studied and has been found to occur almost exclusively after a previous uneventful exposure to trimethoprim sulfa and occurs 8-20 days after therapy has started. The Doberman pinscher seems to be over-represented and complete recovery can be expected within one week of discontinuing the medication.
Skin rashes
Drug related skin reactions do not have characteristic appearances; in fact, they can have any appearance. They do, however, begin around the start of treatment with the offending drug and vanish with cessation of administration of the offending drug. Any drug of any kind can produce a drug reaction in the skin; trimethoprim sulfa is somewhat over-represented in cases of skin related drug eruptions.
Inability to produce adequate tears
Sulfa drugs of any kind are capable of disrupting tear function. Classically, this occurs after long term therapy
(i.e. weeks to months) of use but occasionally certain individuals suffer from dry eyes after only one dose of sulfa. In most cases, tear function resumes normally after the drug is discontinued but occasionally the effect is long term or permanent despite withdrawal of the drug.
Blood dyscrasias
Blood dyscrasias are abnormal blood cells or proportions of different blood cells. Blood dyscrasias might lead to immune dysfunction, bleeding tendency, or other problems depending on which blood cells are affected. With sulfas, loss of red blood cells, platelets, and white blood cells have been reported. This syndrome is typically part of the joint inflammation syndrome.
- It has been recommended that this medication not be used in patients with liver or kidney disease. In species other than dogs, sulfadimethoxine is removed from the body after it is “acetylated” in the liver and directly excreted by the liver. Patients with liver disease may not remove sulfadimethoxine properly from their bodies and may suffer toxic effects. In the dog, sulfadimethoxine is removed by the kidneys.
- Patients with known reactions against members of the sulfa class of antibiotics should not take this medication.
- Since inability to produce adequate tears (“Dry Eye”) is a possible side effect of sulfa drugs, it is prudent not to use them in patients that already have this condition independently.
- This medication is not considered safe in pregnancy.
Page last updated: 5/25/2011
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