Sulfadimethoxine (or sulphadimethoxine, trade names Di-Methox or Albon) is a long-lasting sulfonamide antimicrobial medication used in veterinary medicine. It is used to treat many infections, including respiratory, urinary tract, enteric, and soft tissue infections[3] and can be given as a standalone or combined with ormetoprim to broaden the target range.[2] Like all sulfamides, sulfadimethoxine inhibits bacterial synthesis of folic acid by acting as a competitive inhibitor against PABA. It is the most common drug prescribed to dogs who have coccidiosis.[4]
Like other sulfonamides, sulfadimethoxine is a dihydropteroate synthase inhibitor. Bacteria and some protozoa are unable to obtain folic acid from the environment, and must instead synthesize it by converting PABA (para-aminobenzoate) to dihydropteroate using the enzyme dihydropteroate synthase. Sulfonamides act as a competitive inhibitor; being structurally similar to PABA, they are able to bind to the enzyme's active site and prevent the synthesis of folic acid from progressing. Folic acid is necessary for these organisms to produce nucleic acids (i.e. DNA and RNA), which are required for cell division.[5] Thus, it has a microbiostatic effect rather than a microbiocidal one (it prevents pathogen growth rather than killing them), and has the strongest effect in the beginning stages of an infection, when the pathogen is rapidly dividing. Since it is microbiostatic, sulfadimethoxine still requires the animal to still be able to mount an immune response to kill the pathogen.[6][3]
With ormetoprim
Sulfadimethoxine can either be given alone (such as under the commercial name Albon) or in combination with ormetoprim to as a "potentiated sulfonamide" to increase antimicrobial activity.[2] Ormetoprim is a diaminopyridine, inhibiting dihydrofolate reductase, which is further along the pathway for synthesizing folic acid. Though the optimum ratio of sulfadimethoxine to ormetoprim has been found to be 20:1, it is sold pharmaceutically as a 5:1 mixture.[6]
Pharmacokinetics
Suspension and bottle of pills of sulfadimethoxine, sold under the trade name Albon.
Sulfadimethoxine, like all sulfonamides, diffuses easily when it is in its unionized, lipid-soluble form, and easily reaches many tissues. The relative amounts are determined by both its pKa and by the pH of each tissue. Therefore, levels tend to be higher in less acidic tissue and body fluids or in diseased tissues having high concentrations of leucocytes.[7][3][6] Its ability to bind to plasma proteins is very high, leading sulfadimethoxine to maintain higher blood levels than most other long-acting sulfonamides. Comparatively low doses can give rapid and sustained therapeutic blood levels.[3] Most animals for which sulfadimethoxine is marketed acetylate sulfadimethoxine in the liver to form acetylsulfadimethoxine, which is secreted in the bile. Dogs are the exception – since they are unable acetylate sulfonamides, they excrete sulfadimethoxine mostly unchanged in the urine (their inability to transform sulfadimethoxine also makes them more susceptible to negative side effects).[8][9][10]
Sulfadimethoxine has a relatively high solubility at the pH normally occurring in the kidneys, and is easily reabsorbed into the renal tubules, adding to its long half-life.[11][8] The use of sulfadimethoxine raises concerns that it will precipitate in the kidneys, leading to crystalluria. Though crystallization is not actually a common occurrence in veterinary medicine, it can be avoided entirely by adding a diaminopyrimidine such as ormetoprim.[11][6] Having the animal stay well-hydrated also is advised.[12]
Use & Dosage
Sulfadimethoxine is the only FDA-approved drug for treating intestinal coccidioisis in cats and dogs.[2] It is also used for:
It is also one of the only sulfonamides allowed for treating lactating dairy cattle (the others being sulfabromethazine and sulfathoxypyridazine).[6] The proper dosage of sulfadimethoxine depends on the animal species, the medical condition being treated, and the specific formulation of the medication. Using a tool like Sulfadimethoxine dosage calculator is important to determine the right dosage based on the animal's weight and species.[13][14][15]
↑ Stowe CM (1965). "Chapter 33: The Sulfonamides". In Jones LM (ed.). Veterinary Pharmacology and Therapeutics. Ames, Iowa: Iowa State University Press.
1 2 3 Plumb DC (2011). Plumb's Veterinary Drug Handbook (7thed.). Ames, Iowa: Wiley. pp.951, 954. ISBN9780470959640.
↑ Papich MG (2007). Saunders handbook of veterinary drugs (2nded.). St. Louis, Mo: Saunders/Elsevier. ISBN9781416028888.
Trimethoprim (TMP) is an antibiotic used mainly in the treatment of bladder infections. Other uses include for middle ear infections and travelers' diarrhea. With sulfamethoxazole or dapsone it may be used for Pneumocystis pneumonia in people with HIV/AIDS. It is taken orally.
4-Aminobenzoic acid (also known as para-aminobenzoic acid or PABA because the two functional groups are attached to the benzene ring across from one another in the para position) is an organic compound with the formula H2NC6H4CO2H. PABA is a white solid, although commercial samples can appear gray. It is slightly soluble in water. It consists of a benzene ring substituted with amino and carboxyl groups. The compound occurs extensively in the natural world.
Sulfonamide is a functional group that is the basis of several groups of drugs, which are called sulphonamides, sulfa drugs or sulpha drugs. The original antibacterial sulfonamides are synthetic (nonantibiotic) antimicrobial agents that contain the sulfonamide group. Some sulfonamides are also devoid of antibacterial activity, e.g., the anticonvulsant sultiame. The sulfonylureas and thiazide diuretics are newer drug groups based upon the antibacterial sulfonamides.
Acepromazine, acetopromazine, or acetylpromazine is a phenothiazine derivative antipsychotic drug. It was used in humans during the 1950s as an antipsychotic, but is now almost exclusively used on animals as a sedative and antiemetic. A closely related analogue, chlorpromazine, is still used in humans.
Sulfamethoxazole is an antibiotic. It is used for bacterial infections such as urinary tract infections, bronchitis, and prostatitis and is effective against both gram negative and positive bacteria such as Escherichia coli and Listeria monocytogenes.
An antimetabolite is a chemical that inhibits the use of a metabolite, which is another chemical that is part of normal metabolism. Such substances are often similar in structure to the metabolite that they interfere with, such as the antifolates that interfere with the use of folic acid; thus, competitive inhibition can occur, and the presence of antimetabolites can have toxic effects on cells, such as halting cell growth and cell division, so these compounds are used in chemotherapy for cancer.
Coccidiosis is a parasitic disease of the intestinal tract of animals caused by coccidian protozoa. The disease spreads from one animal to another by contact with infected feces or ingestion of infected tissue. Diarrhea, which may become bloody in severe cases, is the primary symptom. Most animals infected with coccidia are asymptomatic, but young or immunocompromised animals may suffer severe symptoms and death.
Moxidectin is an anthelmintic drug used in animals to prevent or control parasitic worms (helminths), such as heartworm and intestinal worms, in dogs, cats, horses, cattle, sheep and wombats. Moxidectin kills some of the most common internal and external parasites by selectively binding to a parasite's glutamate-gated chloride ion channels. These channels are vital to the function of invertebrate nerve and muscle cells; when moxidectin binds to the channels, it disrupts neurotransmission, resulting in paralysis and death of the parasite.
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Dihydropteroate is an important intermediate in folate biosynthesis. It is a pterin created from para-aminobenzoic acid (PABA) by the enzyme dihydropteroate synthase.
Dihydropteroate synthase (DHPS) is an enzyme classified under EC 2.5.1.15. It produces dihydropteroate in bacteria, but it is not expressed in most eukaryotes including humans. This makes it a useful target for sulfonamide antibiotics, which compete with the PABA precursor.
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