What is meant by sulfa drugs?

Posted on  November 12, 2020, Edited by Jason, Category  

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  1. What are sulfa drugs?
  2. Adverse reactions
  3. Classification
  4. Clinical application
  5. Notes
  6. Conclusion

What are sulfa drugs?

Sulfonamides are synthetic antibacterial drugs that have been used clinically for nearly 50 years. Sulfa drugs have the advantages of broad antibacterial spectrum, stable properties, easy use, and no food consumption during production. Especially after the discovery of the antibacterial synergist-trimethoprim (TMP), the combined application with sulfonamides can enhance its antibacterial effect and expand the treatment range. Therefore, although numerous antibiotics have come out, sulfa drugs are still important chemotherapy drugs.

If you eat dairy products, Ballya can also perform a sulfonamides test to tell you if there are sulfonamides residues in them.

what are sulfa drugs
what are sulfa drugs

Adverse reactions

  1. Improper use of sulfa drugs may cause allergic reactions, hemoglobinuria, anemia and other adverse reactions in pigs, and even endanger health. Therefore, pig farmers should pay great attention to sulfa drugs to avoid adverse reactions.
  2. Sulfonamides are prone to drug resistance. The metabolite in the liver, acetyl sulfonamide, has low solubility, and easily crystallizes in the urine, causing renal toxicity. Therefore, the dosage and time should be strictly controlled when taking the drug, and sodium bicarbonate and more water should be taken at the same time.


1. Sulfonamides that are easily absorbed from the intestine are used for systemic infections, such as sepsis, urinary tract infection, typhoid fever, osteomyelitis, etc., and are divided into short-acting, medium-acting and long-acting types according to the length of action of the drug.

  • Short-acting sulfonamides: fast absorption in the intestines, fast excretion, half-life of 5-6 hours, 4 times a day, such as sulfamethazine (SM2), sulfisoxazole (SIZ).
  • Intermediate-acting sulfonamides: The half-life is 10 to 24 hours, and it is taken twice a day, such as sulfadiazine (SD) and sulfamethoxazole (SMZ).
  • Long-acting sulfonamides: The half-life is more than 24 hours, such as sulfamethoxine (SMD), sulfadimethoxine (SDM), etc.

a. Sulfamethazine

The medicine is white crystalline powder, slightly soluble in water. It should be protected from light and air. After oral administration, absorption is fast and excretion is slow. The first intravenous injection of 0.10 g/kg body weight for dairy cows, cattle, and calves, and then 0.05 g/kg body weight per day for oral administration for 2 days, the effective blood concentration can be maintained for 72 hours. Horses and pigs are taken orally at 0.10 g/kg body weight, and the effective blood concentration can be maintained for 24 hours. Horses, cattle, sheep, pigs are 0.10 g/kg body weight, taken orally, once a day.

b. Sulfaethoxazine

This medicine is white or slightly yellow crystalline powder, slightly soluble in water, and should be protected from light and air. The drug is quickly absorbed after oral administration, and the half-life period after intravenous injection is 468 minutes for pigs, 11 hours for sheep and 10 hours for cattle. It is 0.055 g/kg body weight every time for cattle and sheep, and 0.130 g/kg body weight every time for pigs, taken orally, once a day.

2. Sulfonamides that are difficult to absorb in the intestine can maintain a high drug concentration in the intestine. It is mainly used for intestinal infections such as bacillary dysentery, enteritis, etc., such as phthalosulfathiazole (PST).

a. Sulfamidine

This medicine is white needle-like crystalline powder, slightly soluble in water, and should be stored out of air and light. Oral administration is less absorbed and can maintain a higher concentration in the intestines, so it is suitable for enteritis, diarrhea and other intestinal bacterial infections. However, it should be noted that the intestinal absorption rate of newborn animals is higher than that of young animals.

When drugs are administered to animals suffering from intestinal obstruction or severe dehydration, or when the dosage of adult animals is too large, kidney damage may occur due to excessive absorption. In addition, since adult ruminants have a lot of gastrointestinal contents, the concentration of the drug after oral administration will be diluted to reduce the efficacy, so it is now rarely used. All kinds of livestock and poultry 0.1~0.2 g/kg body weight every time, oral administration, 2 times/day.

b. Phthalosulfacetamide

The medicine is white or milky white crystalline powder, which is extremely difficult to dissolve in water. It is not easy to be absorbed when taken orally, and it gradually decomposes in the intestine, releasing sulfacetamide and showing antibacterial effect, which is more effective against Shigella bacteria. It is mainly used for mycosis, enteritis and prevention of bacterial infections before and after surgery. For foals, calves, lambs, piglets, rabbits, and poultry, the weight should be 0.1~0.3g/kg body weight, divided into 2~3 times orally.

c. Phthalosulfathiazole

This medicine is a white or slightly yellow crystalline powder, insoluble in water, and should be stored in a sealed and sealed form. After oral administration, the drug is more difficult to be absorbed than thiamine, and gradually releases sulfathiazole in the intestines, showing a bacteriostatic effect. The drug has less side effects and good curative effect, and is a good intestinal sulfonamide drug for preventing infection before and after intestinal surgery. For foals, calves, piglets, lambs, rabbits, and poultry, the weight is 0.1~0.3g/kg body weight, and it is taken orally in 3~4 times.

d. Hydroxyquinophthalein Sulfathiazole

The medicine is a light yellow crystalline powder, slightly soluble in water, and should be protected from air and light. This medicine is a compound salt of phthalosulfathiazole and 8-hydroxyquinoline. Its function and main purpose are the same as those of phthalosulfathiazole, and it also has the effect of treating amoebic dysentery. All kinds of livestock and poultry are taken orally in 2 to 3 times a day at 0.1 to 0.3 g/kg body weight.

e. Sulfamethoxazine

The drug is white or slightly yellow crystalline powder, insoluble in water, and difficult to be absorbed when taken orally. Sulfamethoxine is gradually precipitated in the intestinal tract and exhibits intestinal antibacterial effect. It can be used to prevent bacterial infections before and after gastrointestinal infections of various domestic animals or intestinal surgery. All kinds of livestock 0.1~0.3 g/kg body weight every time, oral administration, once a day.

3. Topical sulfa drugs are mainly used for burn infections, purulent wound infections, eye diseases, etc., such as sulfacetamide (SA), sulfadiazine silver salt (SD-Ag), methanesulfonate (SML).

a. Sulfa

The medicine is white or light yellow crystalline granule or powder, slightly soluble in water, and is extremely soluble in boiling water or boiling alcohol. The drug has the effect of inhibiting the growth and reproduction of bacteria, but it is rarely taken orally due to its high toxicity and poor efficacy. It is mainly used as external medicine for local infection.

b. Silver Sulfadiazine

The medicine is a white or nearly white crystalline powder, which is hard to dissolve in water. It should be protected from light and kept in a cool place. The drug has the same antibacterial spectrum as sulfadiazine, but has a powerful antibacterial effect on Pseudomonas aeruginosa. It has the effects of controlling infection, promoting dryness of the wound and accelerating healing. It is clinically suitable for wound infections, especially caused by Pseudomonas aeruginosa and second and third degree burns or scalds. After medication, there will be no adverse reactions such as electrolyte disturbance or metabolic acidosis, and there is no pollution to the tissues. Wounds treated with this medicine can be safely skin grafted.

c. Sodium Sulfacetamide

The agent is white crystalline powder, easily soluble in water. The medicament has a high solubility in water, and the solution is nearly neutral and has little irritation to the mucous membrane. Clinically, it is mainly used for eye infections, such as conjunctivitis and corneal purulent ulcers. 10%~30% of this medicine is eye drops or ointment for topical application.

d. Sulfamirone Acetate

The medicament is white or light yellow crystal or crystalline powder with acetic acid odor, and its aqueous solution is weakly acidic, easy to dissolve in water. The drug has a broad antibacterial spectrum and is effective against most gram-positive and gram-negative bacteria. Its characteristic is that it has a strong inhibitory or killing effect on Pseudomonas aeruginosa.

Its antibacterial effect is not affected by para-aminobenzoic acid, and it also has a therapeutic effect on wound infections with suppuration and necrotic tissue, and can penetrate the burning eschar, and it can also promote the growth and healing of the burn wound. Clinically, it can be used for the treatment of burn infection, surgical operation, traumatic local inflammation and Pseudomonas aeruginosa infection.

Topical application may cause pain or burning feeling, and sometimes may cause allergic reactions. Because the drug is quickly inactivated in the blood, it can only be used locally, not suitable for oral administration or injection.

Clinical application

It is simply summarized as "three infections and three inflammations", namely: respiratory tract, digestive tract, urinary tract infection; mastitis, metritis and peritonitis. In addition, sulfa drugs have a good therapeutic effect on toxoplasmosis and coccidiosis.

5 principles of using sulfa drugs:

  1. Double the amount for the first time so it can achieve the purpose of rapid bacteriostasis, and then use in the normal amount. After the symptoms disappear, give the minimum amount 2 to 3 times to maintain the efficacy of the medicine for a long time and prevent the rebound of bacteria.
  2. Pay attention to the compatibility taboo. Sulfonamides, especially compound synergistic sulfa preparations, cannot be compatible with penicillins, sodium bicarbonate, calcium chloride, vitamin C, vitamin B1, compound sodium chloride solution, etc., and must be used alone.
  3. Do not use it in large quantities for a long time. Although sulfa drugs have a good effect on bacteria such as Streptococcus suis, the bacteria will soon develop resistance after a period of time, causing all sulfa drugs to fail. At this time, other antibacterial drugs should be replaced quickly.
  4. Ensure adequate drinking water. Drinking more water for pigs can maintain high urine flow and prevent drug crystallization. For pigs who have been taking sulfa drugs for more than one week, they can take sodium bicarbonate alkalization solution if necessary.
  5. The drug must be stopped on time. In order to ensure the quality and safety of animal products, it is necessary to stop the drug on time before the pig is slaughtered in accordance with the provisions of the national and professional standards for veterinary drugs.


1. Single use

Single use can only inhibit bacteria but not sterilize, and bacteria are prone to cross-resistance to various sulfa drugs. (That is: bacteria develop resistance to a sulfa drug, and it has also acquired resistance to other sulfa drugs), so sulfa drugs are not recommended for use as health care drugs. In addition, once the sulfa drugs lose their efficacy, other antibacterial drugs should be replaced in time.

2. High cost

As mentioned earlier, although the price of sulfa drugs is relatively low, there is no effect if the dose is too small. Under normal circumstances, the dosage will be increased, which is bound to increase the cost of medicine. If the effect is not good and the condition is delayed, the loss will be even greater.

3. sulfa side effects

Excessive dosage or long-term use can easily cause acute or chronic poisoning of poultry. The chicks are acutely poisoned and will die in large numbers. Laying hens are chronically poisoned, the egg breakage rate increases, the number of soft-skinned eggs increases, and the egg production decreases significantly. In addition, unreasonable use of sulfa drugs will accumulate in the kidneys and cause kidney damage.

However, sulfa drugs are clinically widely used in the prevention and treatment of poultry colibacillosis, salmonellosis, coccidiosis, etc., and are the drugs of choice for infectious rhinitis and leukocytosis (white crown disease).


Sulfa drugs are widely used in aquaculture because of their unique advantages. However, the effect of sulfa drugs is closely related to the technique of use, and sulfa drugs, like other antibiotics, have certain side effects. We need to pay attention to the ecological and effective use of sulfa drugs in the production and application process.


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