Pharmacokinetics and mechanism of action
The main feature of this group is that the drugs are practically not absorbed in the gastrointestinal tract. Due to this, the medicinal substances create high concentrations directly in the intestinal lumen, acting on the pathogenic microorganisms localized there.
Main indications for use
These pharmacological agents are prescribed in the following clinical situations:
- Intestinal infections, including shigellosis, dysentery, enterocolitis, and gastroenteritis.
- Prevention of purulent complications during surgical interventions on the intestine.
Special pharmacology of the drugs
This group includes specific medicinal products with their own features of activation and use:
- Phthalylsulfathiazole: undergoes chemical alteration in the small intestine — phthalic acid is cleaved off, the amino group is released, after which the active substance is formed (sulfathiazole or norsulfazole). It is used 4–6 times a day, characterized by low toxicity and virtually no side effects.
- Sulfaguanidine: completely analogous to phthalylsulfathiazole in its mechanism and pharmacological action.
Combination and concomitant therapy
Since infectious agents can be located not only in the lumen but also in the intestinal wall, and can also cause resistance, monotherapy may be insufficient.
- Combinations: To increase treatment efficacy, it is advisable to combine intestinal forms with readily absorbed sulfonamides (such as, for example, sulphaethidole or sulphadimidine).
- Concomitant support: B vitamins (thiamine, riboflavin, nicotinic acid) must be prescribed. This is necessary because sulfonamides suppress the normal microflora — Escherichia coli, which normally is responsible for the synthesis of these vitamins in the human body.
Briefly: answers to topical questions
Which drugs belong to the group of intestinal sulfonamides?
The group of intestinal sulfonamides includes drugs poorly absorbed in the gastrointestinal tract that create high concentrations in the intestinal lumen. These include:
- Phthalylsulfathiazole — in the small intestine, it cleaves off phthalic acid, releases the amino group, resulting in the formation of an active substance (sulfathiazole or norsulfazole).
- Sulfaguanidine — analogous to phthalylsulfathiazole in mechanism and action.
What is the mechanism of the antibacterial action of sulfonamides at the cellular level?
The mechanism of the antibacterial action of sulfonamides consists in the competitive inhibition of the enzyme dihydropteroate synthase and the disruption of intracellular bacterial metabolism. Due to structural similarity with para-aminobenzoic acid (PABA), the drugs act as its competitive antagonists. They block the earliest stage of synthesis — the conversion of PABA into dihydropteroic acid and then into dihydrofolic acid. This prevents the formation of active forms of folic acid, which are necessary for the bacterial cell to synthesize nucleotides and subsequently multiply.
What is the spectrum of antibacterial action of intestinal sulfonamides?
The spectrum of use of intestinal sulfonamides includes intestinal infections: shigellosis, dysentery, enterocolitis, and gastroenteritis. Since pathogens can be localized not only in the lumen but also in the intestinal wall, and resistance may develop, to increase efficacy, it is advisable to combine the drugs with well-absorbed sulfonamides, for example, sulfasomidine or sulfadimidine.
What side effects and complications can occur with prolonged use of intestinal sulfonamides?
Phthalylsulfathiazole has low toxicity, and its side effects are practically absent. With prolonged use of sulfonamides, a change in the composition of the normal intestinal flora (dysbiosis) and the development of hypovitaminosis are possible due to the suppression of Escherichia coli, which participates in the synthesis of B vitamins: thiamine, riboflavin, and nicotinic acid. Therefore, when using sulfonamides, B vitamins are mandatory prescribed.
Class and exam questions
Why do intestinal sulfonamides create high concentrations specifically in the intestinal lumen?
Because these drugs have the property of being practically unabsorbed in the gastrointestinal tract.
Why are B vitamins mandatory prescribed during treatment with intestinal sulfonamides?
The drugs suppress Escherichia coli, which normally is responsible for the synthesis of B vitamins in the body, therefore their additional intake is required.
How is phthalylsulfathiazole activated in the body?
In the small intestine, phthalic acid is cleaved off from it, the amino group is released, and the active substance — sulfathiazole (norsulfazole) — is formed.
What else to study on this topic
- Mechanism of activation of phthalylsulfathiazole at the molecular level
- Schemes for combining intestinal sulfonamides with systemic drugs
- The role of Escherichia coli in the synthesis of B vitamins
- Prevention of surgical complications on the intestine using sulfonamides
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