Side effects of sulfonamides

Allergic manifestations and dermatotoxicity

When prescribing sulfonamides, a physician must keep in mind the high risk of allergic reactions. The clinical picture of hypersensitivity can range from mild forms to conditions requiring discontinuation of therapy.

Basic manifestations include elevated body temperature (drug fever), intense skin pruritus, and the appearance of various rashes on the skin.

A separate and highly specific side effect is photosensitization. This phenomenon consists of an abnormal increase in the patient's skin sensitivity to ultraviolet radiation. During course administration of the drugs, even brief exposure to direct sunlight can provoke pronounced skin reactions. Patients undergoing therapy are strongly advised to avoid sun exposure to prevent phototoxic damage.

Organotoxicity and systemic disorders

Sulfonamides exert systemic effects on the body, which can be accompanied by toxic damage to several vital systems simultaneously.

1. Gastrointestinal tract: Patients frequently exhibit dyspeptic disorders. Impairments in normal digestion can reduce treatment adherence and require symptomatic correction.
2. Liver: The drugs possess proven hepatotoxicity. Toxic effects on hepatocytes dictate the need for cautious use in individuals with pre-existing pathologies of the hepatobiliary system.
3. Bone marrow and hematopoiesis: Hematotoxicity manifests as the suppression of various hematopoietic cell lines. In a clinical blood test, this may be reflected as:
4. Anemia (decreased red blood cell count);
5. Leukopenia (drop in white blood cell count);
6. Thrombocytopenia (decreased platelet count).

Renal damage: mechanism and prevention of crystalluria

The nephrotoxicity of sulfonamides is most often realized through the mechanism of crystalluria — the formation of insoluble crystals in the lumen of the urinary tract.

Condition of occurrence: A key risk factor is an acidic urine reaction (low pH level). It is precisely in an acidic environment that sulfonamide molecules lose their solubility. Instead of being freely excreted in the urine, they precipitate out. The resulting microscopic crystals can mechanically injure the mucous membrane of the renal tubules and ureters.

Prevention: To avoid this complication, it is necessary to artificially alter the urine reaction. Patients are prescribed abundant alkaline drinks. The use of alkaline mineral water or a weak solution of regular baking soda leads to the alkalinization of urine. In an alkaline environment, the drugs remain in a dissolved state and safely leave the body.

Pediatric practice: risk of kernicterus

The use of sulfonamides in neonatology (in newborn infants) is associated with the risk of developing a fatal complication — kernicterus, or nuclear jaundice.

Pathogenesis of the complication: In human blood, bilirubin is transported in a bound form with a protein — serum albumin. Sulfonamides have a high affinity for this protein and begin to compete with bilirubin for binding sites. As a result, the drug substance aggressively displaces bilirubin from the protein complex. This leads to a sharp increase in the fraction of free (unbound) toxic bilirubin in the infant's blood plasma.

Consequences: Free bilirubin easily crosses the blood-brain barrier of the newborn. Accumulating in the brain structures, it causes severe toxic damage to the central nervous system.

Clinical conclusion: Due to the threat of irreversible brain damage, sulfonamides are strictly contraindicated for use in newborns.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Mechanisms of development of drug-induced photosensitization
• Pathogenesis of hepatotoxicity of antibacterial drugs
• Competitive antagonism for binding to plasma proteins
• Features of blood-brain barrier permeability in newborns
• Influence of urine pH on pharmacokinetics and drug excretion

Other topics in the section "Antibacterial Chemotherapeutic Agents"

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