Ophthalmic Formulations: Sulfacetamide
Sulfacetamide (known as albucid) is available as eye drops and ointments. The drug penetrates ocular tissues and fluids exceptionally well. However, in cases of severe conjunctival inflammation, systemic absorption into the bloodstream can occur.
It is used in ophthalmology to treat conjunctivitis, blepharitis, and purulent corneal ulcers. The standard dosing regimen is 1–2 drops instilled 4 to 6 times daily.
Tolerability is generally good, but high concentrations can cause local irritation: burning, itching, grittiness, and lacrimation. In such cases, therapy is adjusted by switching to lower-concentration solutions.
Silver-Containing Agents
This group includes silver sulfadiazine and silver sulfathiazole. The presence of a silver atom fundamentally alters pharmacodynamics: upon dissociation, silver ions ($Ag^+$) are released, which bind to bacterial DNA. This provides a potent bactericidal effect.
The main distinguishing feature of these drugs is that their efficacy does not decrease in the presence of pus and tissue breakdown products. This is because the mechanism of action of silver ions does not depend on competition with para-aminobenzoic acid (PABA).
The spectrum of activity is broad and includes wound pathogens: staphylococci, Escherichia coli, Proteus, and Klebsiella. Of particular value is activity against Pseudomonas aeruginosa.
They are used topically as ointments for burn and wound infections, trophic ulcers, and pressure ulcers. Possible adverse effects include local allergic reactions, itching, and burning at the application site.
Combination Drugs for the Gastrointestinal Tract
This group includes sulfasalazine, salazopyridazine, and salazodimethoxine. Chemically, they are azo compounds linking a sulfonamide moiety and salicylic acid.
They are poorly absorbed in the small intestine, reaching the lower GI tract. In the colon, local microflora cause hydrolysis (cleavage) of the compound into two active components:
- 5-aminosalicylic acid (5-ASA) — exerts a potent anti-inflammatory effect.
- Sulfonamide component — provides a local antibacterial effect.
Main indications: ulcerative colitis, Crohn's disease, and as baseline therapy for rheumatoid arthritis.
Sulfasalazine Toxicity and Group Status
Sulfasalazine is administered orally (per os) and possesses a broad spectrum of toxicity. Allergic reactions, dyspepsia, and rectal burning may occur. Hematologic adverse effects include leukopenia and agranulocytosis. The central nervous system may react with ataxia, seizures, tinnitus, and hallucinations. Cases of photosensitization and interstitial pneumonitis have also been described.
In modern clinical practice, the use of sulfonamides is steadily declining. This is due to three factors:
- They are significantly inferior in antibacterial activity to modern antibiotics.
- They possess comparatively high toxicity.
- Microorganisms rapidly develop resistance to them.