Sulphacetamide

Usage

Sulphacetamide, an antibiotic belonging to the sulfonamide class, is primarily used to treat bacterial infections of the eye. It is effective against a broad spectrum of gram-positive and gram-negative bacteria. Its primary use is for the treatment of conjunctivitis, a common eye infection, and trachoma, a more serious eye infection that can lead to blindness. It can also be used for other superficial ocular infections. Sulphacetamide works by inhibiting bacterial growth by interfering with the synthesis of folic acid, a nutrient essential for bacterial multiplication.

Alternate Names

Sulphacetamide is also known as sulfacetamide sodium. Brand names include Bleph 10 and Sodium Sulamyd.

How It Works

Pharmacodynamics: Sulphacetamide exerts a bacteriostatic effect.

Pharmacokinetics:

• Mechanism of Action: Sulphacetamide acts as a competitive inhibitor of para-aminobenzoic acid (PABA). PABA is essential for bacterial synthesis of dihydrofolic acid, a key component in the production of nucleic acids. By blocking this pathway, sulphacetamide prevents bacterial growth and replication.

• Absorption: When applied topically to the eye, sulphacetamide penetrates ocular tissues and fluids, reaching therapeutic levels in the target site. Systemic absorption from the eye is minimal, especially when the conjunctiva is not inflamed.

• Metabolism: A small amount of sulphacetamide is metabolized to sulfanilamide.

• Elimination: Sulphacetamide, primarily in its unchanged form, is excreted via the kidneys with an elimination half-life of 7-13 hours.

Dosage

Standard Dosage

Adults:

• Solution: 1-2 drops in the affected eye(s) every 2-3 hours initially. The frequency can be reduced as the condition improves.
• Ointment: Apply a small amount (approximately a half-inch ribbon) into the affected eye(s) 3-4 times a day and at bedtime. As with the solution, the application frequency can be reduced with improvement.

Children:

• Children above 2 months: Similar dosing as adults.
• Infants below 2 months: Safety and efficacy not established.

Special Cases:

• Elderly Patients: No specific dosage adjustments are typically required.
• Patients with Renal Impairment: Caution is advised, and dose adjustment may be necessary.
• Patients with Hepatic Dysfunction: Caution is advised.
• Patients with Comorbid Conditions: Consider individual patient factors and adjust as needed.

Clinical Use Cases Dosage is generally the same as standard dosage across the listed clinical use cases, adjusting for individual response and severity of infection.

• Intubation
• Surgical Procedures
• Mechanical Ventilation
• Intensive Care Unit (ICU) Use
• Emergency Situations

Side Effects

Common Side Effects:

• Stinging or burning of the eye
• Eye irritation or redness
• Itching
• Swelling

Rare but Serious Side Effects:

• Stevens-Johnson syndrome
• Toxic epidermal necrolysis
• Severe allergic reactions
• Blood dyscrasias (agranulocytosis, aplastic anemia)
• Fulminant hepatic necrosis

Adverse Drug Reactions (ADR)

Severe allergic reactions and severe skin reactions.

Contraindications

• Hypersensitivity to sulphacetamide, sulfonamides, or any component of the formulation.
• Infants younger than 2 months of age (ophthalmic formulations).
• Kidney disease (for topical cream/lotion).

Drug Interactions

• Silver preparations are incompatible with sulphacetamide ophthalmic.
• PABA or procaine group of local anesthetics may antagonize the effects of sulphacetamide.
• CYP3A4 inhibitors may increase the risk of systemic side effects when used with topical corticosteroids containing sulfacetamide.
• Sulfacetamide can interact with some medications like hormonal contraceptives, cyclosporine, rifampin and warfarin.

Pregnancy and Breastfeeding

• Pregnancy: Sulfacetamide is a pregnancy Category C drug. It should be used during pregnancy only if the potential benefit outweighs the potential risk to the fetus. Avoid during the last month of pregnancy.

• Breastfeeding: It is not known if sulfacetamide is excreted in human milk. A decision should be made whether to discontinue breastfeeding or discontinue the drug, taking into account the importance of the drug to the mother.

Drug Profile Summary

• Mechanism of Action: Inhibits bacterial folic acid synthesis.
• Side Effects: Stinging, burning, itching, redness, swelling, rarely severe allergic reactions, skin reactions, and blood disorders.
• Contraindications: Hypersensitivity to sulfonamides, infants under 2 months (ophthalmic).
• Drug Interactions: Silver preparations, PABA-containing anesthetics, CYP3A4 inhibitors.
• Pregnancy & Breastfeeding: Category C; use with caution if benefits outweigh risks. Not recommended while breastfeeding.
• Dosage: Varies by formulation and indication. See detailed dosage section.
• Monitoring Parameters: Monitor for signs of improvement or worsening infection, allergic reaction, or other adverse events.

Popular Combinations

Sulfacetamide is sometimes combined with prednisolone acetate (a corticosteroid) to treat eye inflammation and infection concurrently.

Precautions

• Do not use if solution becomes discolored.
• Avoid contact of the dropper tip with any surface to prevent contamination.
• Wash hands before and after use.

FAQs (Frequently Asked Questions)

Q1: What is the recommended dosage for Sulphacetamide?

A: The dosage varies depending on the formulation and indication. See the detailed dosage section above.

Q2: What are the common side effects of Sulphacetamide?

A: Common side effects include stinging, burning, itching, redness, and swelling of the eye.

Q3: Is Sulphacetamide safe to use during pregnancy?

A: It is a Pregnancy Category C drug. Use only if the benefits outweigh the risks.

Q4: Can I use Sulphacetamide while breastfeeding?

A: Sulfacetamide’s safety during breastfeeding is unknown. Discuss with a doctor to weigh risks and benefits.

Q5: How does Sulphacetamide work?

A: It inhibits bacterial folic acid synthesis, thus preventing bacterial growth.

Q6: What infections does Sulphacetamide treat?

A: Primarily bacterial eye infections like conjunctivitis and trachoma.

Q7: Are there any drug interactions I should be aware of?

A: Yes, avoid concurrent use with silver preparations and PABA-containing anesthetics.

Q8: What should I do if I experience side effects?

A: Contact your doctor immediately, especially if side effects are severe or persistent.

Q9. What precautions should I take when administering Sulfacetamide ophthalmic?

A: Wash hands before and after application, avoid touching the tip of the container to the eye or any other surface, and discontinue use if the solution changes color.

Q10. How long does it typically take for Sulfacetamide to improve symptoms?

A: Most patients see improvement in conjunctivitis symptoms within 2-3 days.

Please note that this information is current as of February 17, 2025, and is subject to change. Always consult with a qualified medical professional for personalized advice.