WHITFIELDS OINTMENT

Indications

• Topical treatment of fungal infections
• Preservative in food and pharmaceutical products
• Treatment of hyperammonemia (as part of a combination therapy)

Dosage

Children: Refer to specific product guidelines and clinical protocols for pediatric dosing information.

Adults: Refer to specific product guidelines and clinical protocols for dosing information.

Mechanism of action

Benzoic acid exerts its antimicrobial effects primarily by disrupting the integrity of microbial cell membranes, leading to cell lysis. It can also inhibit certain metabolic pathways in bacteria, such as the conversion of pyruvate to acetyl-CoA, thereby limiting energy production in these organisms.

Pharmacodynamics

Benzoic acid demonstrates a concentration-dependent antibacterial and antifungal activity. The efficacy of benzoic acid is influenced by the pH of the environment; it is more effective in acidic conditions. The compound acts on a broad spectrum of microorganisms, including some bacteria and fungi, making it a useful preservative and therapeutic agent.

Pharmacokinetics

Benzoic acid is absorbed through the gastrointestinal tract when ingested and can be metabolized in the liver. It is primarily excreted in the urine as hippuric acid after conjugation with glycine. The half-life of benzoic acid varies but is generally around 1 to 2 hours. Its distribution in the body is rapid, with a volume of distribution that suggests extensive tissue binding.

Adverse effects

• Allergic reactions
• Skin irritation
• Nausea
• Vomiting
• Headache

Precautions

• Use with caution in individuals with known hypersensitivity to benzoates
• Monitor for signs of hypersensitivity reactions

Pregnancy

The safety of benzoic acid during pregnancy has not been established. Use only if the potential benefit justifies the potential risk to the fetus.

Breast-feeding

Benzoic acid is excreted in breast milk. Caution is advised when administered to nursing mothers.

Storage

Store in a cool, dry place, away from direct sunlight and moisture. Keep out of reach of children.

Formulations

• Topical creams
• Ointments
• Solutions

Indications

• Acne vulgaris
• Psoriasis
• Warts
• Seborrheic dermatitis
• Dandruff
• Hyperkeratosis

Dosage

Adults: For topical application, salicylic acid is typically applied once or twice daily, depending on the formulation and condition being treated. Specific dosing guidelines should be followed as per the BNF.

Mechanism of action

Salicylic acid exerts its effects by penetrating the skin and exfoliating the stratum corneum through keratolytic action, which helps in the dissolution of keratin and the removal of dead skin cells. This action facilitates the clearance of pores and can reduce acne lesions. Additionally, salicylic acid has anti-inflammatory properties that can help to decrease swelling and redness associated with various skin conditions. The compound is also known to inhibit the activity of enzymes involved in the synthesis of prostaglandins, which are mediators of inflammation.

Pharmacodynamics

The pharmacodynamics of salicylic acid involve its ability to enhance the turnover of skin cells and reduce the cohesiveness of keratinocytes in the stratum corneum. This leads to increased desquamation and a reduction in the formation of microcomedones in acne. Its anti-inflammatory effects are mediated through the inhibition of cyclooxygenase enzymes, leading to decreased production of pro-inflammatory mediators. This contributes to the reduction of inflammation and pain in affected areas.

Pharmacokinetics

Salicylic acid is absorbed percutaneously when applied topically, with systemic absorption increasing with higher concentrations and prolonged application. Once absorbed, it is metabolized predominantly in the liver to various conjugates, which are then excreted by the kidneys. The elimination half-life can vary based on the formulation and concentration used. For topical applications, significant first-pass metabolism may occur, limiting systemic exposure and reducing potential systemic side effects.

Pregnancy

Salicylic acid is classified as pregnancy category C. Its use should be avoided during pregnancy unless the potential benefits outweigh the risks.

Breast-feeding

Salicylic acid is excreted in breast milk, and caution is advised when using it during breastfeeding.

Storage

Store in a cool, dry place away from direct light.