Acids and Alkalis

General Pharmacodynamic Effects

The antimicrobial activity of acids and alkalis is based on their ability to shift the hydrogen ion index at the site of application. In addition to directly destroying bacteria and fungi, these substances have marked effects on host tissues.

Alkaline compounds interact with living tissues in a specific manner. When applied to the skin or mucous membranes, alkalis react chemically with tissue proteins to form so-called albuminates, which possess a loose, soft structure (unlike the compounds formed by acids).

Due to this property, alkaline solutions effectively:

• Soften the epidermis;
• Dissolve viscous mucus, mucin, and inflammatory exudate accumulations;
• Reduce local acidosis via pH shifts and markedly decrease tissue edema;
• Promote mechanical washing and removal of pathogenic fungal mycelia.

Using weak alkaline solutions causes mild tissue irritation, leading to improved trophic support (nutrition).

Acid Preparations

In modern medical practice, two acid preparations with proven antiseptic activity are most commonly used:

1. Boric acid. This drug features a dual spectrum of action: it exerts both antibacterial and antifungal (fungistatic) effects. The choice of dosage form depends on the indication. Aqueous solutions are traditionally used for eye washing in conjunctivitis and for treating affected areas in skin dermatitis. Alcoholic solutions are a classic treatment for acute and chronic otitis media. Additionally, boric acid is an important component of well-known combination drugs such as Castellani paint (Fukorcin) and Boromenthol.

1. Salicylic acid. This agent is notable for a wide variety of dosage forms: ointments, pastes, powders, and alcoholic solutions are available. Its pharmacodynamics include antiseptic, irritant, and counter-irritant effects. Of particular note is its keratolytic action—the ability to soften and cause shedding of the stratum corneum of the epidermis, which is pronounced exclusively when the drug is used in high concentrations. The main indications for use include infected skin lesions, seborrhea, hyperhidrosis (excessive foot sweating), and corn removal. It is part of many combination products: corn liquids, Salipod adhesive plaster, Lassar's paste, Galmanin powder, and Diprosalic ointment.

Alkaline Preparations

The alkaline group is represented by several compounds widely used for topical treatment, rinses, and specific neutralization:

• Sodium bicarbonate (Sodium bicarbonate). Acts as a weak antiseptic. Used exclusively externally via washes and inhalations. Main indications include inflammatory processes of mucous membranes (rhinitis, stomatitis, conjunctivitis, pharyngitis/tonsillitis). The solution is also indispensable for the rapid neutralization of damaging agents (acids or toxic substances) upon contact with mucous membranes.
• Sodium tetraborate (Sodium tetraborate). Exhibits a pronounced bacteriostatic type of action. Its key feature is high specific activity against yeast-like fungi of the genus Candida. The drug effectively removes mycelium, disrupts fungal adhesion to the mucous membrane, and inhibits further reproduction. It is prescribed as rinses and lubricants for candidiasis of various localizations (oral cavity, pharynx, upper respiratory tract, urogenital tract), as well as for treating diaper dermatitis and pressure ulcers.
• Ammonia (Ammonia). Its mechanism stands out within this group: it causes protein coagulation, providing a potent bactericidal effect. Ammonia's pharmacodynamics combine antiseptic action with a strong irritant effect due to stimulation of sensory nerve endings. Used as liniments and lotions. Indicated for myalgia and neuralgia (as a counter-irritant), as well as for neutralizing acidic toxins from insect and snake bites.
• Calcium hydroxide (Calcium hydroxide). Chemically a strong base. It exerts a pronounced antiseptic effect and effectively suppresses inflammatory processes in the dental pulp. The drug is of immense dental significance: it is used for root canal disinfection and actively stimulates the regeneration and mineralization of dental tissues.