Boric Acid (Monograph)

Drug class: Astringents, Anti-infective

Medically reviewed by Drugs.com on May 10, 2024. Written by ASHP.

Introduction

Boric acid is a weak topical anti-infective agent.

Uses for Boric Acid

Boric acid is used topically as a skin protectant for relief of discomfort of chapped skin, chafed skin, diaper rash, dry skin, abrasions, sunburn, windburn, insect bites, or other skin irritations and has been used topically for the treatment of superficial fungal infections; however, the drug is generally considered as lacking substantial evidence of efficacy for these uses.

Boric Acid Dosage and Administration

As a skin protectant for the relief of discomfort associated with various skin conditions, 5% boric acid ointment is applied topically to the affected area 3 or 4 times daily. When used for self-medication in the treatment of superficial fungal infections, a thin layer of 0.5–5% boric acid ointment may be applied topically to the affected area twice daily in the morning and at night or as directed. Boric acid ointment should not be used for self-medication of athlete’s foot or ringworm for longer than 4 weeks or of jock itch for longer than 2 weeks. If the condition persists or recurs, a physician or pharmacist should be consulted.

Cautions for Boric Acid

Although topical preparations of boric acid containing a concentration of 5% or less pose no great hazard when applied to intact skin, severe poisonings and fatalities have occurred following topical application of the drug, usually when preparations (e.g., powder, ointment, solution) containing high concentrations were applied repeatedly and/or in large amounts to wounds; to burned, abraded, denuded, or macerated skin; or to large areas of skin. (See Acute Toxicity.) When a 10% ointment was applied topically to extensively denuded areas in one study, up to 2 g of boric acid was excreted in urine within 24 hours following application. The risk of systemic toxicity from topical application of boric acid depends on the concentration used (increased with high concentrations), age of the patient (infants and children appear to be more susceptible than adults to borate toxicity), skin condition (increased with abraded, denuded, or macerated skin), and duration of exposure (increased with longer exposure). Acute poisoning has also occurred following irrigation of serous cavities with boric acid solutions.

The commercially available boric acid ointment for topical use should not be applied to the eye. Boric acid ointment should not be used in children younger than 2 years of age unless directed by a physician. Boric acid ointment should be discontinued and a physician or pharmacist consulted if local irritation occurs during use.

Acute Toxicity

Manifestations

Following percutaneous or transmucosal absorption or ingestion, boric acid can produce severe and fatal poisoning, consisting of GI disturbances, erythematous skin eruptions, and signs of CNS stimulation followed by depression. GI disturbances include nausea, vomiting, diarrhea, epigastric pain, and hemorrhagic gastroenteritis; vomiting is often persistent. Erythematous skin eruptions, which may occur at any site, are followed by extensive exfoliation. Weakness, lethargy, headache, restlessness, tremors, twitching of facial muscles and extremities, and seizures may occur, followed by CNS depression. Metabolic acidosis and intravascular coagulation have occurred. Fever may also be present. In severe and fatal poisonings, oliguria, anuria, and renal tubular necrosis may occur. Rarely, hepatomegaly and jaundice have been reported. Cyanosis, shock, circulatory collapse, and death may result; death may occur within a few hours but is usually delayed several days. Toxicity data is somewhat unpredictable. In adults, the mean lethal dose of boric acid probably exceeds 30 g, but death has occurred with lower doses. In neonates, death has occurred with doses of 4.5 g or more.

Treatment

Treatment of acute boric acid intoxication consists mainly of intensive symptomatic and supportive therapy. If the drug was ingested, the stomach should be emptied immediately, by ipecac syrup-induced emesis if the patient is alert, or by gastric lavage with warm water. If the patient is comatose, having seizures, or lacks the gag reflex, gastric lavage may be performed if an endotracheal tube with cuff inflated is in place to prevent aspiration of vomitus. Administration of activated charcoal and a saline cathartic may also be useful. Any boric acid on the skin or mucous membranes should be removed by washing. If necessary, an airway should be established and respiration maintained. Appropriate fluid and electrolyte therapy should be administered. Seizures may be controlled with a benzodiazepine (e.g., diazepam) or a short-acting barbiturate. Hepatic and renal function should be monitored. Peritoneal dialysis, hemodialysis, and exchange transfusions have been used with some success in enhancing the elimination of borate.

Pharmacology

Boric acid possesses fungistatic and weak bacteriostatic properties. In the form of an ointment, the drug has greater bacteriostatic activity in bases containing large amounts of water than in fatty bases.

Chemistry

Boric acid is a weak topical anti-infective agent. Boric acid occurs as colorless, odorless scales with a somewhat pearly luster, as crystals, or as a white powder that is slightly unctuous to the touch. Boric acid has solubilities of 0.056 g/mL in water or alcohol and 0.25 g/mL in glycerin or boiling water. The drug is stable in air.

Additional Information

The American Society of Health-System Pharmacists, Inc. represents that the information provided in the accompanying monograph was formulated with a reasonable standard of care, and in conformity with professional standards in the field. Readers are advised that decisions regarding use of drugs are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and that the information contained in the monograph is provided for informational purposes only. The manufacturer’s labeling should be consulted for more detailed information. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information contained in the monograph is not a substitute for medical care.

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

Medical Disclaimer