Monograph: |
Boric Acid
Odourless colourless brilliant plates, or white crystals, somewhat pearly lustrous scales, or white crystalline powder, unctuous to the touch. It volatilises in steam. Soluble 1 in 18 of water, 1 in 4 of boiling water, 1 in 18 of alcohol, 1 in 6 of boiling alcohol, and 1 in 4 of glycerol. Boric acid forms a complex with glycerol which is a stronger acid than boric acid. A 3.3% solution in water has a pH of 3.8 to 4.8.
CAUTION. Pharmacists are advised not to sell boric acid as such for use as a dusting-powder. Dusting - powders containing more than 5% of boric acid should be labelled; 'not to be applied to raw or weeping surfaces'. Pharmacists are also advised not to supply Borax Glycerin or Honey or Borax, even with an appropriate warning, because of the hazards associated with the use of these preparations in infants.
Adverse Effects and Treatment
The main symptoms of acute Boric Acid poisioning are vomiting and diarrhoea, abdominal pain, an erythematous rash involving both skin and mucous membranes, followed by desquamation, and stimulation or depression of the central nervous system. There may be convulsions and hyperpyrexia. There may also be renal tubular damage. Abnormal liver function and jaundice have been reported rarely. Death, resulting from circulatory collapse and shock, may occur within 3 to 5 days.
The slow excretion of Boric Acid can lead to cumulative toxicity during repeated use. Symptoms of chronic intoxication include anorexia, gastro-intestinal disturbances, debility confusion, dermatitis, menstrual disorders, anaemia, convulsions, and alopecia.
Fatalities have occurred most frequently in young children after the accidental ingestion of solutions of Boric Acid or after the application of Boric Acid powder to abraded skin. The concentration of Boric Acid in talcs and products for oral hygiene is limited in the UK to 5 and 0.5% respectively and talcs must be labelled 'not to be used for children less than 3 years old'.
In the UK the concentration of Boric Acid in other cosmetic products is limited to 3%. Topical preparations of Boric Acid should not be applied to extensive areas of abraded or damaged skin.
Deaths have resulted from absorption following lavage of body cavities with solutions of Boric Acid, and this practice is no longer recommended.
Inhaled Boric Acid and borax are pulmonary irritants.
Treatment of poisoning is symptomatic. The stomach should be emptied if a large amount of Boric Acid has been ingested ; activated charcoal is not effective. Peritoneal dialysis or haemodialysis may be of value.
Pharmacokinetics
Boric Acid is absorbed from the gastro-intestinal tract, from damaged skin, from wounds, and from mucous membranes. It does not readily penetrate intact skin. About 50% of the amount absorbed is excreted in the urine within 12 hours ; the remainder is probably excreted over 5 to 7 days.
Uses and Administration
Boric Acid possesses weak bacteriostatic and fungistatic properties ; it has generally been superseded by more effective and less toxic disinfectants. It is used as a pesticide against ants and cockroaches.
Boric Acid is used, usually with borax as a buffer and antimicrobial in eye drops and was formerly used as a soluble lubricant in solution-tablets. Boric Acid and borax are not used internally.
In the UK the use of Boric Acid in cosmetics and toiletries is restricted.
Boric Acid is used similarly to Borax and has also been used externally as a mild astringent and as an emulsifier in creams. Borax Acid Glycerin and Honey of Borax were formerly used as paints for the throat, tongue, and mouth, but should not be used due to the risk of toxicity.
Other salts of Boric Acid including potassium and zinc salts, have been used.
Antimicrobial activity. Evuluation of the antimicrobial activity of 1.22% borate buffer.
Urine preservation. Boric Acid in concentration of about 2% may be a suitable preservative for urine samples in transit requiring bacteriological examination.
Vaginitis. Satisfactory clinical and mycological responses to Boric Acid were reported in 2 patients with candida glabrata vaginitis who had not responded to repeated courses of azole antifungals.
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