Glacial acetic acid is the trivial name used to refer to pure acetic acid in an anhydrous state. It is a colorless, hygroscopic, weak acid that is available in concentrations of 99.5% to 100%. Similar to the German name Eisessig (ice-vine-gar), the word “glacial” is derived from the ice-like crystals that form at 16.6°C (61.9°F), slightly below room temperature.¹ Although classified as a weak acid, glacial acetic acid is a corrosive poison that can cause injury or death when human tissue is exposed to it. At concentrations of 10% to 25% (1.67-4.16 mol/L), it acts as an irritant; but at concentrations greater than 25% (>4.16 mol/L), it is corrosive and should be handled in a fume hood.² Skin contact may produce blistering or burns, while liquid or spray mist may produce tissue damage particularly on mucous membranes of the eyes, mouth, and respiratory tract.³

Acetic acid has been used for centuries in food production, manufacturing, cleaning, and even medical purposes. Generally, undiluted glacial acetic acid has no medical use, but a review of the literature reveals that acetic acid in diluted concentrations has been used for a variety of indications. Diagnostically, such indications include oral screening and lesion identification⁴ (1%, mouth rinse) and Barrett’s esophagus⁵ (1.5%-2.5%, spray). As treatment, it has been used for bladder and wound irrigation⁶ (0.25%-0.5%, irrigation solution). Slightly higher concentrations have been used for otitis externa,⁷ iontophoresis,⁸ ear wax removal,⁹ and cervicoscopy after an abnormal Pap smear¹⁰ (1%-5%, topical solution). Controversially, it has also been used for wound infections,¹¹ vaginal douching,¹² and as a neutralizing diluting agent for alkali skin burns.¹³ Yet even more concentrated, acetic acid has a place in renal cyst sclerotherapy¹⁴ and hepatocellular carcinoma¹⁵ (50%, injection).

A number of acetic acid products are commercially available. Prediluted, ready-to-use USP formulations include products such as acetic acid/aluminum acetate otic and premixed irrigation solutions. Dietary vinegar (5%) has also been used medically for irrigation and topical application. Sometimes, however, concentrated chemical-grade glacial acetic acid is used, but it requires a pharmacist’s skill to compound and dispense before it is acceptable for human use. Despite warning labels on the container, repeated incidents of concentrated glacial acetic acid being dispensed instead of a diluted form have caused patient injury. We describe 2 reports of injuries due to glacial acetic acid and a review of the literature of similar cases with recommendations for patient safety. 

CASE REPORTS

Patient Case 1

A 59-year-old female was admitted to the hospital to undergo a wide local excision of a lesion on her vulva. Acetic acid 4% was to be used in the procedure to demarcate the abnormal epithelium. Although there was confusion over whether the strength ordered electronically was 0.25% or 4%, ultimately the order that was delivered to the operating room was prepared by the pharmacist as acetic acid 80%. No explanation was given regarding how this difference occurred. The acetic acid solution was poured onto the indicated area; within a minute of application, a strong acetic acid smell was noted. The surgeon requested the strength of the solution be verified, and an inspection of the label visible on the bottle indicated acetic acid 80%. The procedure was terminated and 4 L of normal saline was used to irrigate the area, followed by an injection of bupivacaine 0.25% with epinephrine 1:200,000 and the application of silver sulfadiazine cream. The patient experienced second-degree partial thickness chemical burns on her labia minora and majora, perineum, rectum, and sacrum extending to the lower lumbar back. Subsequent treatment included topical lidocaine, triple antibiotic cream, and oral opiate analgesia and antibiotics. 

Patient Case 2 

A 50-year-old male paraplegic who had an indwelling suprapubic catheter developed problems with the build-up of particulate matter in the catheter. Acetic acid solution 0.25% was ordered for catheter clearance, but an error occurred when the telephone order was placed resulting in a prescription for acetic acid 25%. Because the pharmacist had never compounded an acetic acid solution at that -concentration, he declined to dispense the prescription and referred the patient back to his physician. Because the prescribing physician was unavailable, a covering physician recommended the patient wait to speak with the prescriber because there was confusion over the order. However, the patient was not advised that a 25% acetic acid solution posed a danger. In the interim, the patient went to a different pharmacy that agreed to compound the prescription. The pharmacist filling the prescription did not question the strength, even though they later stated that they knew it was inappropriate for the intended purpose. Use of the 25% solution caused severe burns to the urethra and bladder and “melted” the catheter around the patient’s penis. The patient required inpatient treatment, after which he chronically complained of burning sensations in his penis and bladder. 

DISCUSSION

Multiple reports have been published advising of the dangers associated with the use of glacial acetic acid in clinical patient care. Table 1 summarizes 18 cases of injury that have been reported in the literature.^16-27 An additional report appears in the literature of 5 women who were treated in a colposcopy clinic with glacial acetic acid instead of acetic acid 5% as a result of a computer entry error, although no detectable harm was reported.²⁸

As can be seen from these cases, serious patient harm has resulted from the use of concentrated glacial acetic acid. Root cause analyses have revealed that problems associated with inaccurate medication reconciliation; improper prescribing, dilution, and labeling; inappropriate packaging; an absence of checks and balances; inadequate drug information resources; and lack of familiarity regarding the properties of glacial acetic acid are -common causes of errors among health care providers. Other causes have been attributed to the fact that glacial acetic acid is not a drug and therefore not regulated by the US Food and Drug Administration (FDA). Thus, precautionary labels applied to product packaging by the chemical industry (Figure 1)²⁹
are often inconsistent, inconspicuous, or even absent when compared to those customarily seen on FDA-approved drugs.

Based on these findings, several patient safety strategies have been recommended in an effort to avoid incidents with glacial acetic acid. These recommendations are gathered from previous ISMP Medication Safety Alert! publications and other case reports^19-23,30 and have been organized according to ISMP’s Key Elements of the Medication Use System³¹ (Table 2). This set of recommenda-tions can serve as a tool for managing this recurring problem. 

CONCLUSIONS 

The storage and use of glacial acetic acid inherently poses a potential danger and can cause patient injury when not properly diluted. Medication safety experts have advocated for several strategies that can mitigate the risk, for both patients and health care providers, involved in the use of this chemical. The -application of these strategies to the medication use process can work to establish a system with fail-safes that prevent glacial acetic acid from reaching the patient.

ACKNOWLEDGMENTS

The authors declare no conflicts of interest. Mr. Richmond has provided expert testimony as a pharmacist through The Mackenzie Group, LLC.  

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^*Hickory Hill Pharmacy, Helena, Arkansas; ^?Walgreens, Middletown, Kentucky; ^‡The Mackenzie Group, LLC, Searcy, Arkansas; ^§Harding University College of Pharmacy, Searcy, Arkansas. Drs. Doles and Wilkerson and Ms. Morrison completed this work while serving as a doctor of pharmacy candidates at Harding University College of Pharmacy. Corresponding author: Rodney G. Richmond, MS, CGP, FASCP, Associate Professor, Pharmacy Practice, Harding University College of Pharmacy, 915 East Market Street, Box 12230, Searcy, AR 72149; phone: 501-279-4858; e-mail: rrichmond@harding.edu