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End the ice age - Is glacial acetic acid really needed?

From the May 5, 2005 issue

"POISON! DANGER! CORROSIVE. Liquid And Mist Cause Severe Burns To All Body Tissue. May Be Fatal If Swallowed. Harmful If Inhaled. Inhalation May Cause Lung And Tooth Damage."

Problem: That's exactly what it says in the warning statements next to the red skull and crossbones on the label of glacial acetic acid (pure acetic acid). Still, as strong as these warning statements are, they haven't prevented occasional accidents in which glacial acetic acid is dispensed from the pharmacy instead of a diluted form.

The word "glacial" (ice-like) refers to the fact that, at its freezing point of 17 degrees Celsius, pure acetic acid forms crystals and "freezes," looking like a glacier. Diluted forms of acetic acid are used to treat certain infections of the outer ear and the ear canal (e.g., DOMEBORO OTIC is 2%), and to identify cervical dysplasia during colposcopy (3-5% solution) after an abnormal Pap smear. Vinegar is 5% acetic acid; this concentration has also been used medically for irrigation. A 0.25% concentration of acetic acid is commercially available as a premixed irrigation, used primarily in bladders and wounds.

In one case of dispensing an undiluted form, a nurse called the pharmacy for "acetic acid for irrigation" for a 31-year-old patient with paraplegia, osteomyelitis, and bilateral greater trochanter wounds. An experienced pharmacist, yet new to the institution, placed glacial acetic acid at the window for pickup. This was used for 2 days instead of an appropriate diluted form. The undiluted solution resulted in burns to the extent that the wounds would not heal, necessitating disarticulation at the hips.

In another hospital where the pharmacy routinely restocks automated dispensing cabinets (ADCs) for patient care areas, a recent refill request for the ambulatory surgery center called for 30 mL of a 5% acetic acid solution. A pharmacy technician obtained the bulk bottle of glacial acetic acid and poured 30 mL directly into a 1 ounce bottle. The technician was unaware that the product required dilution to make a 5% solution. The technician labeled the bottle as "acetic acid - glacial." The pharmacist who checked the technician's work was aware of the need for dilution but, despite the label, he assumed that the technician had already performed the required dilution. The bottle was then placed into stock in the ambulatory surgery department's ADC and later removed by nursing staff for administration to a patient. The nurses and physician assumed the product had been diluted and did not notice that "5%" was not listed on the label. As a result, the physician used the glacial acetic acid during a colposcopy. The patient experienced immediate vaginal bleeding and blistering after the solution was applied, and then severe pain when she awoke from sedation. The physician did not immediately recognize the error, but he quickly realized that something was wrong as soon as he applied the acetic acid. The harm to the patient was temporary, but she required a week off from work to recover.

In yet another case, a bottle of what should have been 3% acetic acid was sent to the operating room. However, it was actually glacial acetic acid. One patient's skin was bathed with the solution, causing first and second degree burns.

Safe Practice Recommendation: Based on these and other reports, it seems clear that a knowledge deficit exists among some health professionals with respect to the properties of glacial acetic acid. Some staff members may not recognize that glacial refers to the most concentrated form of acetic acid. E-mail this newsletter, or use it during staff meetings, to assure that clinicians are aware of the differences between various concentrations of this product. Although the warning on the bottle seems clear, it may not be noticed. Keep in mind, this product is packaged and labeled as a commercial chemical. It is not a drug, and FDA approval is not required. If this product must be maintained in inventory at all, it would be helpful if more prominent alert messages were placed on both the shelf and the bottle itself. One hospital uses a neon-colored warning label that they designed themselves.

Another causative factor in the events described above is the lack of an independent double check when dangerous chemicals are handled. In one case, a pharmacist checked the technician's work but only assumed that a dilution had been made. There was no actual observation to reliably draw that conclusion. No matter who prepares a dilution using glacial acetic acid, recipes must be readily retrievable to detail how the dilutions should be made and an independent double check must be made of all materials, calculations, and measurements, as well as labeling.

Some errors also appear to be related to the manner in which the drug is prescribed, such as not including the necessary strength or mentioning glacial acetic acid in the order (e.g., "dilute glacial acetic acid" is one way it's been written.) In fact, in some cases, no order is even written; acetic acid is just considered a chemical that can be requested without an order. Obviously an order should be required, and the exact strength necessary must be included. Requests to dilute glacial acetic acid should be made at least 1 day before it is needed to remove the urgency of trying to honor unfamiliar requests.

One of our strongest recommendations during our hospital consults has been to remove and discard unnecessary chemicals from the compounding area within the pharmacy, particularly those that have not been used within the last 6 months to a year. This is often the case with glacial acetic acid. In many cases, one of the aforementioned commercial preparations can be used. In some cases, you may be able to use standard table vinegar (5% acetic acid). If bulk chemicals must remain in stock, store them in a locked, sequestered section of the pharmacy. Another option is to dilute the product in the concentrations needed immediately upon delivery of the chemical. Thus, there would be no undiluted product in stock.

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