Evaluation of propofol wastage and disposal in routine anesthesia care

Pharmaceutical waste is an important and growing environmental concern. Many drugs have been detected in significant concentrations in waterways, and they are likely to be particularly harmful when “constantly introduced to aquatic ecosystems,” such as drugs inappropriately discarded on a daily basis. ¹ Environmental contamination with pharmaceuticals has consequences for wildlife and fragile ecosystems, and unquantified risks to human health due to exposure via food and water.

Anaesthetists carefully titrate medication doses for individual patients based on observed clinical effects. Unused medication from standardised ampoule volumes require disposal. ² These discarded unused drug solutions represent an inefficient (and thus low value) use of resources, contributing to unnecessary financial and environmental costs from pharmaceutical production and the supply chain. Pharmaceuticals account for 19% of total carbon emissions from Australia’s healthcare system, with healthcare representing 7% of national emissions. ³ Wastewater contamination from pharmaceutical manufacturing is also well-documented and is likely to increase with greater procurement volumes necessitated by drug wastage. ⁴

Propofol has received considerable attention as a potentially more environmentally friendly drug for maintenance of general anaesthesia. The life cycle greenhouse gas emissions associated with propofol total intravenous anaesthesia (TIVA) are several orders of magnitude lower than with inhalational anaesthetic agents. ⁵ However, propofol itself is an environmental hazard. It accumulates in fats, is toxic to aquatic life, and is not readily biodegradable. ⁶ In the human body, propofol is extensively metabolised, with <1% excreted unchanged, ⁷ however, it requires incineration to be destroyed ex vivo. While the true extent and nature of its biotoxicity remains uncertain, it is considered overall to have ‘low’ environmental risk. ⁸

In anaesthesia, propofol is one of the most common drugs that is prepared in syringes in volumes that are incompletely utilised for a given patient. ² Observed wastage ranges from 32%–50%,^6,9 accounting for 45% of total operating theatre drug waste in one study. ⁶ Other propofol life cycle considerations, including sourcing and transport of constituents (e.g. soybean oil) and single-use plastics (syringes, infusion tubing, processed electroencephalogram monitors, etc.), also contribute to the environmental impact and healthcare costs. ¹⁰

In Australia, the Environment Protection Authority requires pharmaceutical waste to be incinerated for the protection of human and environmental health. ¹¹ Further regulation of pharmaceutical waste is state/territory specific. In Victoria, the relevant legal frameworks are the Drugs, Poisons and Controlled Substances Act 1981 ¹² and Drugs, Poisons and Controlled Substances Regulations 2017. ¹³ These require that Schedule 8 (S8) medicines and Schedule 4 Drugs of Dependence be destroyed by an authorised health practitioner and witnessed by a second authorised health practitioner. There are exceptions to the witnessing requirement, such as when destroying a vial of previously sterile medicine, however it is still encouraged to reduce risks of diversion.

The Victorian Department of Health and Human Services recommends that discarded S8 medications are rendered non-recoverable and non-identifiable, ¹⁴ and requires that containers for S8 medicines are considered to be pharmaceutical waste and disposed of in the same manner.

The use of approved pharmaceutical waste receptacles can support compliance with these regulatory frameworks and ensure unused medications are directed to appropriate waste streams. However, these may not be available in all locations where pharmaceuticals are commonly discarded (e.g. operating theatres). Pharmaceutical waste thus ends up in sharps bins or general waste (or occasionally clinical waste or the sink), none of which are suitable for avoiding environmental contamination and all have limited efficacy in preventing diversion. This represents both an environmental risk and a potential legal risk for these institutions.

To obtain contemporaneous local data on propofol waste, a prospective observational study was conducted at two tertiary teaching hospitals in Melbourne (Western Health HREC reference no. QA2021.72_78411). The volume of propofol opened, volume discarded and site of discarding in all cases in which propofol was used across 11 operating theatres and three procedure rooms was recorded over one week (conducted sequentially at the two sites). This included elective and emergency cases, adult and paediatric cases, and anaesthesia for either sedation or general anaesthesia (TIVA, inhalational and mixed). All data, including volumes to the nearest millilitre, were entered directly into REDCap (Vanderbilt University, Nashville, TN, USA) data forms by the anaesthetist or anaesthetic trainee managing the case.

Data were collected for 119 cases, with a total of 7910 ml propofol opened and 1809 ml (23%) discarded. Using a simple estimate of annual use by multiplying the sample values by 52 (weeks), this equates to 94,693 ml discarded at a cost of A$3,693 per year (A$0.039 per ml, calculated as an average value of A$0.041/ml for 20 ml vials, A$0.039/ml for 50 ml vials, and A$0.037/ml for 100 ml vials).

In our study, 40% of propofol was discarded in the sharps bin and 60% in general waste. No dedicated pharmaceutical waste bins were available. Introduction of pharmaceutical waste bins would improve compliance with regulatory requirements and reduce environmental contamination risks, however, there would also be additional associated costs and environmental impacts (e.g. from the production and transport of the pharmaceutical waste bins). An appraisal of the available pharmaceutical bins is presented in the Victorian Framework for handling and disposal of Pharmaceutical Waste, though the Victorian Therapeutic Advisory Group notes that “a bin fulfilling all legislative and practical requirements may not currently be available”. ¹⁵

Some drug wastage is inevitable, but minimising waste and optimising drug disposal can improve the sustainability of our practice. Reductions in propofol wastage may be achieved through audits with feedback to clinicians, using smaller propofol ampoules ⁶ and minimising pre-emptive drawing up. Accurately predicting case duration could also reduce waste when using TIVA or propofol sedation and may improve with clinical experience and when working with a familiar proceduralist. Novel technology such as the Propofol Dreams app ¹⁶ may assist in predicting propofol requirements. For cases with small propofol requirements (e.g. electroconvulsive therapy lists), splitting of vials between patients may reduce waste—a practice that is discouraged, though considered acceptable in some circumstances, by the Australian and New Zealand College of Anaesthetists. ¹⁷ Anaesthetists can play an important role in reducing our financial and environmental impact through the many small choices we make daily.