Brief clinical and laboratory observation

Propylene glycol: A potentially toxic vehicle in liquid dosage form

Newborn babies can require significant amounts of medication containing excipients intended to improve the drug formulation. Most medicines given to neonates have been developed for adults or older children and contain excipients thought to be safe in these age groups. Many excipients have been used widely in neonates without obvious adverse effects. Some excipients may be toxic in high amounts in which case they need careful risk assessment. Alternatively, it is conceivable that ill-founded fears about excipients mean that potentially useful medicines are not made available to newborn babies. Choices about excipient exposure can occur at several stages throughout the lifecycle of a medicine, from product development through to clinical use. Making these choices requires a scalable approach to analysing the overall risk. In this contribution we examine these issues.

Although most adverse drug reactions are caused by the active substances, excipients may sometimes affect the safety profile of a medicinal product.

The aim of this review is twofold: (1) To identify the excipients most frequently contained in oral medicinal products marketed in Italy for gastrointestinal indications, and to evaluate the main safety concerns, considering both intrinsic toxicity and patient-related risk factors. (2) To analyze possible differences with medicinal products marketed in the United Kingdom and USA in terms of excipients and relevant warnings reported in the label.

We identified excipients with potential impact on safety profile and calculated frequency of use of each identified excipient in 98 selected medicinal products. We discussed possible safety concerns in clinical practice. We also analyzed US and UK Summary of Products Characteristics (SmPC) of oral gastrointestinal products by searching in appropriate collections of regulatory agencies.

Eleven excipients with a safety impact were identified (sucrose, saccharin, aspartame, sorbitol, mannitol, lactose, ethanol, propylene glycol, parabens, menthol and silica) and no substantial differences were found between drugs marketed in the three countries concerning excipient content.

Warnings were more detailed in the SmPC of UK or USA products rather than Italian products.

Information about pharmaceutical excipients with known effects is important in clinical practice, but the frequent lack of details in the related section of the SmPCs makes it difficult for health professionals to provide relevant advice.

The availability of alternative products of the same therapeutic class, but lacking specific excipient(s) should be considered in selected patients.

Benzodiazepines are commonly administered to medical ICU (MICU) patients. Propylene glycol (1,2-propanediol) is the solvent used to deliver lorazepam and diazepam IV. Although propylene glycol toxicity is increasingly recognized and reported, its incidence is unknown. Herein, we describe five MICU patients who acquired severe propylene glycol toxicity due to IV lorazepam or diazepam administration. Additionally, we evaluate the incidence of propylene glycol toxicity in MICU patients receiving IV lorazepam or diazepam.

Case series and prospective, observational study.

Eighteen-bed MICU in a 550-bed urban academic hospital.

MICU patients administered IV benzodiazepines during a 3-month period were enrolled. Patients were categorized according to the IV benzodiazepine that they received. Laboratory data and highlights of their clinical course were recorded daily. The incidence of propylene glycol toxicity was determined and the groups compared.

Forty-four patients were enrolled. Twenty-one patients received a benzodiazepine delivered in propylene glycol (lorazepam or diazepam), and 23 patients received a benzodiazepine delivered in an alternative solvent (midazolam). We found that four patients (19%) who received IV lorazepam or diazepam had metabolic evidence of propylene glycol toxicity. None of the patients had clinical deterioration. Neither metabolic abnormality nor clinical deterioration suggestive of propylene glycol toxicity were identified in subjects receiving IV midazolam.

Propylene glycol toxicity is a potentially life-threatening iatrogenic complication that is common and preventable. It should be considered whenever a patient has an unexplained anion gap, unexplained metabolic acidosis, hyperosmolality, and/or clinical deterioration. Close monitoring of all patients receiving IV lorazepam or diazepam for early evidence of propylene glycol toxicity is warranted.