Propofol compatibility with other intravenous drug products: two new methods of evaluating IV emulsion compatibility

Consistency of remifentanil concentrations in propofol-Remifentanil infusions. A laboratory-based study

BACKGROUND

There is increasing interest in two-agent single-pump intravenous infusions for anesthesia and sedation in pediatric patients. Propofol-remifentanil is one such mixture. The poor miscibility of such admixtures when remifentanil is added in very high concentrations and when the admixtures are maintained in static conditions has been demonstrated; however, these physiochemical properties have not been examined in clinically relevant concentrations or settings.

AIM

To examine if propofol-remifentanil admixtures maintain consistent remifentanil delivery when mixed in clinically relevant remifentanil concentrations and subjected to the physical effects of an actively infusing, directly-engaged syringe driver system with an extension line, as occurs when propofol-remifentanil is administered to a patient.

METHODS

A propofol 10 mg.ml^-1 combined with remifentanil 5 mcg.ml^-1 solution was run using a Paedfusor^® propofol target-controlled infusion model for 10 kg and 20 kg children for 57 min at a target plasma concentration of 3 mcg.ml^-1 through a 30 ml syringe, 180 cm minimum volume extension line, lever lock cannula, interlink injection site, and 22 g intravenous cannula into sample pots. Samples were taken at the completion of the loading bolus, 1 and 2 min postcompletion of loading bolus, and every 5 min thereafter. The remifentanil concentration in these samples was then assayed using chromatography.

RESULTS

There was no difference in the concentration of remifentanil in the samples based on the duration of infusion to the endpoint of 1 h, or on the patient weight model used. The concentration remained 5 mcg.ml^-1 +/- 0.5 mcg.ml^-1 per sample. The measurement uncertainty for the assay at 0.5 mcg.ml^-1 is +/- 0.2 mcg.ml^-1 .

CONCLUSION

The concentration of remifentanil was 5 mcg.ml^-1 +/- 0.5 mcg.ml^-1 and was consistent across 57 min of infusion, and two different pediatric weight profiles.

Clinical Pharmacokinetics and Pharmacodynamics of Propofol

Propofol is an intravenous hypnotic drug that is used for induction and maintenance of sedation and general anaesthesia. It exerts its effects through potentiation of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) at the GABAA receptor, and has gained widespread use due to its favourable drug effect profile. The main adverse effects are disturbances in cardiopulmonary physiology. Due to its narrow therapeutic margin, propofol should only be administered by practitioners trained and experienced in providing general anaesthesia. Many pharmacokinetic (PK) and pharmacodynamic (PD) models for propofol exist. Some are used to inform drug dosing guidelines, and some are also implemented in so-called target-controlled infusion devices, to calculate the infusion rates required for user-defined target plasma or effect-site concentrations. Most of the models were designed for use in a specific and well-defined patient category. However, models applicable in a more general population have recently been developed and published. The most recent example is the general purpose propofol model developed by Eleveld and colleagues. Retrospective predictive performance evaluations show that this model performs as well as, or even better than, PK models developed for specific populations, such as adults, children or the obese; however, prospective evaluation of the model is still required. Propofol undergoes extensive PK and PD interactions with both other hypnotic drugs and opioids. PD interactions are the most clinically significant, and, with other hypnotics, tend to be additive, whereas interactions with opioids tend to be highly synergistic. Response surface modelling provides a tool to gain understanding and explore these complex interactions. Visual displays illustrating the effect of these interactions in real time can aid clinicians in optimal drug dosing while minimizing adverse effects. In this review, we provide an overview of the PK and PD of propofol in order to refresh readers' knowledge of its clinical applications, while discussing the main avenues of research where significant recent advances have been made.

Compatibility of drugs administered as Y-site infusion in intensive care units: A systematic review

OBJECTIVES

To gather all published information about the stability of drugs commonly used in Intensive Care Units (ICU); evaluate the methodology of published data; and generate a compatibility table.

DESIGN

i) A systematic review was conducted searching the following databases: Medline, Stabilis, Handbook of Injectable Drugs and Micromedex. Articles published from 1990 to 2017 in English, Spanish and French were included. ii) Article quality was analyzed according to the stability studies practice guidelines. iii) A compatibility table was produced with data for 44 binary combinations of drugs frequently used in the ICU.

SCOPE

Spanish and international hospital ICU.

RESULTS

The systematic review included 29 studies (27 originals, 2 reviews). None of the included studies followed all the methodological requirements. However, 93% guaranteed correct reproducibility. Accordingly, drug stability knowledge was available for 50.3% of the studied admixtures, in which 77.1% of the binary combinations proved compatible and 16.8% proved incompatible.

CONCLUSIONS

This review provides new reliable evidence about the physicochemical stability of drugs commonly used in the critical care setting. The study contributes to the safe administration of intravenous drugs in critical patients with a view to avoiding adverse events in this frail population.

Stability of azasetron-dexamethasone mixture for chemotherapy-induced nausea and vomiting administration

Combination antiemetic therapy has become common practice for the prevention of nausea and vomiting caused by anticancer drugs. In this study, we investigated the stability of azasetron hydrochloride 0.1 mg/mL plus dexamethasone sodium phosphate 0.05, 0.1, or 0.2 mg/mL in 0.9% sodium chloride injection and stored in polyolefin bags and glass bottles over a period of 14 days at 4°C and 48 hours at 25°C. The stability studies were evaluated by visual inspection, pH measurement, and a high-pressure liquid chromatography assay of drug concentrations. During the study period, the concentration of each drug in the various solutions remained above 97% of the initial concentration at both 4°C and 25°C when protected from room light. Under the condition of 25°C with exposure to room light, the concentrations of both drugs were significantly lowered over 48 hours. The pH value decreased, and the color changed from colorless to pink. Our study demonstrates that the azasetron-dexamethasone mixture at a clinically relevant concentration seems to be stable for 48 hours at 25°C and for 14 days at 4°C when packaged in polyolefin bags or glass bottles and protected from room light. The room light is the main influential factor on stability. Clinicians should be aware that combinations of azasetron hydrochloride and dexamethasone sodium phosphate in solution with light exposure should be avoided.

Physicochemical compatibility and emulsion stability of propofol with commonly used analgesics and sedatives in an intensive care unit

Objectives

The purpose of this study was the determination of the physicochemical compatibility and emulsion stability of propofol with other sedatives and analgesics (clonidine hydrochloride, dexmedetomidine, 4-hydroxybutyric acid, (S)-ketamine, lormetazepam, midazolam hydrochloride, piritramide, remifentanil hydrochloride and sufentanil citrate) that are frequently administered together intravenously.

Methods

Drugs were mixed with propofol and stored without light protection at room temperature. Samples were taken at 10 points of time over 7 days. The physical stability and emulsion stability in particular were analysed by visual and microscopical inspection and by measurement of the pH value, zeta potential and globule size distribution. In addition, high-performance liquid chromatography and mass spectrometry were used to identify chemical incompatibilities.

Results

4-Hydroxybutyric acid, midazolam hydrochloride, piritramide and remifentanil hydrochloride are physically incompatible when mixed with propofol. The reason for this is the development of an increased fraction of oil droplets >5 µm leading to a higher risk of emboli. Moreover, propofol is chemically incompatible with remifentanil. The sorption of propofol to the rubber stopper of the syringe was another detectable incompatibility.

Conclusions

Propofol should not be administered with 4-hydroxybutyric acid, remifentanil hydrochloride, midazolam hydrochloride and piritramide through the same intravenous line. Based on the risk of sorption to the rubber material, propofol should be used with caution. A drug loss might occur that leads to an underdosing of the patient requiring a dose adjustment to avoid any adverse consequences. As a result of this study, the drug safety in intensive care units could be optimised.

Standardization of infusion solutions to reduce the risk of incompatibility

PURPOSE

Although critically ill patients usually have various central intravenous (i.v.) lines, numerous drugs have to be infused simultaneously through the same lines. This can result in potentially harmful in-line incompatibility that can cause decreased drug effectiveness or increased microparticle load. To minimize the risk of these medication errors at an anesthesia intensive care unit (ICU), the preparation and administration of continuously infused drugs were standardized and the practicability in daily clinical routine was evaluated.

SUMMARY

The concentration and diluent of continuously administered i.v. drugs were standardized. The drugs were grouped according to pH, medical indication, and chemical structure. The ICU staff decided to use multilumen central venous catheters, and each group of drugs was assigned to one lumen. Only drugs that belonged to the same group were infused simultaneously through the same lumen; therefore, intragroup incompatibilities had to be excluded before establishing the new drug administration plan at the ICU. The visual compatibility of 115 clinically reasonable intragroup drug mixtures was investigated. All drug combinations were compatible for six hours except mixtures containing thiopental, which was reassigned to a single-line use. In the following year, the practicability of this drug administration plan was evaluated. No deviations were found in the compliance of the staff prescribing and preparing only standardized concentrations and diluents. Further research to investigate the chemical compatibility of the drugs in these multiple mixtures will follow.

CONCLUSION

A project intended to avoid incompatibility among i.v. drugs infused in the intensive care setting included steps to standardize solutions and determine which could be given together.

Adverse Events Associated with Sedatives, Analgesics, and Other Drugs That Provide Patient Comfort in the Intensive Care Unit

Since the 2002 publication of multidisciplinary clinical practice guidelines for intensive care unit (ICU) sedation and analgesia, additional information regarding adverse drug events has been reported. Our understanding of the risks associated with these sedative and analgesic agents promises to improve outcomes by helping clinicians identify and respond to therapeutic misadventures sooner. This review focuses on many issues, including the potentially fatal consequences associated with the propofol infusion syndrome, the evolving understanding of propylene glycol intoxication associated with parenteral lorazepam, new data involving high-dose and long-term dexmedetomidine therapy, haloperidol- and methadone-related prolongation of QTc intervals on the electrocardiogram, adverse events associated with atypical antipsychotics, and the potential for nonsteroidal antiinflammatory drugs to interfere with bone healing.