Advil and amoxicillin

It has been demonstrated that continuous infusion maintains concentrations above the MIC for a longer period of time within the dosing interval [6].

Moreover, mounting evidence from clinical studies indicates that continuous infusion of time-dependent ?-lactam antibiotics may improve clinical success [7–9]. Therefore it may be well-founded to administrate ?-Lactams using continuous infusion in patients suffering from serious infectious disease. However, despite the possible clinical benefits of this mode of administration, one of the practical concerns related to continuous infusion is the limited stability of certain antibiotic agents. Indeed, stability issues have to be taken into consideration when implementing drug administration, in order to ensure drug efficacy and safety. Regarding ?-lactam antibiotics, not knowing how long they remain stable during infusion may be a limiting factor for continuous administration [10,11].

Furthermore, for several decades, intravenous antimicrobials have been administered increasingly in outpatient settings, in particular thanks to the use of portable devices [12,13]. Outpatient parenteral antimicrobial therapy (OPAT) allows for early hospital discharge, and further reduces costs with fewer nursing and clinic visits [14]. Moreover, OPAT improves quality of life, and portable elastomeric pumps gives patients more flexibility and control over their treatment [15].

Among the important aspects described in OPAT practice guidelines, drug stability has been underlined as a crucial point to be taken into consideration to ensure efficacy and safety of antimicrobial therapy [12,16,17]. In a recent survey, osteomyelitis, prosthetic joint infections and endocarditis were the most commonly reported indications for OPAT [18].

In treatment of these infectious diseases, continuous infusion of high-dose amoxicillin may be limited by lack of knowledge of the chemical stability of the drug.

Indeed, very few studies are available in the literature regarding the stability of amoxicillin in aqueous solution for intravenous administration and results regarding long-term stability have been inconsistent [19–23]. The aim of this work was to propose safe and effective conditions for continuous intravenous administration of high-dose amoxicillin using portable elastomeric pumps. For that purpose we performed a comprehensive study designed to determine the chemical stability of high-dose amoxicillin solutions. Amoxicillin powder used for calibration of the method was purchased from Sigma-Aldrich (Sigma-Aldrich, France) while amoxicillin sodium powder for solution for injection, equivalent to amoxicillin 2 g, was used for the pharmaceutical preparation (Panpharma, France).

HPLC-grade methanol was obtained from Carlo Erba (Carlo Erba, France) and ultrapure water was provided using a Millipore Direct-Q 3 UV water purification system (MerckMillipore, France). Sterile water and 0.9% sodium chloride for injection were obtained from B.Braun (B.Braun, France).

Portable elastomeric pumps Infusor (48 mL, 2 mL/h) and FOLFusor (240 mL, 10 mL/h), were obtained from Baxter (Baxter, France) and portable elastomeric pumps Accufuser (480 mL, 20 mL/h) from Wym (Wym, France).

The Infusor and FOLFusor reservoirs are made of synthetic polyisoprene and the Accufuser reservoir is made of medical silicone. Amoxicillin solubility was assessed within the range 25 to 300 mg/mL by dissolving a vial of amoxicillin sodium, equivalent to amoxicillin 2 g, in adequate volume of sterile water for injection.

The vial was vortexed for 10 min, centrifugated at 3500 G for 10 min and the amoxicillin concentration was determined in the supernatant.

To determine the optimal volume of dilution for amoxicillin reconstitution, we investigated the influence of the concentration on the chemical stability of amoxicillin. Amoxicillin solutions were prepared at different concentrations in various infusion devices (Table 1). The filled elastomeric pumps were stored at 25 ± 1°C for 24 hours in amoxicillin and potassium tablets a climate chamber without humidity control (Air concept, FirLabo, France). Samples (n = 3) were collected at different times over the 24-hour storage period and determination of the amoxicillin concentration was performed immediately.

To determine the best storage conditions during amoxicillin infusion we investigated the influence of temperature on the chemical stability of amoxicillin. Amoxicillin solutions were prepared at a concentration of 125 mg/mL (6 g of amoxicillin were reconstituted with 48 ml of sterile water for injection), in order to fill an Infusor (nominal volume of 48 mL, flow rate of 2 mL/h).

The filled elastomeric pumps were then stored for 24 hours at different temperature conditions: 5 ± 2°C in a refrigerated chamber (Precision, Thermo Scientific, France), 25 ± 1°C, 30 ± 1°C and 37 ± 1°C, in a climate chamber (Air concept, FirLabo, France).

Samples (n = 3) were collected at different times over the 24-hour storage period and determination of the amoxicillin concentration was performed immediately.

Finally, the stability of amoxicillin was assessed under optimized conditions.

For this purpose, amoxicillin solutions were prepared at a concentration of 25 mg/mL (12 g of amoxicillin were reconstituted using 240 ml of sterile water for injection and 240 mL of 0.9% sodium

choride

The filled elastomeric pumps were then stored for 24 hours at room temperature (22 ± 4°C) or between 4 and 8°C in a refrigerated bag. Samples (n = 3) were collected at different times over the storage period and determination of the amoxicillin concentration was performed immediately. The degradation rate was estimated using the slope of the linear regression curve corresponding to amoxicillin remaining (% of initial concentration) versus time profile. Stability was defined as less than 10% disappearance of the amoxicillin concentration, in compliance with the provisions function of amoxicillin of the US Pharmacopoeia concerning the acceptable limit of content of drug preparation settled at 90% [24], and with the European Pharmacopoeia, requiring that ?-Lactams solutions always contain at least 90% of intact molecule [25].

All samples were diluted to a concentration of 100

?g/mL

Separation was performed using amoxicillin 250 mg uses a Nucleosil C8 analytical column (5 ?m, 150 x 4.6 mm, VWR, France).

Mobile phase consisted of 20% methanol and 80% ultrapure water; flow rate was set at 1 mL/min and 10 ?L of the diluted sample were injected onto the column.

Quantification was performed by integration of the peak at a detection wavelength of 225 nm. The stability-indicating HPLC-UV method was validated in accordance with the guidelines of the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use Q2(R1) [26]. Briefly, the method was linear over the range 0–200 ?g/mL (r 2 > 0.9993) and the limit of quantification of amoxicillin was equal to 12.5 ?g/mL.

Precision of the method was high, according to intra-day and inter-day coefficients of variation, calculated at low and high concentrations, equal to or less than 4.4% and to the trueness, assessed using the bias, ranging from 88 to 108%. To ensure that the method could be regarded as suitably stability-indicating, we checked to be sure that the decomposition products obtained from amoxicillin solution subjected to severe stress (90°C, pH 1, pH10) did not coelute with the intact drug. Degradation products of amoxicillin were investigated by accurate mass determination using high-resolution mass spectrometry (HRMS).

Briefly, amoxicillin solutions (50 mg/mL, extemporaneous and kept stored 48 hours at 37°C) were injected onto the HPLC system connected to an ultra-high definition quadrupole time-of-flight mass spectrometer (Xevo QTof, Waters, France). The mass spectrometer was equipped with electrospray source, operating in positive ion mode, using the following operating parameters: capillary voltage: 0.5 kV; sample cone voltage: 20 V; source temperature: 120°C; desolvation temperature: 600°C; cone gas flow: 50L/h; desolvatation gas flow: 1000L/h. Accurate mass measurements of main ions (Low energy: 4 eV) and fragments (high-energy ramp: 10 to 40 eV) were used to identify the major degradation products. LC-MS-measured accurate mass spectra were recorded across the range 50–1000 m/z with scan time settled at 0.1 s. The degradation products were identified by structure elucidation using the molecular ion exact mass determination and the collision-induced dissociation fragments obtained using HRMS.