Sistemas de costos por procesos

3.4.1. Freezing point depression osmolality measurement

The aim is to determine osmolality (tonicity) of a solution. The method is as follows:

 A 250 µL sample is loaded into a single use sample holder, which is then loaded into an osmometer;

 Once, the START function is initiated, the osmometer lowers a probe into the sample. The probe consists of a temperature probe and a rotating wire which is agitating the sample solution inside the sample holder, preventing it from freezing;

 The sample is cooled by running cooling fluid around the sample holder. Because the sample solution is continuously agitated, it does not freeze, even when the sample temperature goes below the freezing point of the solution. This process is known as supercooling;

 Once the sample is supercooled, the osmometer stops the slow agitation of the sample solution and shocks the sample solution by vibrating the wire in a single powerful jolt. This shock causes an immediate sample solution frozen and crystal formation. During crystal formation, the energy released is given off as heat, which can be detected by the osmometer temperature probe;

 The change in temperature from the supercooled sample point to the moment where crystallization occurs, is then automatically plotted against a regression curve produced by analysing samples of reference standards with known concentrations.

This method relies on correlation between ion content and freezing point depression. Therefore, solutions that may contain non-ion species (e.g. solvents such as ethanol) may affect the results.

The specification for isotonic solution is 290 mOsm/kg. How much a radiopharmaceutical solution can deviate from this value depends on the volume of administration, the injection rate, and the route of administration.

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3.4.2. Sodium chloride equivalent

The aim is to calculate the osmolality of a solution. The method is as follows:

 The osmolality of a solution can be calculated from its known components using the sodium chloride equivalent;

 The sodium chloride equivalent is the amount of sodium chloride which will produce the same osmotic effect as one unit of the drug;

 The concentration of each component is multiplied by its sodium chloride equivalent, and the values for each component are added up and compared to an isotonic solution of 0.9%

sodium chloride^a.

The specification for isotonic solution is 290 mOsm/kg. How much a radiopharmaceutical solution can deviate from this value depends on the volume of administration, the injection rate, and the route of administration.

3.4.3. Visual inspection

The aim is to determine the colour change and presence of any particulate matter of solution by visual inspection of the sample–batch. The method is as follows: stand behind a lead glass shield, use tongs to hold the test sample (or final product) vial against a light beam, and gently shake it to check for the presence of any particulate matter. For the colour change hold the vial against a white paper and quickly look at the colour of the solution.

The specifications mandates that the solution should be clear, colourless and free from particulate matter. For some radiopharmaceutical solutions, a slight yellow colour in the preparation is also acceptable. Some radiopharmaceuticals are suspensions of particles or colloids.

3.4.4. Radioactive concentration

The aim is to determine the amount of radioactivity per volume of a radiopharmaceutical solution at a certain time. The method consists of the total radioactivity measured in a dose calibrator (double check that the radioisotope setting is correct) at a certain time point, and then the obtained radioactivity value is divided by the total volume of the solution.

The specification establishes that the regulatory agencies use the radioactive concentration at the end-of-synthesis time as a measure of radiopharmaceutical ‘strength’. Validation and stability studies should be carried out at the highest radioactive concentration that is intended to be used in the clinic in order to demonstrate ‘the worst-case possible’ effect of radiolysis on the stability of the radiopharmaceutical.

a A table of sodium chloride equivalents is available at: http://rxistsource.blogspot.co.uk/2012/12/table-of-sodium-chloride-equivalents.html

23 3.4.5. Endotoxin-content

The aim is to detect and/or quantify the presence of bacterial endotoxins (BET) originating from gram-negative bacteria. The method consists of: Gel-clot method or; chromogenic kinetic method with endotoxin testing system (B). Both methods make use of the reaction between BET and limulus amebocyte lysate (LAL), an extract of the horseshoe crab.

3.4.5.1.Gel-clot method The method is as follows:

Prepare the four different solutions A, B, C and D described below in test tubes;

 Incubate the reaction mixtures at 37 ± 1°C for 60 ± 2 minutes avoiding vibration;

 To test the integrity of the gel, take each tube in turn directly from the incubator and invert it through about 180° in one smooth motion;

 If a firm gel has formed the remains in place upon inversion, record the result as positive.

A result is negative if an intact gel is not formed. The test is considered valid when both replicates of solution B and C are positive, and when those of solution D are negative. Note that sensitivity of the labelled lysate and detection of interfering factors must be assayed to ensure the precision and the validity of the gel-clot test.

TABLE 1. SPECIFICATIONS OF TEST SOLUTIONS FOR ENDOTOXIN TEST

SOLUTION ENDOTOXIN CONCENTRATION / SOLUTION TO WHICH ENDOTOXIN IS ADDED

NUMBER OF REPLICATES

A None / Diluted sample solution 2

B 2× / Diluted sample solution 2

C 2× / Water for BET 2

D None / Water for BET 2

3.4.5.2.Chromogenic kinetic method with endotoxin testing system

The endotoxin testing system performs a duplicate endotoxin test of the sample and a positive control to comply with the regulatory requirements USP BET <85> and Ph. Eur. BET <2.6.14>.

The devise is measuring the amount of chromophore released from a chromogenic synthetic peptide by the reaction between endotoxins and the lysate. The analysis is usually performed on a cartridge preloaded with the reagents. The user is only required to add a specific volume of the sample to each well prior to perform the analysis. Testing for interferences and the optimal dilution factor is needed before to run endotoxin measurements on a radiopharmaceutical preparation.

The specification requires that the endotoxin limit for a radiopharmaceutical administered parenterally is specified in IU/mL or IU/V. The specification for the endotoxin-content may

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vary depending on the radiopharmaceutical (i.e. a typical value is ≤ 17.5 IU/mL or ≤ 175 IU/injection).