Background Most drugs are available only as solid oral dosage forms. Patients with swallowing difficulties supplied by enteral nutrition (EN) are not able to consume these pharmaceutical forms. Therefore, to improve the management of their drug therapy, it is often necessary to handle original drug to prepare an extemporaneous liquid dosage form.
Purpose The aim of this work was to perform a gravimetric and spectrophotometric quantification of different extemporaneous preparations (prepared starting from dissolved and crushed tablets) containing pravastatin sodium salt (PraNa) that are administered through a feeding tube for EN. Results were compared with a PraNa standard solution.
Material and methods Solution A was prepared choosing standard PraNa, parabens and sodium bicarbonate 8.4% solution. Solution B was obtained using 20 mg PraNa tablets (Pensa SpA), parabens and sodium bicarbonate 8.4% solution. Solution C was prepared crushing tablets of PraNa in a mortar and then the obtained powder was dispersed with water. Final concentration in all 3 preparations was always 4 mg/mL.
10 mL of each solution were administered through an enteral syringe into the feeding tube and then collected downstream of the tube. After each administration, the tube was flushed with distilled water (10 mL). The total volume, weight and absorbance (238 nm) were measured to determine the drug concentration and amount delivered through the tube. Statistical analysis (t test or Anova) was performed to evaluate the obtained results.
Results Gravimetric results about the upstream delivered weights of each different preparation were 20.52 ± 0.093 mg, 21.41 ± 0.060 mg and 19.96 ± 0.270 mg; instead, the collected quantities from the distal point of the tube were 18.92 ± 0.261 mg, 19.63 ± 0.151 mg and 18.71 ± 0.449 mg, respectively. Spectrophotometric quantifications provided these values: 41.92 ± 1.08 mg delivered by whole tablets versus 40.98 ± 0.270 mg, 43.79 ± 1.94 mg and 42.83 ± 1.69 mg delivered downstream by the 3 preparations, respectively.
The t test (p < 0.005) revealed significant differences among the values obtained with the gravimetric method, but there were no significant differences in the amount of administered drug as quantified through spectrophotometer measurements. No differences were found among the drugs administered using the different preparation methods when tested with Anova.
Conclusion Comparing the different preparation methods, significant differences were found only when gravimetric determination was used. Instead, spectrophotometric determination gave results in agreement with the real amount of administered drug.
No conflict of interest.
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