Background and Importance Oral administration of injectables is an alternative for patients with difficulties tolerating solid pharmaceutical forms.

Due to their physicochemical characteristics not adapted to oral administration, gastrointestinal adverse effects can occur, especially in patients with transpyloric feeding tube, especially when they have an osmolarity >500 mOsm/L or pH <3.5.

Aim and Objectives The aim of the present work is to characterise the physicochemical properties of injectable formulations commonly used orally and their gastrointestinal absorption site in order to increase safety in their administration by transpyloric feeding tube.

Material and Methods A literature search was conducted to establish the gastrointestinal absorption site of the active principles (AP) analysed.

For each preparation, pH and osmolality were experimentally determined. The pH was measured with a pH meter (Crison 2006, Hach Lange España, S.L.U., Spain). Osmolarity was determined using the Fiske Model 210 Micro Osmometer (John Morris Scientific Pty Ltd., Australia), considering the density of the active principles studied to be equal to 1 mg/ml. All measurements were performed in triplicate.

Results Of the 24 APs analysed, pH values<3.5 were found in 21% of preparations, which discourages transyejunal administration. In addition, 25% of the formulas administered had osmolarity >500 mOsm/L.

• Of the 13 APs that have bioavailability by transpyloric route, only eight are adequately formulated for this, and another three could be diluted prior to administration to avoid high osmolarities.

• Of the five APs that cannot be administered via the transpyloric route, three of them are also not adequately formulated.

• Of the remaining six APs, whose absorption site cannot be objectified, three have good physicochemical characteristics and with another two this could be achieved by diluting with water.

Conclusion and Relevance Most of APs studied, the gastrointestinal absorption of the drug is not sufficiently characterised, leading to uncertainty when administered by transpyloric feeding tube.

Many of the injectables have a high osmolarity and therefore require prior dilution, while the pH values of some of them can be an added factor for the development of digestive intolerances.

Conflict of Interest No conflict of interest.