Hydrophobic ion pairing: Key to highly payloaded self-emulsifying peptide drug delivery systems

•Independent from the type of peptide, docusate showed the most efficient hydrophobic ion pairing properties and was revealed as universal counter ion.•Novel SEDDS containing Capryol 90, Labrafil M 2125 CS, Labrasol ALF, Peceol, propylene glycol, tetraglycol, Transcutol HP and Tween 20 were developed.•The complexes were incorporated into SEDDS achieving a payload over 10%.•SEDDS exhibited high stability and constant negative zeta potential over a 4h incubation time.•Correlation between the type of lipid excipients and the solubility was detected.