Oromucosal Administration of Oxytocin: The Development of 'Oxipops'

The role of the hypothalamic neuropeptide oxytocin in influencing the brain and behavior has been the subject of widespread research over the last few decades due, most notably, to its reported involvement in promoting social cognition and motivation, reducing anxiety, and relieving pain. It is also increasingly being considered as an important therapeutic intervention in a variety of disorders with social dysfunction as a symptom. While, in recent years, studies in humans have administered oxytocin primarily via an intranasal route, since it may partly enter the brain directly this way via the olfactory and trigeminal nerves, there is increasing evidence that many of its functional effects can be peripherally mediated via increasing its concentration in the blood. This has opened up an oromucosal administration route as an alternative, which is beneficial since the oral consumption of peptides is problematic due to their rapid breakdown in the acidic environment of the gastrointestinal system. In this review we will discuss both the methodologies we have developed for administering oxytocin via lingual application and medicated lollipops, 'oxipops', in terms of increasing blood concentrations and the bioavailability of the peptide, and also their validation in terms of functional effects on the brain and behavior. While areas under the curve are significantly greater in terms of plasma oxytocin concentrations following intranasally relative to oromucosally administered oxytocin, with the estimated absolute bioavailability of the latter being around 4.4% compared with 11.1% for intranasal administration, the time to peak concentrations (around 30 min) and functional effects on the brain and behavior are broadly similar. We will also discuss potential therapeutic advantages of the oromucosal administration of oxytocin in different clinical contexts and its wider application for other peptides which are increasingly being developed for therapeutic use.