Nasal Delivery Research: How Studies Establish Exposure and Effect

Start with the endpoint, not the route label

Calling an experiment “intranasal” identifies where a preparation was administered. It does not tell us how much intact compound entered the circulation, whether it reached a particular tissue or whether a measured response improved health.

A useful assessment separates four questions: was the preparation deposited as intended; was exposure measured; did a biological response occur; and was there a meaningful clinical outcome? A study may answer one of these well while leaving the others unresolved. The endpoint determines the conclusion the experiment can support.

Semax: what a connectivity study actually tested

The 2018 Semax imaging study included 24 healthy volunteers, with a reported age of 43.9 ± 9.5 years. Fourteen received intranasal 1% Semax and ten received placebo. Functional MRI was performed before administration and at five and twenty minutes afterwards.

The research question concerned resting-state brain networks, including the default mode network. Resting-state connectivity describes statistical relationships between fluctuations in imaging signals across brain regions. A change in those relationships is a neuroimaging finding; it is not itself a score for memory, attention or everyday functioning.

The pre-administration scan provides a baseline, and the placebo group helps assess changes that might occur without Semax. However, the small groups and brief observation window limit broader interpretation. The experiment does not establish durable cognitive efficacy, quantify nasal bioavailability or show where intact Semax travelled.

This illustrates a general reporting rule: retain the measured endpoint in the conclusion. “Altered connectivity” should not become “improved cognition,” and an imaging response should not become a numerical claim about brain delivery.

Exposure measurements answer a separate question

Pharmacokinetics examines exposure over time, commonly through measured concentrations in blood. Pharmacodynamics examines a response to the compound. Combining them can help relate exposure to effect, but neither automatically supplies a patient-relevant benefit.

The intranasal PT-141 study by Diamond and colleagues measured blood exposure and pharmacodynamic outcomes in men under placebo-controlled conditions. Its importance for delivery research is that exposure was investigated directly, rather than inferred solely from a downstream signal. Those findings remain specific to the experimental preparation; they cannot certify another formulation’s concentration, pump performance or long-term outcomes.

A different design can help examine competing pathways. In the nasal-versus-intravenous oxytocin study, some regional brain-perfusion changes tracked circulating oxytocin, while other nasal-associated changes were consistent with an additional nose-to-brain contribution. Differences between nasal devices also mattered. An intravenous comparator helps test a systemic explanation, but perfusion imaging still does not measure intact peptide at a brain target.

Endocrine responses need anatomical restraint

Hormone release is a measurable biological response, but it does not uniquely identify how a nasal preparation generated that response. Endocrine pathways can amplify signals originating outside the brain.

The 2025 kisspeptin-54 investigation used a randomised, double-blind, placebo-controlled crossover design and found stimulation of gonadotropin release in healthy participants and women with hypothalamic amenorrhoea. Crossover comparisons allow participants to contribute observations under different study conditions, reducing some between-person variability. Complementary mouse experiments implicated olfactory-system signalling; that mechanistic evidence should remain distinct from the human hormone measurements.

Similarly, a controlled human study of intranasal GHRH(1–44) reported growth-hormone responses. It does not establish nasal performance for other secretagogues. The human ipamorelin PK/PD study used a 15-minute intravenous infusion in healthy men, whereas the nasal ipamorelin absorption investigation involved rats. Species, route and sequence cannot be exchanged merely because the studies concern growth hormone. Neither paper demonstrates clinical efficacy or compatibility of a CJC–ipamorelin premix.

Clinical scales and animal signals belong in different columns

The 2008 Selank study compared 30 Selank-treated patients with 32 receiving medazepam among people with generalised anxiety disorder and neurasthenia. Rating scales address symptoms more directly than resting-state connectivity, but this comparison is not modern proof of equivalence and should not be represented as a blinded placebo-controlled trial. Its abstract also does not establish a route suitable for making nasal-exposure claims.

For preclinical work, the model must stay visible. Epitalon research in rat neocortex measured neuronal activity after intranasal administration. Nasal NAD research published in 2026 investigated cells and mice. These studies can inform hypotheses, but neither supplies human pharmacokinetics for a finished product. NAD+ is not a peptide, and its results cannot serve as a general nasal-peptide validation.

What would make a delivery claim testable?

A meaningful claim specifies the molecular identity, preparation, device, population and intended endpoint. Exposure assessment should distinguish intact compound from a nonspecific downstream signal. Comparisons must also address whether a response could arise through systemic circulation rather than a proposed direct neural pathway.

Device characterisation is a separate requirement. Declared bottle content divided by a stated spray count gives a nominal quantity, not independently measured output or absorption. Pump state, changing fill and residual volume can affect delivery. The EMA pharmaceutical-quality guideline for inhalation and nasal products is relevant methodological context, not proof of a research preparation’s clinical performance.

The formulation guide addresses vehicle, container and stability measurements, while the nasal-label guide explains nominal quantities. Taken together, these distinctions prevent a common error: using evidence for one link in the delivery chain as though the entire chain had been demonstrated.