Nasal Spray Peptides Australia: Semax, Selank & PT-141 Research | Quantum Labs

Why intranasal delivery exists for peptides

Peptides are notoriously difficult to deliver outside of an injection. Stomach acid and gut proteases destroy most of them. Skin barriers block large polar molecules. The nasal cavity, by contrast, offers a thin, vascular mucosa that sits close to systemic circulation — and, for some molecules, a direct anatomical pathway into the central nervous system via olfactory and trigeminal nerve fibres.

That nose-to-brain pathway is the headline reason researchers have been interested in nasal peptide formulations for decades. Insulin, oxytocin, neuropeptides and short regulatory peptides have all been studied intranasally. A subset of those — Semax, Selank, PT-141, and others — have crossed into research-supplier catalogues because the nasal route is genuinely how the underlying studies dosed them.

This article walks through which peptides are commonly discussed in nasal-spray form, what the research actually shows about intranasal absorption, the formulation challenges, and the Australian regulatory picture for peptides sold or imported as nasal sprays.

Semax — the original nasal peptide

Semax is a synthetic heptapeptide derived from a fragment of adrenocorticotropic hormone (ACTH). It was developed in Russia in the 1980s and is the prototypical example of an intranasal neuropeptide. Russian clinical research has used Semax in the context of cognitive function and stroke recovery; Western preclinical literature focuses on its interactions with BDNF and the melanocortin system.

Semax is notable for being one of the few peptides where the intranasal route was the originally validated delivery pathway, not a workaround. Pharmacokinetic studies in rodents show measurable CNS penetration via the olfactory mucosa within minutes of intranasal administration.

Researchers in Australia who want to work with Semax typically purchase the lyophilised powder and reconstitute it into a saline-based solution that can be loaded into a dropper or research-grade nasal applicator. We don't sell finished nasal-spray products — we sell the raw peptide for in-vitro and laboratory use. The distinction matters from a TGA perspective and is covered later in this article.

Selank — Semax's anxiolytic cousin

Selank is another Russian-developed heptapeptide, this one derived from tuftsin (an immunomodulatory fragment of the IgG heavy chain). Its research profile is anxiolytic and immunomodulatory rather than nootropic — early studies put it alongside benzodiazepines as a comparator in animal anxiety models, with the headline finding that it produced anxiolytic-like effects without the sedation, dependence liability or motor impairment associated with GABAergic drugs.

Like Semax, Selank's preclinical and clinical pharmacology was developed around the intranasal route. Plasma and CSF concentrations after intranasal Selank in animal models peak within minutes and clear quickly — the short half-life is part of why the research literature dosed it on a repeated daily schedule rather than as a single bolus.

Selank is not a registered therapeutic good in Australia. It is supplied as a research peptide only, and the customer is responsible for ensuring their use case is consistent with their institutional or laboratory licence.

PT-141 (bremelanotide) — nasal vs injection

PT-141 has an interesting delivery history. Early clinical development of bremelanotide explored a nasal spray formulation, but the program ran into blood pressure spikes that were attributed in part to the high peak concentrations seen with the nasal route. The eventual approved product (in the US, under the brand name Vyleesi) used subcutaneous injection at a lower dose instead.

Some research-supply vendors still list PT-141 in nasal-spray form. The reason is partly historical (the original studies were intranasal), partly practical (some researchers prefer nasal dosing for ease of administration in self-experimentation contexts), and partly that subcutaneous injection isn't something every customer is willing or able to do.

From a research-comparison standpoint, the published literature on PT-141 includes both nasal and subcutaneous arms — so a researcher who chooses one route over the other can find prior work to inform their protocol. We supply PT-141 as lyophilised powder; reconstitution and delivery format are decisions the customer makes within their own research framework.

Melanotan nasal spray — why we don't list it

A significant share of nasal-spray peptide search interest in Australia is for Melanotan II nasal spray. We don't supply Melanotan II in any format, and the reason is simple: it is a prohibited substance under TGA Schedule 10. The fact that it is sometimes sold internationally as a nasal spray doesn't change its Australian status. We have a separate article on tanning peptides and the Melanotan family that covers the regulatory background in detail.

What the absorption research actually shows

The intranasal route is often described as if it were a one-size-fits-all way to get peptides into systemic circulation or the brain. The pharmacokinetic literature is more nuanced.

• Bioavailability is highly molecule-dependent. Small peptides (under ~1 kDa) with favourable charge and lipophilicity can achieve 10–50% systemic absorption intranasally. Larger or more polar peptides may sit in single-digit percentages.
• Formulation matters more than route. Plain saline solutions clear quickly via mucociliary action. Permeation enhancers, mucoadhesives, and pH buffering can shift absorption by an order of magnitude.
• Nose-to-brain transport is real but limited. The olfactory pathway represents a small fraction of the nasal mucosa surface; most intranasal absorption is actually systemic via respiratory mucosa.
• Reproducibility is a known issue. Head position, spray device, droplet size, and individual anatomy all influence how much of a dose reaches the absorbing surface versus running down the throat.

The implication for researchers is that "intranasal" is not a single delivery condition. A research protocol needs to specify formulation, device, volume per spray, and administration technique — and the published evidence base for a given peptide is only as strong as the formulations used in those original studies.

Reconstitution for intranasal research use

Lyophilised peptides are not nasal sprays. Reconstituting a peptide for laboratory intranasal use generally involves a sterile-filtered diluent (commonly bacteriostatic water or sterile saline for short-term research timelines), a known volume to achieve a defined concentration, and a research-grade applicator that can deliver a reproducible spray volume.

The reconstitution guide we publish for injectable research formats also covers the basics that apply to intranasal preparation — sterile technique, diluent selection, storage stability — though a researcher working with a nasal protocol would also need to think about applicator priming, sprayed volume calibration, and how long the reconstituted solution remains stable under their storage conditions.

Comparing routes — when nasal makes sense for research

For some peptides the intranasal route is the established research method (Semax, Selank). For others it's one of several published options (PT-141, oxytocin). For many others it has no published support and would be a speculative choice with no comparable studies to anchor dosing or interpretation.

A useful question for any researcher considering an intranasal protocol is: which route did the studies that generated the literature I'm relying on actually use? If the answer is intranasal, the dose-response and pharmacokinetic data translate. If the answer is subcutaneous or intravenous, switching to a nasal protocol means estimating bioavailability and effectively running a different experiment.

Regulatory framing in Australia

Peptides supplied for research use in Australia are not registered therapeutic goods. A research peptide sold as lyophilised powder for in-vitro and laboratory use sits outside the therapeutic goods framework. The moment a product is marketed as a finished nasal spray for human use, or labelled with therapeutic indications, it crosses into TGA jurisdiction.

That distinction is the reason we don't sell pre-made nasal sprays. Selling a lyophilised research peptide is a materially different activity from manufacturing and labelling a finished medicine. Research customers who want to use intranasal delivery in their own protocols can do so; we simply don't supply the finished dosage form. Our broader Australian peptide regulation overview covers the Schedule 4 / Schedule 10 / research-supply distinctions in more detail.

Where Quantum Labs fits

Our catalogue includes lyophilised research peptides that appear in the intranasal literature — including PT-141 and others where the published protocols span multiple routes. We don't sell Melanotan compounds, and we don't market finished nasal-spray products. The full catalogue is on our Australian research peptide directory page, and the broader compound education library is organised in the research peptide journal.