Testing a Nasal Formulation: What a Stability Claim Must Measure

Start with a claim that can be evaluated

“Stable at room temperature” leaves important experimental questions unanswered. Which temperature range, for how long, in which container—and before or after repeated actuation? A stability assessment needs a defined claim before its results can support one.

The ICH Q1A(R2) guideline provides context for stability-study design. Its principles do not supply missing results for a research product. Refrigerated observations and brief transport excursions answer different questions from long-term room-temperature storage.

Use the kisspeptin study as a boundary-setting example

Mills and colleagues’ 2025 intranasal kisspeptin-54 paper evaluated the study solution in specified containers at 4°C over 60 days. This formulation component matters independently of the paper’s human administration component: interpreting an exposure experiment requires understanding the material being investigated.

The storage evidence remains specific to that solution and those conditions. It cannot establish another peptide’s shelf life, performance in a different pump or stability during repeated room-temperature use. The experimental lesson is to match the proposed claim to the actual preparation, container and observation window—not to borrow a duration from a related paper.

Separate endpoints rather than averaging them into “quality”

A content assay asks how much analyte remains. A stability-indicating analytical method must distinguish the target from relevant degradation products. Physical observations assess changes such as precipitation, but an unchanged appearance cannot exclude chemical loss.

Chromatographic area percentage depends on the method and detected components; it is not automatically a measure of mass content, identity, sterility or endotoxin. Microbial quality and preservative effectiveness require their own assessments. Delivery testing adds another endpoint: whether the container–pump system continues to perform as specified.

The EMA nasal and inhalation product quality guideline is contextual guidance for these distinctions, not confirmation of PeptaGen product performance.

Treat the preservative as a variable, not a result

PeptaGen’s manufacturer-supplied formulation description identifies m-cresol, or metacresol, while keeping the full composition and proportions confidential. Disclosure of that ingredient does not independently establish its concentration, antimicrobial performance or compatibility with the peptide.

Heljo et al.’s peptide–preservative research shows why those interactions warrant investigation: a preservative can influence peptide self-association. Its antimicrobial role therefore cannot substitute for chemical-stability evidence from the complete formulation.

What a useful evidence summary should contain

Readers should be able to identify the tested batches, packaging, conditions, time points, methods and acceptance criteria, including whether in-use bottles were assessed. Reporting these features need not disclose proprietary proportions.

Such a summary supports only the endpoints actually measured. It does not establish absorption or biological efficacy. Those require compound- and route-specific exposure studies, discussed separately in the nasal delivery mechanism guide.