Reconstitution math on Selank: getting it right

A reader on r/Peptides recently asked a version of a question I get constantly: they had already reconstituted Selank with bacteriostatic water for a nasal spray, then went back and wondered if that was a mistake. Short answer on selank reconstitution math: the arithmetic for figuring out your concentration is the same no matter what diluent you use, and the diluent choice itself is where people actually go wrong for a nasal spray.

Let me walk through both pieces, because they get tangled together in most of the threads I read.

The actual math, step by step

Selank almost always ships as a lyophilized powder in a vial, labeled in milligrams. Reconstitution math is one division and one multiplication, and it does not change based on what liquid you use.

Say you have a 10 mg vial. You add 5 mL of diluent. That gives you 2 mg per mL, or 2,000 mcg per mL. A standard metered-dose nasal sprayer puts out roughly 0.1 mL per actuation (check your specific sprayer, they vary), which means each spray delivers about 200 mcg. One spray in each nostril gets you to 400 mcg, which lands right in the range most people run.

If you want a lower per-spray dose, add more diluent. The same 10 mg vial in 10 mL of liquid gives you 1 mg per mL, or 100 mcg per spray at that same 0.1 mL actuation volume. If you want a higher dose per spray, use less diluent. The formula is: (mg of peptide ÷ mL of diluent) × mL per spray = mcg per spray. That is the entire calculation, and it is identical whether you use bacteriostatic water or saline.

Where I see people trip up is assuming their sprayer puts out exactly 0.1 mL when it does not. Cheap aftermarket sprayers from Amazon vary. If precision matters to you, actuate a few sprays into a small graduated container and check the actual volume before you commit to a dosing plan.

Why the diluent matters more than the formula

This is the part the Reddit thread was really asking about, and it is a fair question. Bacteriostatic water contains 0.9% benzyl alcohol as a preservative. For an injectable preparation, that is exactly what you want: the alcohol keeps the vial sterile across a month or more of repeated draws, and the tiny amount that goes in subcutaneously is a non-issue.

For a nasal spray you are using daily, that same benzyl alcohol is a problem. Nasal mucosa is thinner and more reactive than skin or muscle tissue, and repeated exposure to the preservative can cause irritation, dryness, and in some people ongoing discomfort that has nothing to do with the peptide itself. I have had people tell me they assumed a burning sensation from their Selank spray meant the peptide was "too strong," when what was actually happening was the benzyl alcohol doing what benzyl alcohol does to mucous membranes over repeated daily contact.

Sterile saline, or 0.9% sodium chloride irrigation solution, is chemically much closer to what your nasal tissue is used to. It carries no preservative, which is the trade-off: your reconstituted bottle needs to stay refrigerated and gets used up faster, typically within one to two weeks instead of the 28-plus days you get from a BAC water vial. For anyone using Selank on an occasional or as-needed basis, that shorter shelf life is a real inconvenience and BAC water is a reasonable choice. For anyone running it daily as an ongoing protocol, which is most of the people asking this question, saline is worth the extra fridge trips.

What the human trials actually used, and why route matters here

It is worth knowing that every published Selank clinical trial used the intranasal route. Selank is approved in Russia for generalized anxiety disorder specifically as a nasal spray, and that clinical record includes a head-to-head comparison against medazepam, a benzodiazepine, where Selank matched the anxiolytic effect with a better side-effect profile. A follow-up trial combining Selank with phenazepam found it reduced benzodiazepine side effects while holding onto the anxiolytic benefit. Both of those trials, and the broader Russian evidence base, used intranasal dosing. That is one more reason to get the nasal-spray mechanics right rather than treating it as an afterthought.

Part of why the route matters mechanistically comes down to what receptors Selank engages depending on how it enters your body. Animal work has shown Selank inhibits the enzyme that breaks down your body's own enkephalins, stabilizing endogenous opioid tone rather than flooding the system with an exogenous compound, a mechanism confirmed in both human and animal tissue. There is also a documented dopaminergic component to how Selank normalizes mood in animal models of anxiety, which helps explain why the anxiolytic effect does not come with the flat, blunted feeling some people get on SSRIs. None of that changes the reconstitution formula, but it is the reason getting the delivery method right, not just the concentration, actually matters for whether you feel the effect you are looking for.

Getting the vial-to-spray ratio right in practice

My own preference, and what I have landed on after going back and forth on this with a fair number of people who use Selank daily, is a 10 mg vial into 5 mL of sterile saline for anyone running it as a daily anxiety or focus protocol. That gives you 200 mcg per spray, clean round numbers, and one or two sprays gets most people into their effective range without doing mental math every morning.

If you are only using Selank occasionally, say before a stressful event or a deep-work session, bacteriostatic water is a defensible choice because the exposure is brief and infrequent enough that the benzyl alcohol issue barely comes up. Match the diluent to how often the bottle is actually going to be in your nose.

One practical step that gets skipped constantly: generic metered-dose nasal sprayers bought separately are not sterile out of the box. Boil the sprayer top briefly before your first use. It takes two minutes and it is the difference between introducing contaminants into an otherwise clean peptide solution and not.

Standard daily dose across the practitioner community runs 300 to 600 mcg per day, split into two or three administrations, which at 200 mcg per spray works out to one to three sprays across the day. The doses and schedules here are for educational and informational purposes only. These peptides are sold for research use only and are not FDA-approved drugs. This is not medical advice. Consult a qualified physician before beginning any protocol.

I see this exact reconstitution confusion constantly with people newer to peptides generally, not just Selank. It is worth reading through the aliquoting and freeze-thaw guidance if you are also managing multiple vials, since a lot of the same storage-life logic applies once you start splitting reconstituted peptide across containers.