Selank and Semax Intranasal Dose — Volume Planner

Published 2026-08-18 · Lyophile Editorial

Bacteriostatic water volume for 5 mg Selank or Semax vials

Use 2 mL of bacteriostatic water per 5 mg vial → 2500 mcg/mL stock → 25 mcg per unit on a U-100 insulin syringe.

| Diluent | Concentration | mcg per 0.01 mL (1 unit) | mcg per 0.1 mL (10 units) | |---|---|---|---| | 1 mL | 5000 mcg/mL | 50 mcg | 500 mcg | | 2 mL | 2500 mcg/mL | 25 mcg | 250 mcg | | 3 mL | 1667 mcg/mL | 16.7 mcg | 167 mcg | | 4 mL | 1250 mcg/mL | 12.5 mcg | 125 mcg |

The math:

• 5000 mcg ÷ 2 mL = 2500 mcg/mL
• 2500 mcg/mL ÷ 100 units/mL = 25 mcg per unit
• 10 units = 250 mcg

A 5 mg lyophilized vial has roughly 0.5 mL of powder plus excipients. Adding 2 mL diluent gives a final volume of approximately 2.3–2.5 mL after displacement — factor this into spray-count estimates.

How to reconstitute:

1. Inject 2 mL bacteriostatic water into the vial, aiming down the side wall.
2. Swirl gently — do not shake.
3. Let it sit 5–10 minutes until fully dissolved.
4. Draw your dose using a U-100 insulin syringe (each tick = 0.01 mL).

Nasal spray output per actuation

A standard nasal spray pump delivers 0.1 mL per actuation → 250 mcg per spray from a 2 mL reconstitution.

| Diluent Volume | Concentration | mcg per 0.1 mL spray | mcg per 0.05 mL spray | Usable sprays (0.1 mL pump) | |---|---|---|---|---| | 1 mL | 5000 mcg/mL | 500 mcg | 250 mcg | ~8–10 | | 2 mL | 2500 mcg/mL | 250 mcg | 125 mcg | ~18–20 | | 3 mL | 1667 mcg/mL | 167 mcg | 83 mcg | ~28–30 | | 4 mL | 1250 mcg/mL | 125 mcg | 62.5 mcg | ~38–40 |

The failure mode: people calculate 20 sprays from 2 mL, then get 16 usable actuations because they didn't account for the 2–4 sprays needed to prime the pump and residual volume that won't aspirate. If you need 30 doses, reconstitute with more diluent or plan for a second vial.

Check your pump spec sheet — some metered pumps deliver 0.05 mL or 0.14 mL per actuation. A 0.1 mL pump gives approximately 20–25 sprays from a 2 mL fill, minus 0.2–0.4 mL lost to priming and dead volume.

Selank vs Semax — volume math differences

Both are heptapeptides, but typical research dosing differs: Selank at 250–750 mcg, Semax at 400–800 mcg per administration. That changes how many actuations you need per dose.

With 2 mL reconstitution (250 mcg per 0.1 mL spray):

| Peptide | Dose range | mcg per spray | Sprays per dose | Usable sprays per vial | |---|---|---|---|---| | Selank | 250–750 mcg | 250 mcg | 1–3 | ~18–20 | | Semax | 400–800 mcg | 250 mcg | 2–4 | ~18–20 |

If you want fewer actuations per dose for Semax:

• Reconstitute with 1.5 mL → 3333 mcg/mL → 333 mcg per 0.1 mL spray
• 500 mcg = 1.5 sprays; 800 mcg = 2.5 sprays

If you want finer dose control for Selank:

• Reconstitute with 3 mL → 1667 mcg/mL → 167 mcg per 0.1 mL spray
• 250 mcg = 1.5 sprays; 500 mcg = 3 sprays

Neither approach is wrong — match concentration to your target dose per actuation.

Measuring 0.1 mL without a spray bottle

Use a U-100 insulin syringe: 10 units = 0.1 mL. Each unit mark = 0.01 mL.

| Volume | U-100 units | |---|---| | 0.05 mL | 5 units | | 0.1 mL | 10 units | | 0.2 mL | 20 units | | 0.5 mL | 50 units |

The common error: people use a 1 mL tuberculin syringe and try to eyeball 0.1 mL. The graduations are 0.01 mL apart but tightly spaced and easy to misread. An insulin syringe has clearly separated unit marks that are easier to read accurately.

Intranasal administration without a spray bottle:

1. Draw your dose into the insulin syringe.
2. Remove the needle.
3. Tilt head back.
4. Express liquid into one nostril.

This delivers the same volume as a spray but without atomization — absorption may differ, which is a research variable to control for.

Note on syringe dead volume: U-100 insulin syringes have a dead volume of 1–2 units (0.01–0.02 mL) that you'll lose when transferring between containers.

Shelf life of reconstituted Selank or Semax

Reconstituted peptides in bacteriostatic water: 2–4 weeks refrigerated at 2–8°C.

Bacteriostatic water contains 0.9% benzyl alcohol as a preservative, which inhibits bacterial growth but does not prevent peptide degradation over time. USP <797> standards recommend beyond-use dates of 28 days for refrigerated, preserved preparations — that's the practical ceiling.

Key limitations:

• Benzyl alcohol is bacteriostatic, not bactericidal — it slows growth but doesn't kill everything.
• Repeated needle punctures introduce contamination risk.
• If the solution turns cloudy or develops particulate matter, discard it regardless of the date.

Lyophilized peptide in the original vial is stable for months to years when kept desiccated and away from light. The clock starts when you add diluent.

Multi-vial dosing schedule planner

Formula: (daily mcg × days of use) ÷ 5000 mcg per vial = minimum vials. Add one extra vial for priming loss, dead volume, and measurement error.

Example: 500 mcg/day × 20 days = 10,000 mcg = 2 vials. With 20% loss to dead volume and priming, plan for 3 vials.

| Daily Dose | 10 Days | 20 Days | 30 Days | |---|---|---|---| | 250 mcg | 1 vial | 1 vial | 2 vials | | 500 mcg | 1 vial | 2 vials | 3 vials | | 750 mcg | 2 vials | 3 vials | 5 vials |

Table assumes 5 mg vials and 80% usable yield. Adjust if your metered pump has known dead volume.

Sourcing

Bacteriostatic water:

• BAC Water Depot — sterile 0.9% benzyl alcohol water, multi-dose vials
• Amazon — various suppliers, check for USP-grade labeling
• Medical supply retailers — hospital-grade options, often in larger volumes

Research peptides:

• Alpha Amino USA — per-lot HPLC/MS COA, US-shipped
• Peptide Sciences — published third-party testing, US-based
• Limitless Life Nootropics — domestic shipping, COA available on request

For research use only — not clinical guidance. Always verify your calculations and equipment before use. The math in this article is based on published manufacturer specifications and standard laboratory practice, not on independent testing or clinical validation.