How does dosing work with 510k injection pens?
Nest 510k injection pens deliver .01mL or 1 insulin unit per partial turn of the pen dosage selector wheel. In informal terms, a partial turn is called a "click" as that's the noise the pen makes each time a new number is selected. That means that 1 click = 1 unit = .01mL.
Nest pens are based on the ISO 11608 design. This means they use standardized 3mL ISO 11608-3 style cartridges. That means a 3mL cartridge holds 3/.01mL or 300 units/clicks/.01mL.
To find the number of milligrams delivered, start with the total dosage in milligrams in the cartridge. For example for 4mg/3mL semaglutide, an extremely common dose used by 503B compounding pharmacies, the concentration would be 1.34mg/mL. Or multiply by .01mL (same as dividing by 100) to find the dosage per click or in this case .0134mg/click.
Common dosages can then be worked out backwards by dividing them by the dosage per click to find the number of clicks/units to dispense that dose.
0.25mg of semaglutide = 0.25mg/.0134mg/click = 18.65 clicks. Partial clicks can't be delivered, .01mL is the minimum dosing increment so round up to 19 clicks or 0.2546mg.
0.5mg of semaglutide = 0.5mg/.0134mg/click = 37.31 clicks, or round down to 37 clicks.
1mg of semaglutide = 1mg/.0134mg/click = 74.62 clicks or round up to 75 clicks.
Of course different drugs will have different compounded strengths. Be sure when choosing a pen to choose concentration where the cartridge will be used faster than 56 days/8 weeks after puncturing. In the example above 4mg/3mL would deliver 8 weeks of 0.25mg which is the limit for risking contamination from an opened container.
