Punch sticking is the adherence of powder to the tooling surface. It occurs when granules attach themselves to the faces of the tablet punches, instead of locking together to create a uniform tablet. Sticking can happen at any time during production of a batch. It can be reduced by increasing the adherence of the active pharmaceutical ingredient to the ingredient, or by decreasing the interaction between the active pharmaceutical ingredient and the punch.
Punch sticking can be reduced by reduction of the adherence of the API to the punch.
- Use excipients with higher tabletability to increase the API-excipient interaction
- Increase efficiency of lubrication (type, amount, mixing)
- Add flow-aid or anti-adherent (e.g. silica, talc)
- Reduce API surface area by increasing PSD, if dissolution allows
- Optimise punch design; e.g. reduce embossing, polish/coat punches, different type of steel
- Optimise pre-compression and compression pressure
- Increase dwell time
- Reduce humidity and moisture in formulation
- Reduce heat of compression for low temperature melting material (API)
- Use filler-binders with lower surface area, lower electrostatics and lower hygroscopicity (e.g. lactose generally has lower punch sticking propensity than mannitol)