A needle which is submillimeter in size is also effective because the primary task of drug delivery is on the topmost layer of the skin called stratum corneum. Keeping this in mind micro millimeter sized needles is developed and the drugs are delivered. These size needles are developed to penetrate on the skin without a trace, that is, little or no pain at all. This is demonstrated in diabetic animal models. To produce this kind of small sized needles, novel microfabrication method is adapted by the microelectronics industry using inexpensive and suitable methods for huge production.

A recent study has also found that microneedles are painless and it is also found out that geometric parameter is the cause of pain. However smaller needles are not acceptable in all the cases because large volumes of drugs and large particulates require large size needles. If the needle is also small in size, it cannot penetrate deep into the tissues and microneedles are just designed to deliver drugs on the skin. The dimension a skin surface is also another factor worth considering and micro needles cannot be used here and therefore special insertion devices are used.

There are also some other needle free alternatives such as jet injectors. They are used to accelerate liquid droplets with a high velocity over the skin and are used to administer vaccine, insulin and other drugs but they also cause pain and injury. To passively deliver drugs across the skin, transdermal patches are used but are limited to hydrophobic and smaller molecules.

Smaller needles can reduce pain such as 33 or 31 gauge needles but are not suitable for all applications. It is best to choose wisely.

Pain and Needle Insertion - Part II