Friday, 1 July 2011

When drugs and ink research collide....

Sometimes when you study inkjets and drugs or write about them (in the case of my previous posts ) you might be surprised that these two could come together to some sort of monster baby of cosmic proportions.  Well maybe not cosmic proportions but interesting ones nonetheless.  So when I saw this recently published article by Buanz et. al I was amazed at this stunning coincidence. 

This group wanted to 'evaluate the use of thermal ink-jetting as a method for dosing drugs onto oral films.' They replaced a regular Hewlett-Packard printer cartridge with a modified one so that an aqueous drug called salbutamol sulphate replaced the ink.  Buanz et al. wanted to find a better solution for personalized dosing.  'Personalized dosing cases where delivery of a precise dose is paramount, such as for highly potent actives,
drugs with a narrow therapeutic index, or paediatric formulations (where the dose is based on body mass), the individual dosage unit may need to be divided prior to administration.' A printer with thermoinjetting is something that is readily available and most likely easy to use.  The authors used
salbutamol sulphate an important drug for anyone suffering from asthma as it is a  is a short-acting β2-adrenergic receptor agonist used for the relief of bronchospasm.  They probably chose salbutamol because of its wettability properties and because it might be a drug where they have to vary the dose on the person.  

So what did they find?  They found that the viscoscity was important in this case for ink jet printing with  viscosities between 1.1 and 1.5 mm2 s-1 were found to be found optimal.  The surface tension was not as important but a minimum surface tension needed to jet satisfactorily is 35 mN m−1.  Aqueous ink has a
surface tension of 55 mN m−1.
  The solutions used in this  work had surface tensions from 46 to 71 mN m−1 so these had to be maintained to be within in jettability range.  They used the Kibron Delta-8 to maintain this surface tension above 35 mN m-1.   

In their experiment they used paper and a later a film made of potatoe starch.  Possibly the surface tension might need to be more strictly controlled if they use other solvents in the solution, or want to very accurate in the dosage and size of the tablet or if the drug is printed on other materials.  In any case they found: 'thermal injet printing offers a rapid method for extemporaneous preparation of personalized-dose medicines.'

P.S. I wonder if they got some of the ideas of inkjet printing from the people making acid blotter paper like the picture above.  Different technique used in this case however.