Now, microscopic needles for painless drug delivery

February 5th, 2008 - 1:47 pm ICT by admin  

Washington , Feb 5 (ANI): In a first of its kind study on human subjects, researchers at the University Of Kentucky College Of Pharmacy and the Georgia Institute of Technology have shown that patches with microscopic needles on one side can help in the transdermal administration of an important drug that cannot normally pass through the skin.

The study could be useful in promoting the use of microneedles as a painless method for delivering drugs, proteins, DNA and vaccines into the body. In addition, microneedles also aid through an ability to produce therapeutic drug levels with lower doses, and lowered production of metabolites that may cause side-effects.

Though transdermal drug delivery is a step ahead of other drug delivery techniques having various advantages in pain management, congestive heart failure and hormone replacement, the other systems can only be used for a very few number of compounds that easily pass through the skin.

As microneedles can painlessly punch microscopic holes in the outer layer of skin known as the stratum corneum, they can be useful in expanding the range of drugs and vaccines that can be delivered transdermally. Earlier studies in this field involved drug delivery in animals and on human cadaver skin.

The study was led by David Hudson, a graduate student in the UK College of Pharmacy Department of Pharmaceutical Sciences, fellow in the UK College of Medicine’s Department of Psychiatry, and colleagues who set out to find if microneedle patches could actually help in delivering useful amounts of drug compounds that otherwise couldnt pass through the skin.

The researchers used the drug naltrexone, a skin-impermeable compound that is used to treat opiate and alcohol addiction, as a test compound.

While working with a small group of non-addicted human test subjects, firstly, the researchers prepared a section of skin on each subjects arm by pressing and removing thumb-sized patches that contained 50 stainless steel microneedles each about 620 microns about 1/40th of an inch in length. Later they applied a gel containing naltrexone to the prepared area, which was then covered by a protective dressing.

They kept a watch on the concentration of the drug in each subjects bloodstream for 72 hours. They immediately saw that the levels of the drug had reached the pharmacologically active concentrations, and those levels remained steady for at least 48 hours in the six test subjects.

However, when similar treatment was given to the control subjects without the microneedle preparation prior to application of the naltrexone gel, it was found that none of them had detectable levels of the drug in their bloodstream.

The researchers also did electrical resistance testing of the skin on separate subjects to find out how long the pores created by the microneedles remained open. This indicated that the drug could pass through treated skin for at least 48 hours before natural healing processes closed up the pores.

Despite maintaining a steady level of the naltrexone, microneedle has one more advantage over oral administration: a reduction in the presence of compounds metabolized from the drug. The primary metabolite, known as naltrexol, which is produced by the liver and intestines when the drug is administered, it results in many side-effects, which can be avoided by transdermal administration of naltrexone, through microneedles.

Microneedle administration also reduced the amount of drug required to produce therapeutic levels, replacing a 50 milligram tablet with 10-12 milligrams of drug in the gel. Its use also produced steady bloodstream levels of the drug, without the initial peak that occurs with oral delivery.

The study has been reported in the journal Proceedings of the National Academy of Sciences. (ANI)

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