Attachment Experience From Weeks I & II

Greetings to all! Hope all is good there!


My attachment had started off with quite a bang since day 1 last week, the very day I was given the objectives and scope of my major project(MP). You'd find out why as you go along.


Basically, I've been posted to nowhere unfamiliar - back to TP - for my first ten weeks of attachment. But during the entire duration there, I'd be focusing on just my MP only. In other words, you shouldn't be expecting much of any routine lab work but more of some jucier bits (I hope). Also, my MP's been snatched out from an area pretty much alien to our BMT option; it'd probably would fit more nicely under the subject title of Pharmaceutical Analysis (In other words, that's pretty good for me, as in think resume and you'd know why, hahs). And as with every new experience, I'm really hoping to grab more than just a thing or two out of it into my bag of knowledge.


Well, to start off proper, the MP's got to do with an antihyperglycemic drug called metformin, alongside an impressive masterpiece - High Performance Liquid Chromatography (HPLC). The gist of it is to come up with a method development and method validation to quantitate an extemporaneous form of metformin and test for its stability with the help of the trusty HPLC.


In case you might be scratching your head about metformin, again, it is an antihyperglycemic agent commonly used to treat patients with type II diabetes. It is believed to bring about its mode of action through three ways:
i. Decreasing gluconeogenesis in the liver
ii. Enhancing insulin senstitivity by increasing peripheral glucose uptake and utilization
iii. Decreasing intestinal absorption of glucose




Also, metformin has the chemical formula of C4H11N5. HCL when in generally all dosage forms, and would be described as strongly basic and polar, freely soluble in water, soluble in methanol, slightly soluble in ethanol, and practically insoluble in methlyene chloride, acetone, chloroform and ether. Unlike many other antiglycemic drugs such as that of sulfonylureas however, metformin generally does not cause hypoglycemia or hyperinsulinaemia. Nonetheless, as is inevitable with all drugs, metformin can bring about certain unwanted side effects such as nausea, stomach upset, diarrhea and even lactic acidosis in serious cases.

At present, metformin is only available in two types of dosage forms – the first being a more commonly prescribed tablet while the other is a relatively new liquid solution. However, despite the breakthrough of the relatively new liquid metformin solution, the problem regarding difficulty in swallowing of the drug in its tablet dosage form, often due to dysphagia, by a significant fraction of patients with type II diabetes - the elderly, still persists worldwide. This is so as the liquid solution of the drug, Riomet® produced by Ranbaxy Laboratories, is only available only in the U.S and not other countries, such as that of Singapore. Moreover, the disease is increasing in prevalence among the children population too, another group of patients who would have to share in the agonising task of swallowing a tablet due to their relatively poor coordination of muscles required in swallowing. On top of these difficulties, it should be noted that the treatment lasts for the rest of an individual's lifetime - an arduous burden to carry especially with the abovementioned difficulties.

This project, in relation to the developement of a new dosage form of metformin, hopes to develop a simple and efficient method for the quantitation and stability testing on an extemporaneously prepared metformin solution formulation with the help of HPLC. This in turn would allow for the determination of metformin concentration and stability in future newly-developed metformin solution formulations.

With some light shed onto the scope of the project, let's move on to some technical aspects shall we, whereby with technical aspect, I mean nothing else other than HPLC.

As the name suggests, HPLC is a type of chromatography, or a technique for the separation of mixtures of compounds in a sample. This separation takes place between a mobile phase -otherwise known as the solvent, and a stationary phase - otherwise known as the material in the column. Separation is dependent on different mechanisms such as that of adsorption, partition, ion-exchange and size-exclusion. In this project, the two common types of HPLC encountered are normal-phase HPLC and reverse phase HPLC. The difference between these two types is that in normal-phase HPLC, the mobile phase is of a low to medium polarity while the stationary phase is of a high polarity, whereas in reverse-phase HPLC, the situation is reversed in that the the mobile phase is of a medium to high polarity while the stationary phase is of a low polarity. In turn, the result is that the least polar particles are eluted first in normal phase HPLC and the most polar particles are eluted first in reverse-phase HPLC.

The following picture gives a really rough sketch on the basic parts of a common HPLC machine:

There are variable conditions/parameters in the machine that can affect the result for a tested substance/sample. For instance, the column type, type of mobile phase, flow rate, type of detector (UV or Diode Array Detector), temperature, wavelength, elution time and injection volume. The result in turn, would be translated into a graph, whereby the peak would be directly proportional to the concentration/ quantity of a particular substance present. The concentration is determined in a way that is pretty much similar to that of a spectrophotometer, whereby a UV light would emit rays through the stream of liquid coming out of the column while a detector on the opposite side of the stream would give a direct reading of the amount of light absorbed by the liquid. This amount of light absorbed would nevertheless be directly proportional to the concentration/ amount of a particular substance flowing through the beam.

The following is an example of how a typical result might look like, whereby the X-axis represents the duration of the run, and Y-axis represents the concentration of a substance that was run at that time during one of my lab sessions in the second week.

With all of that covered, perhaps the only thing that I've left out thus far is the progress of the project to date.

As of presently, under the guidance from my patient supervisors of the project, a simple formulation for the extemporaneous product of metformin has been achieved, and the first few runs of the sample on a HPLC machine carried out. The results in turn had provided better perspective into the responsiveness of the HPLC machine being used to metformin, thus providing a stpping stone to other subsequent objectives yet to come.

Alright, that'd be all for now. Thanks for going through the thick and densely forested entry of words and hope that it'd benefitted you somewhat there. Of course, all the best to the rest of the duration of your respective attachments.

Here's signing off,

Alexander Soo, TG02.

References:

1. RxList. Glucophage Clinical Pharmacology. Retrieved 23 June, 2008 from http://www.rxlist.com/cgi/generic/metformi_cp.htm

2. WebMD. Drugs and Treatments - Metformin Oral. Retrieved 23 June, 2008 from http://www.webmd.com/drugs/mono-7061-METFORMIN+-+ORAL.aspx?drugid=11285&drugname=Metformin+Oral

3. Riomet. What is Riomet. Retrieved 23 June, 2008 from http://www.riomet.com/about.asp

4.The World Intellectual Property Organization. (2007). Effervescent Metformin Composition and Tablets and Granules Made Therefrom. Retrieved 23 June, 2008 from http://www.wipo.int/pctdb/fr/ia.jsp?ia=EP2005%2F054757&IA=EP2005%2F054757&DISPLAY=DESC

5. (2006).Metformin Hydrochloride. British Pharmacopoeia 2007 Volume II. London: The stationery Office.

6. (2000). Metformin Hydrochloride. Pharmacopoeia of the People’s Republic of China Volume II. Beijing, China: Chemical Industry Press.