You can structure your blog entry however you see fit, however you should include the following information:
Introduction:
You should briefly describe the purpose and aims of the study you are describing. Remember your audience is GPs and pharmacists. You shouldn't need to give long explanations of common medical conditions. Remember that the marks are awarded for your description and critical analysis of the research.
Description of methods:
Think carefully about including the most important details in the methods, because you will not be able to include all the details. You should include details of the the experimental protocol, but do not forgot to mention what was measured (and how) and what the primary end point of the study was (or which value was compared between groups.). As your critical analysis is largely dependent on the methods, it is important to make clear how the experiment was conducted.
Description of results:
It is important to discuss the most important results quantitatively and to consider the most important information to include in a short summary. Don't be tempted to write too much about statistical significance, without commenting on the size of the effect measured. Many papers will include lots of measurements, you need to consider which are the most important, as you won't have room to discuss them all.
Critical analysis:
This is probably the most difficult section (and consequently, where the most marks are available). Essentially, you should aim to consider the work critically, rather than simply accepting the authors' conclusion. You can approach this task by asking questions such as: Were the methods (and endpoints) appropriate? What do the results mean? Is the authors' interpretation of the results supported by the data?
You should try to judge each paper on its own merits. If a paper set out to test the hypothesis that ‘dogs enjoy eating bones' it's not really fair to criticise it for not asking whether cats like eating bones. Proposing an extension to a study (however interesting) is not critical analysis. You may wish, briefly, to discuss the implications of the research which is again interesting but is not critical analysis.
Try to keep your critical analysis specific rather than general for example, rather than automatically saying ‘the experiment would have been better if the sample size had been bigger' consider whether this is really the case. In very may experiments it is true, but it requires some justification. Experimenters don't usually pick a sample size (n number) out of thin air, they will perform calculations to work out the sample size they need. A trial that is bigger than it needs to be costs more money and may have ethical implications relating to unnecessary experimentation on volunteers or animals. A comment along the lines of ‘the authors don't state how they calculated their sample size' or ‘the authors calculated their sample size but were not able to recruit enough volunteers' is a much more useful indication that something is wrong.