Welcome all to IS PHARMACOLOGY DIFFICULT Podcast ! I am Dr Radhika Vijay, in today's episode, I will talk about a new topic from friday's pandora's Box and it has its label as Fixed Dose Drug Combinations abbreviated as FDCs. In this I will tell first and foremost the definition of FDCs, clear the fact that are not concomitant drug preparations rather formulated all in all one dosage form. Then going in a stepwise manner, I will clear three important concepts , first one that for making of an FDC, the drugs should have approximately equal half life, for making this concept crystal clear I will give you some classical wonderful examples. Second concept states that ratio of doses in these formulations depends on  apparent volume of distribution and peak plasma concentration of individual drugs should also be approximately equal, for this too, I will give you some famous classical examples that justify this conceptual statement. Thirdly, I will tell you a quick conceptual fact about cotrimoxazole where we combine individual drugs in a specific ratio to combat their gaps of values of apparent volumes of distribution so that they attain a desirable value of 1:20 concentration which gives optimal synergism. Another wonderful fact is that the theoretical and clinical ratio values do vary again , so lot of bombardment of information for the da, lets call it for a day, till next episode, do follow me here, do rate and review on ITunes, Apple podcasts, thank you!!