People take medicines in total faith on the doctor and the medical company. Patients do not have any means or knowledge to identify fake drugs.
The drugs are periodically tested by random sampling by drug control department officials through the recognised laboratories. This is a very daunting task as the number of drugs sold in the country are in many thousands, and the testing facilities are very much meagre. Moreover the results also come late which render the effort useless too as, by that time the fake medicines would have been sold out. Apart from this, the established pharmaceutical companies also do their own market intelligence and get to know what all similar medicines are marketed. They also procure such samples and test it in their laboratories and expose the fakes, more in the interest to safeguard their own business.
Reputed and established pharmaceutical companies have their own quality control labs and these are also submitted to the statutory authorities. Hence it is more or less ensured that the drugs manufactured by such companies mostly conform to the required and stipulated quality as displayed on the label of the medicine.
Fake medicines can be of two types (1). With much less potency due to the low quantum of the ingredients or due to the low quality of the ingredients. These do not cause much harm if they are not coming to be used in life saving emergency situations. The possibility is that it takes long time to get the result. (2) Totally fake without any of the supposed to be ingredients ,but have only the base holding material, and just placebos. These can be generally identified by experienced persons from the difference in taste, smell and reactive responses. If they are not used in serious illnesses, the doctor usually comes to know due to the lack of response to the medicine.
One of the general ways to identify fake medicines is that they are sold in retail and wholesale at a very low price compared to the other drugs of same content and composition.(However some generic drugs can be sold at much low prices by genuine local small scale sector manufacturers due to the relatively lesser expenses for them on advertisement, logistics etc) The second clue can be the lack of effect of the medicine after the initial doses.
Generally experienced doctors prescribe medicines of only reputed and established companies in case of serious illness even though they may be more costly. What the patient should take care is not to fall for the suggestions of alternatives by the medical shop person. if the prescribed one is not available it is better to revert back to the doctor for his suggestions for a substitute medicine.