 "Would you like me to fill that prescription with the generic equivalent?" "No thank you, I'll take the real thing." This unfortunate exchange occurs all too frequently in retail pharmacies bringing to mind the question, what is the "real thing"? Is opting for a generic equivalent to your prescription medication the same as opting for a generic detergent or generic paper plates? The answer, in a word, is NO.
To be marketed in the United States, all prescription drugs must be approved by the Food and Drug Administration (FDA) as safe and effective. This means a drug company or whoever discovers the new drug entity, must first file a new drug application (NDA) with the FDA. Once the NDA is accepted, the drug company may begin trials on animals and finally humans to prove the safety and effectiveness of the drug. Upon proving the safety and efficacy of the drug, the discovering company is granted permission by the FDA to market the drug under the brand (proprietary) name. In addition to granting permission to market the new drug, the FDA also grants a period of exclusivity to the discovering manufacturer. This means that for a specified number of years (usually between 4 and 7) no other company is allowed to manufacture the new drug. There are several reasons for exclusivity, the most significant of which is to maintain the incentive for pioneering companies to continue researching and discovering new drug entities.
During the period of exclusivity, other drug companies are itching to reproduce the newly approved drug because the legwork has already been done. The manufacturer that submits the NDA has already spent enormous amounts of money in research to bring the product to market. The company marketing the generic product, on the other hand, is only required to submit an abbreviated new drug application (ANDA), which does not require them to reprove what the pioneer manufacturer has already proven i.e., the efficacy of the drug entity. The generic company therefore saves millions of dollars in research and development as they are simply duplicating what has already been done. This savings allows the generic drug manufacturer to market the drug at a much lower price than that charged by the original manufacturer.
 Having said that, not all drugs approved as generics are equivalent to the original drug entity. For this reason the FDA has established a rating system to determine the equivalence of generic drugs to the standard (original drug entity). Without going into great detail, I will suffice it to say that drugs rated AB are determined to be equivalent in all ways to the original drug. This means that taking one tablet of the generic drug will produce the same blood concentration, elimination rate and efficacy as the original drug +/- 5% (which is an insignificant difference for a majority of drugs).
For a minority of drug products termed "narrow therapeutic index" drugs (including but not limited to levothyroxine, phenytoin, warfarin, theophylline, lithium, digoxin, etc.) an AB rating means the generic product is as safe and effective as the brand, however these drugs require close monitoring by the physician. In other words patients on these drugs (brand or generic) must have blood levels drawn at various intervals to assure the blood concentration of these medications is not a toxic one, as narrow therapeutic index means that the window between an effective dose and a toxic dose of these medications is very small. In other words, when switching from brand to generic or vice versa one must have their dose reassessed by the physician. You might ask, "If these drugs are equivalent, why is it necessary to reassess the dose when switching between them?" This is because all individuals absorb, metabolize and eliminate drugs at a slightly different rate based on their unique physiology, so although the drugs are just as safe and effective, the slightest variation in absorption, metabolism or elimination may have a larger impact on blood concentration of narrow therapeutic index drugs.
 The bottom line is that an AB rated generic drug has been proven by the FDA to be equivalent to the original brand name product and with the exception of the narrow therapeutic index drugs can be interchanged with the same expectations as the more expensive brand name product. In the face of ever increasing health care costs, one cannot afford to opt for a more expensive brand of the same AB rated medication when there is no therapeutic benefit to be expected from that product. Insurance companies have also begun to recognize generics as a prime candidate for cutting healthcare costs by shifting some of the burden to the consumer who chooses brand when an equivalent generic is available. 
(This article was contributed by Feisal Rauhi Othman, Pharm.D., R.Ph.) |
