Generic substitutes for brand-name medications must first win the approval of the FDA before they can be marketed. Generic drugmakers submit an abbreviated new drug application, or ANDA, that is similar in most respects to the New Drug Applications, or NDAs, submitted for new and previously unmarketed prescription drugs.
NDAs must be accompanied by data from clinical trials designed to show that the proposed new drug achieves its medical goals with minimal adverse side effects. ANDAs do not require all this clinical trial data, because the drug’s efficacy and safety have already been established by the manufacturer of the brand-name drug.
However, the FDA has certain criteria that must be met by any would-be generic drug manufacturer. The proposed generic must contain the same active ingredient at the same strength(s) as the brand-name drug. It must also use the same dosage form — tablet, capsule, or liquid — and the same route of administration, whether oral or injectable.
However, generic drugs need not contain the same inactive ingredients as the brand-name drug for which they are offered as substitutes, but the FDA reserves the right to deny an ANDA if it disapproves of the inactive ingredients used in a generic. Inactive ingredients typically serve as filler material and coloring agents.
Because they are inactive, these substances are inert chemically and unlikely to cause any ill effects in those taking the drugs. Thus, all generic Viagra must have sildenafil citrate as an active ingredient and must be offered in the same dosage strengths as the brand-name drug — 25-, 50-, and 100-milligram tablets.
Because the generics’ inactive ingredients can be different from those in the branded drug, generics might look nothing at all like the latter, apart from being available in tablet form.