All drugs are required to get a clearance from the FDA. Depending on characteristics of the drugs, different clearance paths are available, and respective cost and approval period would vary as well.

New Drug Application (NDA)
Abbreviated New Drug Application (ANDA)
Over-the-counter (OTC) Drug Monographs
Pre-clinical Trials
Investigational New Drug (IND)
Clinical Trials

New Drug Application (NDA)
Every new drug is required to have approval of its NDA before U.S. commercialization.

NDA Classifications
Center for Drug Evaluation and Research (CDER) classifies new drug applications with a code that reflects both the type of drug being submitted and its intended uses. The numbers 1 through 7 are used to describe the type of drug:

New Molecular Entity
New Salt of Previously Approved Drug (not a new molecular entity)
New Formulation of Previously Approved Drug (not a new salt OR a new molecular entity)
New Combination of Two or More Drugs
Already Marketed Drug Product - Duplication (i.e., new manufacturer)
New Indication (claim) for Already Marketed Drug (includes switch in marketing status from prescription to OTC)
Already Marketed Drug Product - No Previously Approved NDA

The following letter codes describe the review priority of the drug:

S - Standard review for drugs similar to currently available drugs.
P - Priority review for drugs that represent significant advances over existing treatments.

Fundamentals of NDA Submissions
Although the quantity of information and data submitted in NDA,s can vary significantly, the components of NDA,s are more uniform. NDA,s can consist of as many as 15 different sections:

Index
Summary
Chemistry, Manufacturing, and Control
Samples, Methods Validation Package, and Labeling
Non-clinical Pharmacology and Toxicology
Human Pharmacokinetics and Bioavailability
Microbiology (for anti-microbial drugs only)
Clinical Data
Safety Update Report (typically submitted 120 days after the NDA's submission)
Statistical Information
Case Report Tabulations
Case Report Forms
Patent Information
Patent Certification
Other Information

Abbreviated New Drug Application (ANDA)

An ANDA, like NDA,s, contains data for the review and ultimate approval of a generic drug product. A generic drug product is one that is comparable to an innovator drug product in dosage form, strength, route of administration, quality, performance characteristics and intended use.

Generic drug applications are termed "abbreviated" because they are generally not required to include pre-clinical (animal) and clinical (human) data to establish safety and effectiveness. Instead, generic applicants must scientifically demonstrate that their product is bioequivalent (i.e., performs in the same manner as the innovator drug).

The generic version must deliver the same amount of active ingredients into a patient's bloodstream in the same amount of time as the innovator drug.

Over-the-counter (OTC) Drug Monograph

OTC drug products are those drugs that are available to consumers without a prescription. There are more than 80 classes (therapeutic categories) of OTC drugs, ranging from acne drug products to weight control drug products. There are more than 100,000 OTC drug products marketed, encompassing about 800 significant active ingredients.

OTC drug monographs specify acceptable ingredients, doses, formulations, labeling, and testing for each class of products. OTC drug monographs are continually updated to add additional ingredients and labeling as needed. Products that are not conforming to a monograph must undergo separate review and approval through the New Drug Application (NDA) process.

The NDA process, and not the monograph process, is also used for new ingredients entering the OTC marketplace for the first time. For example, the newer OTC drug products (previously available only by prescription) are first approved through the NDA process and their "switch" to OTC status is approved via the NDA process.

Pre-clinical Trials

Under the FDA requirements, a sponsor must first submit data showing that the drug is reasonably safe for use in initial, small-scale clinical studies. The sponsor may have several options for fulfilling this requirement:

(1) Using existing non-clinical data from past in vitro laboratory or animal studies on the compound;
(2) Compiling data from previous clinical testing or marketing of the drug in the United States or another country whose population is relevant to the U.S. population; or
(3) Undertaking new pre-clinical studies designed to provide the evidence necessary to support the safety of administering the compound to humans.

Investigational New Drug (IND)

In many ways, the investigational new drug (IND) application is the result of a successful pre-clinical development program. The IND is also the vehicle through which a sponsor advances to the next stage of drug development known as clinical trials (human trials). However, the IND is not an application for marketing approval.

Generally, this includes data and information in three broad areas:
Animal Pharmacology and Toxicology Studies
Manufacturing (Product) Information
Clinical Protocols and Investigator Information

Clinical Trials (Human)

The new drug application (NDA) is the vehicle through which drug sponsors formally propose that the FDA approve a new pharmaceutical for sale in the United States. To obtain this authorization, a drug manufacturer submits in an NDA non-clinical (animal) and clinical (human) test data and analyses, drug information, and descriptions of manufacturing procedures.

An NDA must provide sufficient information, data, and analyses to permit the FDA reviewers to reach several key decisions, including:

Whether the drug is safe and effective for its proposed use(s), and whether the benefits of the drug outweigh its risks.
Whether the drug,s proposed labeling is appropriate, and, if not, what the drug's labeling should contain.
Whether the methods used in manufacturing the drug and the controls used to maintain the drug's quality are adequate to preserve the drug's identity, strength, quality, and purity.