For pharmaceutical companies, it takes billions of dollars to develop a new medication, along with years of research and revisions to achieve regulatory approval. Drug manufacturers want to maintain the profits and rights to their flagship medications, attempting to protect profits, patent products and block less expensive generic versions.

That’s one of the reasons Americans pay the most for prescription drugs in the world.

Congress passed a law requiring drug companies to provide samples of their products, which would allow for the development of generic equivalents. This intention is to increase competition and ultimately lower drug prices.

Samples are required for bioequivalence testing, which is necessary for a generic drug to be approved. By refusing to provide samples, the companies are delaying the formulation and availability of cheaper options.

Which companies are blocking generic drugs?

The U.S. Food and Drug Administration (FDA) has publicly released a list of companies that may be intentionally delaying generic drugs. As part of the FDA’s Drug Competition Action Plan (DCAP) to support government efforts for affordable medications, the agency is focusing on transparency.

The FDA has received more than 150 inquiries from generic drug makers looking to access samples from manufacturers. Some companies that have yet to comply include GlaxoSmithKline, Pfizer, Valeant Pharmaceuticals International, BioMarin Pharmaceutical, Gilead Sciences and Novartis Pharmaceuticals.

What drugs are being blocked from generic development?

Many of the drugs manufactured by these companies are necessary or life-saving medications. One medication, Revlimid (lenalidomide), which treats multiple myeloma and other related diseases, currently costs $20,000 a month. Tracleer (bosentan), which is used to treat pulmonary arterial hypertension, costs $12,000 a month, according to GoodRx.

Other drugs include Truvada, the blockbuster medication used to prevent HIV infection, and Clozaril, which is used to treat schizophrenia and suicidal thinking. Also listed is Accutane, a treatment for severe cystic acne.

To urge compliance from manufacturers, the FDA has listed the companies who have yet to provide samples for generics:

For more information, please review the Reference Listed Drug (RLD) Access Inquiries or visit FDA.gov.

Drug Name

Drug Manufacturer

Absorica (isotretinoin)

RANBAXY INC/SUN PHARMACEUTICAL INDUSTRIES INC

Abstral (fentanyl citrate)

GALENA BIOPHARMA

Accutane (isotretinoin)

ROCHE PALO ALTO LLC

Adempas (riociguat)

BAYER HEALTHCARE PHARMACEUTICALS INC

Afinitor (everolimus)

NOVARTIS PHARMACEUTICALS CORP

Amnesteem (isotretinoin)

MYLAN PHARMACEUTICALS INC

Ampyra (dalfampridine)

ACORDA THERAPEUTICS INC

Brilinta (ticagrelor)

ASTRAZENECA LP

Claravis (isotretinoin)

TEVA PHARMACEUTICALS USA

Clozaril (clozapine)

HERITAGE LIFE SCIENCES BARBADOS INC

Cystadane (betaine hydrochloride)

ORPHAN EUROPE SARL

Embeda (morphine sulfate; naltrexone hydrochloride)

ALPHARMA PHARMACEUTICALS LLC KING PHARMACEUTICALS

Entereg (alvimopan)

CUBIST PHARMACEUTICALS INC

Exjade (deferasirox)

NOVARTIS PHARMACEUTICALS CORP

Fazaclo ODT (clozapine)

JAZZ PHARMACEUTICALS III INTERNATIONAL LTD

Fentora (fentanyl citrate)

CEPHALON INC

Ferriprox (deferiprone)

APOPHARMA INC

Firazyr (icatibant acetate)

SHIRE ORPHAN THERAPIES INC

Gattex Kit (teduglutide recombinant)

NPS PHARMACEUTICALS INC

Gilotrif (afatinib dimaleate)

BOEHRINGER INGELHEIM

H.P. Acthar Gel (corticotropin)

QUESTCOR PHARMACEUTICALS INC

Hemabate (carboprost tromethamine)

PHARMACIA AND UPJOHN CO

Juxtapid (lomitapide mesylate)

AEGERION PHARMACEUTICALS INC

Korlym (mifepristone)

CORCEPT THERAPEUTICS INC

Kuvan (sapropterin dihydrochloride)

BIOMARIN PHARMACEUTICAL INC

Letairis (ambrisentan)

GILEAD SCIENCES INC

Methadone Hydrochloride (methadone hydrochloride)

ROXANE LABORATORIES INC

Mifeprex (mifepristone)

DANCO LABORATORIES LLC

Nexavar (sorafenib tosylate)

BAYER HEALTHCARE PHARMACEUTICALS INC

Onsolis (fentanyl citrate)

MEDA PHARMACEUTICALS INC

Opsumit (macitentan)

ACTELION PHARMACEUTICALS LTD

Orfadin (nitisinone)

SWEDISH ORPHAN BIOVITRUM AB PUBL

Pomalyst (pomalidomide)

CELGENE CORP

Promacta (eltrombopag olamine)

GLAXOSMITHKLINE

Qsymia (phentermine hydrochloride; topiramate)

VIVUS INC

Ravicti (glycerol phenylbutyrate)

HYPERION THERAPEUTICS INC

Revlimid (lenalidomide)

CELGENE CORP

Sabril (vigabatrin) for solution

LUNDBECK LLC / LUNDBECK PHARMACEUTICALS LLC

Sabril (vigabatrin) tablet

LUNDBECK LLC / LUNDBECK PHARMACEUTICALS LLC

Subsys (fentanyl)

INSYS THERAPEUTICS INC

Tasigna (nilotinib hydrochloride monohydrate)

NOVARTIS PHARMACEUTICALS CORP

Tecfidera (dimethyl fumarate)

BIOGEN IDEC INC

Thalomid (thalidomide)

CELGENE CORP

Tikosyn (dofetilide)

PFIZER PHARMACEUTICALS PRODUCTION CORP LTD

Tracleer (bosentan)

ACTELION PHARMACEUTICALS LTD

Truvada (emtricitabine; tenofovir disoproxil fumarate)

GILEAD SCIENCES INC

Tykerb (lapatinib ditosylate)

SMITHKLINE BEECHAM CORP DBA GLAXOSMITHKLINE

Veletri (epoprostenol sodium)

ACTELION PHARMACEUTICALS LTD

Xenazine (tetrabenazine)

VALEANT INTERNATIONAL BERMUDA/VALEANT PHARMACEUTICALS NORTH AMERICA LLC

Zavesca (miglustat)

ACTELION PHARMACEUTICALS LTD

Zortress (everolimus)

NOVARTIS PHARMACEUTICALS CORP