Medicines & Therapeutics

Background Information

Medicines and therapeutics are substances used in the treatment of illnesses or symptoms. They are available to individuals through physician prescriptions and over the counter.

Medicines and therapeutics may be found in many forms, such as tablets, capsules, softgels, gelcaps, liquids, or powders. Botanical dietary supplements are not included with medicines and therapeutics.

NTP has received a number of requests to study medicines and therapeutics from the public and several federal agencies. People are concerned about their safety. Manufacturers who want to distribute a medicine or therapeutic must receive approval from the U.S. Food and Drug Administration before putting it on the market. However, not all effects may be apparent during clinical testing. There may be:

  • Additional indications for the medicine
  • Off-label uses
  • Side effects that may be deemed a necessary risk because the overall effect significantly improves an illness or disease
  • Side effects that are only noted in a certain subpopulation

For these reasons, NTP is studying select medicines and therapeutics to identify potential harm from short-term and long-term exposure.

NTP Studies & Findings

NTP is conducting numerous studies in rodents to identify potential harm from short-term and long-term exposure to select medicines and therapeutics. These studies will provide toxicology data that can be used by the U.S. Food and Drug Administration, National Institutes of Health, public, and other stakeholders. The data will help in evaluating the safety of certain medicines and therapeutics.

The following tables list ongoing and completed NTP studies on medicines and therapeutics. The Testing Status column includes links to the testing status page and any available reports or updates.

Ongoing NTP Studies
Medicine/Therapeutic Commonly Used For Testing Status
Azidothymidine (AZT) drug combinations, transplacental/carcinogenesis study Treatment of HIV-AIDS Ongoing
Azidothymidine (AZT) drug combinations, transplacental/neonatal study Treatment of HIV-AIDS Ongoing
2',3'-Dideoxycytidine Treatment of HIV-AIDS Ongoing
Efavirenz (EFV) Treatment of HIV-AIDS Ongoing
Efavirenz (EFV), Emtricitabine (FTC), Tenofovir Disoproxil Fumarate (TDF) combination Treatment of HIV-AIDS Ongoing
Emtricitabine (FTC) Treatment of HIV-AIDS Ongoing
Ethinyl estradiol Treatment of breast and prostate cancer Ongoing
Fenofibrate Reduce cholesterol and triglycerides Ongoing
Hydroxyurea Chemotherapeutic agent Ongoing
Phenobarbital Anticonvulsant, hypnotic, sedative Ongoing
Simvastatin Cholesterol-lowering medication that blocks the production of cholesterol Ongoing
Tenofovir Treatment of HIV-AIDS Ongoing
Tenofovir Disoproxil Fumarte (TDF) Treatment of HIV-AIDS Ongoing
Completed NTP Studies
Medicine/Therapeutic Commonly Used For Testing Status
Acetaminophen Pain relief Completed
3’-Azido-3’-deoxythymidine (AZT) Treatment of HIV-AIDS Completed
3’-Azido-3’-deoxythymidine (AZT), transplacental carcinogenesis study Treatment of HIV-AIDS Completed
3’-Azido-3’-deoxythymidine and Isoiazid Combinations (AZT) Treatment of HIV-AIDS Completed
3’-Azido-3’-deoxythymidine (AZT), Lamivudine (3TC), Nevirapine (NVPT) Treatment of HIV-AIDS Completed
3’-Azido-3’-deoxythymidine (AZT) + Pyrazinamide combination Treatment of HIV-AIDS Completed
3’-Azido-3’-deoxythymidine (AZT) + Rifabutin Treatment of HIV-AIDS Completed
3’-Azido-3’-deoxythymidine (AZT) + Rifampin Treatment of HIV-AIDS Completed
3’-Azido-3’-deoxythymidine (AZT) + Trimethoprim/Sulfamethoxazole Treatment of HIV-AIDS Completed
Barium chloride dihydrate Cardiac stimulant Completed
Chloral hydrate Sedative Completed
Codeine Pain relief and sedatives Completed
5,5-Diphenylhydantoin Antiepileptic and antiarrhythmic drug Completed
Elmiron Prevention of thrombosis and hyperlipidemia in foreign countries and for the treatment of interstitial cystitis in the U.S. Completed
Emodin Laxative Completed
Interferon Treatment of HIV-AIDS Completed
Methylene blue trihydrate Antihemoglobinemic, cyanine poisoning antidote Completed
Methylphenidate hydrochloride Treatment of narcolepsy Completed
Oxazepam Sedative-hypnotic and antianxiety agent Completed
Oxymetholone Promote weight gain Completed
Phenolphthalein Laxative Completed
Primidone Management of partial grand mal and psychomotor seizures Completed
Promethazine hydrochloride Antihistamine Completed
Pyrazinamide Treatment of HIV-AIDS Completed
Salicylazosulfapyridine Treatment of ulcerative colitis and Crohn's disease Completed
Scopolamine hydrobromide trihydrate Sedative and treatment of motion sickness Completed
1-trans-delta-9-Tetrahydrocannabinol Topical use in hypertensive glaucomas Completed
Triamterene Diuretic Completed

Informational Resources

Resources From Other Organizations

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  • Additional Research

    Human Immunodeficiency Virus (HIV) Therapeutics


    An estimated 35 million people worldwide are living with HIV. That number includes about one million pregnant women who need treatment to prevent mother-to-child transmission of the virus during pregnancy, labor, and delivery. Azidothymidine (AZT), the first FDA-approved anti-HIV agent, is often combined with other HIV drugs that target different aspects of viral replication. Because HIV drugs are administered in combination, NTP is studying commonly used combinations (AZT, nevirapine, nelfinavir, and/or lamivudine) to characterize any potential toxicity to the offspring.

    The World Health Organization has recommended the triple combination of tenofovir (TDF), emtricitabine (FTC), and efavirenz (EFV) as standard therapy for all HIV-positive individuals. While there is great benefit from this therapy, potential toxicity for the offspring is not known.

    NTP is conducting studies to determine the potential effect of the TDF, FTC, and EFV triple combination therapy on fetal and postnatal development. The results of these studies will inform regulatory agencies worldwide of the impact on these drugs during pregnancy.



    Hydroxyurea is a pharmaceutical which was originally approved for use in cancer chemotherapy. It is also currently used for treatment of sickle cell anemia and other rare, serious diseases.

    Though hydroxyurea is not labeled for use in children with sickle cell anemia, clinical trials in infants and children have shown efficacy in preventing vaso-occlusive crises, a common complication of sickle cell anemia. Furthermore, off-label use in infants, children, and pregnant women with sickle cell anemia is increasing.

    Published reports indicate that use of hydroxyurea can cause DNA damage and induce certain cancers. Limited human and animal data also indicate adverse effects on reproduction in males. Hydroxyurea has also been shown to cause birth defects.

    In 2008, NTP published an NTP-CERHR Monograph on hydroxyurea which evaluated effects on reproduction and development. New studies have noted the importance of reviewing chronic use. NTP is conducting studies to determine the potential effect of chronic hydroxyurea exposure during periods of critical development ranging from gestational exposure through adolescence. The results of these studies can inform regulatory agencies and contribute to risk-benefit decision making and patient counseling.