One of the key classifications is between traditional small molecule drugs; usually derived from chemical synthesis and biological medical products; which include recombinant proteins, vaccines, blood products used therapeutically (such as IVIG), gene therapy, and cell therapy (for instance, stem cell therapies).
Pharmaceuticals or drugs or medicines are classified into various other groups besides their origin on the basis of pharmacological properties like mode of action and their pharmacological action or activity, such as by chemical properties, mode or route of administration, biological system affected, or therapeutic effects. An elaborate and widely used classification system is the Anatomical Therapeutic Chemical Classification System (ATC system). The World Health Organization keeps a list of essential medicines.
A sampling of classes of medicine includes:
# Antipyretics: reducing fever (pyrexia/pyresis)
# Analgesics: reducing pain (painkillers)
# Antimalarial drugs: treating malaria
# Antibiotics: inhibiting germ growth
# Antiseptics: prevention of germ growth near burns, cuts,and wounds
# Mood stabilizers: lithium and valproate
# Hormone replacements: Premarin
# Oral contraceptives: Enovid, "biphasic" pill, and "triphasic" pill
# Stimulants: methylphenidate, amphetamine
# Tranquilizers: meprobamate, chlorpromazine, reserpine, chlordiazepoxide, diazepam, and alprazolam
# Statins: lovastatin, pravastatin, and simvastatin
Pharmaceuticals may also be described as "specialty", independent of other classifications, which is an ill-defined class of drugs that might be difficult to administer, require special handling during administration, require patient monitoring during and immediately after administration, have particular regulatory requirements restricting their use, and are generally expensive relative to other drugs.