Hallucinogens (20) • Drugs capable of inducing illusions, hallucinations, delusions, paranoid ideations, and other alterations of mood and thinking. Despite the name, the feature that distinguishes these agents from other classes of drugs is their capacity to induce states of altered perception, thought, and feeling that are not experienced otherwise. MeSH

Hazardous Chemicals (0) see Hazardous Substances

Hazardous Substances (1) • Elements, compounds, mixtures, or solutions that are considered severely harmful to human health and the environment. They include substances that are toxic, corrosive, flammable, or explosive. MeSH

Hemagglutinins (1) • Agents that cause agglutination of red blood cells. They include antibodies, blood group antigens, lectins, autoimmune factors, bacterial, viral, or parasitic blood agglutinins, etc. MeSH

Hematinics (20) • Agents which improve the quality of the blood, increasing the hemoglobin level and the number of erythrocytes. They are used in the treatment of anemias. MeSH

Hematologic Agents (336) • Drugs that act on blood and blood-forming organs and those that affect the hemostatic system. MeSH

Hematologic Agents (1)

Hemocompatible Materials (0) see Biocompatible Materials

Hemolytic Agents (1) • Substances that are toxic to blood in general, including the clotting mechanism; hematotoxins may refer to the hematopoietic system. MeSH

Hemostatics (43) • Agents acting to arrest the flow of blood. Absorbable hemostatics arrest bleeding either by the formation of an artificial clot or by providing a mechanical matrix that facilitates clotting when applied directly to the bleeding surface. These agents function more at the capillary level and are not effective at stemming arterial or venous bleeding under any significant intravascular pressure. MeSH

Hemotoxins (0) see Hemolytic Agents

Heparin Antagonists (5) • Coagulant substances inhibiting the anticoagulant action of heparin. MeSH

Herbicides (100) • Pesticides used to destroy unwanted vegetation, especially various types of weeds, grasses (POACEAE), and woody plants. Some plants develop HERBICIDE RESISTANCE. MeSH

High Ceiling Diuretics (0) see Sodium Potassium Chloride Symporter Inhibitors

Histamine (1)

Histamine Agents (135) • Drugs used for their actions on histaminergic systems. Included are drugs that act at histamine receptors, affect the life cycle of histamine, or affect the state of histaminergic cells. MeSH

Histamine Agonists (10) • Drugs that bind to and activate histamine receptors. Although they have been suggested for a variety of clinical applications histamine agonists have so far been more widely used in research than therapeutically. MeSH

Histamine Antagonists (123) • Drugs that bind to but do not activate histamine receptors, thereby blocking the actions of histamine or histamine agonists. Classical antihistaminics block the histamine H1 receptors only. MeSH

Histamine Effect (0) see Histamine Agents

Histamine H1 Agonists (0) see Histamine Agonists

Histamine H1 Antagonists (73) • Drugs that selectively bind to but do not activate histamine H1 receptors, thereby blocking the actions of endogenous histamine. Included here are the classical antihistaminics that antagonize or prevent the action of histamine mainly in immediate hypersensitivity. They act in the bronchi, capillaries, and some other smooth muscles, and are used to prevent or allay motion sickness, seasonal rhinitis, and allergic dermatitis and to induce somnolence. The effects of blocking central nervous system H1 receptors are not as well understood. MeSH

Histamine H1 Antagonists, Non-Sedating (17) • A class of non-sedating drugs that bind to but do not activate histamine receptors (DRUG INVERSE AGONISM), thereby blocking the actions of histamine or histamine agonists. These antihistamines represent a heterogenous group of compounds with differing chemical structures, adverse effects, distribution, and metabolism. Compared to the early (first generation) antihistamines, these non-sedating antihistamines have greater receptor specificity, lower penetration of BLOOD-BRAIN BARRIER, and are less likely to cause drowsiness or psychomotor impairment. MeSH

Histamine H2 Agonists (0) see Histamine Agonists

Histamine H2 Antagonists (19) • Drugs that selectively bind to but do not activate histamine H2 receptors, thereby blocking the actions of histamine. Their clinically most important action is the inhibition of acid secretion in the treatment of gastrointestinal ulcers. Smooth muscle may also be affected. Some drugs in this class have strong effects in the central nervous system, but these actions are not well understood. MeSH

Histamine H3 Agonists (0) see Histamine Agonists

Histamine H3 Antagonists (5) • Drugs that selectively bind to but do not activate HISTAMINE H3 RECEPTORS. They have been used to correct SLEEP WAKE DISORDERS and MEMORY DISORDERS. MeSH

Histone Deacetylase Inhibitors (26) • Compounds that inhibit HISTONE DEACETYLASES. This class of drugs may influence gene expression by increasing the level of acetylated HISTONES in specific CHROMATIN domains. MeSH

HIV Fusion Inhibitors (6)

HIV Integrase Inhibitors (7) • Inhibitors of HIV INTEGRASE, an enzyme required for integration of viral DNA into cellular DNA. MeSH

HIV Protease Inhibitors (16) • Inhibitors of HIV PROTEASE, an enzyme required for production of proteins needed for viral assembly. MeSH

Hormone Antagonists (181) • Chemical substances which inhibit the function of the endocrine glands, the biosynthesis of their secreted hormones, or the action of hormones upon their specific sites. MeSH

Hormone Receptor Agonists (0) see Hormones

Hormones (202) • Chemical substances having a specific regulatory effect on the activity of a certain organ or organs. The term was originally applied to substances secreted by various ENDOCRINE GLANDS and transported in the bloodstream to the target organs. It is sometimes extended to include those substances that are not produced by the endocrine glands but that have similar effects. MeSH

Hormones, Hormone Substitutes, and Hormone Antagonists (218)

Humectants (0) see Hygroscopic Agents

Hydrocholeretics (0) see Cholagogues and Choleretics

Hydroxymethylglutaryl-CoA Reductase Inhibitors (25) • Compounds that inhibit HMG-CoA reductases. They have been shown to directly lower cholesterol synthesis. MeSH

Hygroscopic Agents (2) • Materials that readily absorb moisture from their surroundings. MeSH

Hypnotic Effect (0) see Hypnotics and Sedatives

Hypnotics (0) see Hypnotics and Sedatives

Hypnotics and Sedatives (78) • Drugs used to induce drowsiness or sleep or to reduce psychological excitement or anxiety. MeSH

Hypocholesteremic Agents (0) see Anticholesteremic Agents

Hypoglycemic Agents (121) • Substances which lower blood glucose levels. MeSH

Hypoglycemic Effect (0) see Hypoglycemic Agents

Hypolipidemic Agents (116) • Substances that lower the levels of certain LIPIDS in the BLOOD. They are used to treat HYPERLIPIDEMIAS. MeSH