H1 antagonists, also called H1 blockers, are a class of medications that block the action of histamine at the H1 receptor, helping to relieve allergic reactions. Agents where the main therapeutic effect is mediated by negative modulation of histamine receptors are termed antihistamines; other agents may have antihistaminergic action but are not true antihistamines.
Diphenhydramine (DPH) is an antihistamine and sedative mainly used to treat allergies, insomnia, and symptoms of the common cold. It is also less commonly used for tremors in parkinsonism, and nausea. It is taken by mouth, injected into a vein, injected into a muscle, or applied to the skin. Maximal effect is typically around two hours after a dose, and effects can last for up to seven hours.
Chlorphenamine, also known as chlorpheniramine, is an antihistamine used to treat the symptoms of allergic conditions such as allergic rhinitis. It is taken orally. The medication takes effect within two hours and lasts for about 4-6 hours.
Promethazine, sold under the brand name Phenergan among others, is a first-generation antihistamine, antipsychotic, sedative, and antiemetic used to treat allergies, insomnia, and nausea. It may also help with some symptoms associated with the common cold and may also be used for sedating people who are agitated or anxious, an effect that has led to some recreational use. Promethazine is taken by mouth (oral), as a rectal suppository, or by injection into a muscle (IM).
Dihydrocodeine is a semi-synthetic opioid analgesic prescribed for pain or severe dyspnea, or as an antitussive, either alone or compounded with paracetamol (acetaminophen) or aspirin. It was developed in Germany in 1908 and first marketed in 1911.
Doxylamine, sold under the brand name Unisom among others, is an antihistamine medication which is used in the treatment of insomnia and allergies. It is also used to treat morning sickness in pregnant women in combination with pyridoxine (vitamin B6). Doxylamine is available over-the-counter, and is used in nighttime cold medicines, such as NyQuil, as well as in pain medications containing acetaminophen and codeine, to help with sleep. The medication is taken by mouth.
Clemastine, also known as meclastin, is a first-generation H1 histamine antagonist (antihistamine) with anticholinergic properties (drying) and sedative side effects. Like all first-generation antihistamines, it is sedating.
Doxepin is a medication belonging to the tricyclic antidepressant (TCA) class of drugs used to treat major depressive disorder, anxiety disorders, chronic hives, and insomnia. For hives it is a less preferred alternative to antihistamines. It has a mild to moderate benefit for sleeping problems. It is used as a cream for itchiness due to atopic dermatitis or lichen simplex chronicus.
Dimetapp is an American brand of over-the-counter cold and allergy medicines that is manufactured by Foundation Consumer Brands. At one point, Dimetapp as a household word referred to a single combination preparation marketed to relieve symptoms of the common cold, containing brompheniramine and phenylephrine. Variants were created, including Dimetapp DM with the addition of dextromethorphan. Dimetapp Elixir and Colour Free Elixir are intended to relieve nasal congestion, runny nose, itchy watery eyes and sneezing, whereas Dimetapp DM and Dimetapp DM Colour Free Elixir are intended for colds with dry coughs and also to treat whooping cough. Early Dimetapp was flavored with cherry and plum as they were readily available during the time, setting a precedent for its purple color; however, the flavor has been described as a grape candy.
Orphenadrine is an anticholinergic drug of the ethanolamine antihistamine class; it is closely related to diphenhydramine. It is a muscle relaxant that is used to treat muscle pain and to help with motor control in Parkinson's disease, but has largely been superseded by newer drugs. It is considered a dirty drug due to its multiple mechanisms of action in different pathways. It was discovered and developed in the 1940s.
Zimelidine was one of the first selective serotonin reuptake inhibitor (SSRI) antidepressants to be marketed. It is a pyridylallylamine, and is structurally different from other antidepressants.
Trimipramine, sold under the brand name Surmontil among others, is a tricyclic antidepressant (TCA) which is used to treat depression. It has also been used for its sedative, anxiolytic, and weak antipsychotic effects in the treatment of insomnia, anxiety disorders, and psychosis, respectively. The drug is described as an atypical or "second-generation" TCA because, unlike other TCAs, it seems to be a fairly weak monoamine reuptake inhibitor. Similarly to other TCAs however, trimipramine does have antihistamine, antiserotonergic, antiadrenergic, antidopaminergic, and anticholinergic activities.
Chloropyramine is a classical first-generation antihistamine drug approved in Eastern European countries for the treatment of allergic conjunctivitis, allergic rhinitis, bronchial asthma, and other atopic (allergic) conditions. Related indications for clinical use include angioedema, allergic reactions to insect bites, food and drug allergies, and anaphylactic shock.
Dexbrompheniramine is an antihistamine with anticholinergic properties used to treat allergic conditions such as hay fever or urticaria. It is the pharmacologically active dextrorotatory isomer of brompheniramine. It was formerly marketed in combination with pseudoephedrine under the name Drixoral in the US and Canada. It is an alkylamine antihistamine.
Pheniramine is an antihistamine with anticholinergic properties used to treat allergic conditions such as hay fever or urticaria. It has relatively strong sedative effects, and may sometimes be used off-label as an over-the-counter sleeping pill in a similar manner to other sedating antihistamines such as diphenhydramine. Pheniramine is also commonly found in eyedrops used for the treatment of allergic conjunctivitis.
Tripelennamine, sold under the brand name Pyribenzamine by Novartis, is a drug that is used as an antipruritic and first-generation antihistamine. It can be used in the treatment of asthma, hay fever, rhinitis, and urticaria, but is now less common as it has been replaced by newer antihistamines. The drug was patented at CIBA, which merged with Geigy into Ciba-Geigy, and eventually becoming Novartis.
Dimetindene, also sold under the brand name Fenistil, is an antihistamine/anticholinergic. It is a first generation selective H1 antagonist. Dimetindene is an atypical first generation H1 antagonist as it only minimally passes across the blood–brain barrier.
Antihistamines are drugs which treat allergic rhinitis, common cold, influenza, and other allergies. Typically, people take antihistamines as an inexpensive, generic drug that can be bought without a prescription and provides relief from nasal congestion, sneezing, or hives caused by pollen, dust mites, or animal allergy with few side effects. Antihistamines are usually for short-term treatment. Chronic allergies increase the risk of health problems which antihistamines might not treat, including asthma, sinusitis, and lower respiratory tract infection. Consultation of a medical professional is recommended for those who intend to take antihistamines for longer-term use.
Bromazine, sold under the brand names Ambodryl, Ambrodil, and Deserol among others, also known as bromodiphenhydramine, is an antihistamine and anticholinergic medication of the ethanolamine class. It is an analogue of diphenhydramine with a bromine substitution on one of the phenyl rings.
PPPA, or 3-phenoxy-3-phenylpropan-1-amine, is a drug which is described as an antidepressant. It was derived by Eli Lilly from the antihistamine diphenhydramine, a diphenylmethane derivative with additional properties as a selective serotonin reuptake inhibitor (SSRI), and has been the basis for the subsequent discovery of a number of other antidepressant drugs.
