Thiazinamium is an anti-cholinergic phenothiazine deriva¬tive, which also has antihistaminic properties. Intramuscular injection of Thiazinamium induces considerable bronchodilatation, but inconsistent results have been obtained after oral administration. The bioavailability of oral Thiazinamium is only 2-3% of that occurring after intramuscular injection. Intrarectal Thiazinamium is slightly better absorbed (3-9%). The elimination half-life of the parenteral drug is short, being about 20 minutes in most patients. Thiazinamium has been available for the treatment of asthma since the early 1960s but currently withdrawn in most countries. Compared with inhaled ipratropium bromide, intramuscular Thiazinamium and intramuscular atropine were associated with 'extremely frequent side-effects’. Notable tachycardia occurred shortly after intramuscular injection of Thiazinamium in two trials. Dry mouth was reported as ‘frequent’ with oral Thiazinamium, and micturition problems of moderate severity affected 13% of patients.

Talastine (trade name Ahanon), an alkylamine H1-antihistamine, was studied as a reason for an allergic drug exanthema.

Quifenadine is an antihistaminic agent. Quifenadine both blocks histamine H1-receptors in the peripheral tissues, and activates enzyme diaminoxidase (histaminase), due to this decreasing the histamine concentration in tissues. It is indicated in cases of pollinosis, acute and chronic urticaria, seasonal rhinitis (hay fever), allergic rhinitis, allergic conjunctivitis, angioneurotic Quinqe’s edema, dermatosis (eczema, neurodermatitis, pruritus etc.), allergic reactions caused by food or medicines. Quifanidine exhibits antiarrhythmic activity in children with frequent premature beats, without significant QT prolongation, or sinus node depression.

Tritoqualine is an inhibitor of histidine decarboxylase, an enzyme that catalyzes the conversion of histidine to histamine. Tritoqualine does not act on histamine receptors. It was marketed since 1960 for the treatment of allergic conditions and is available under tradename Hypostamine.

Rupatadine is characterised as a non-sedating H1 anti-histamine and platelet-activating factor (PAF) receptor antagonist. Rupatadine is indicated for the treatment of allergic rhinitis and urticaria. Rupatadine is a safe and well tolerated drug in patients over 2 years old, with no central nervous system or cardiovascular effects and it can be taken with or without foods.

Bilastine is a new second generation H1-antihistamine recently approved for the symptomatic treatment of allergic rhinitis (AR) and chronic urticaria (CU). Bilastine is an H1 receptor inverse agonist. Bilastine also exerts anti-inflammatory activity by inhibiting the release of histamine, IL-4 and tumor necrosis factor (TNF)-α from human mast cells and granulocytes. Common side effects are headache and drowsiness.

Oxatomide is a H1-histamine receptor antagonist developed for the treatment of broad spectrum of allergic and other hypersensitivity reactions. The drug is currently marketed in Japan, Taiwan, Italy, Portugal, Indonesia, Argentina, South Africa.

Mequitazine (PRIMALAN®) is a phenothiazine derivative and a histamine H1-receptor antagonist. It competes with histamine for the normal H1-receptor sites on effector cells of the gastrointestinal tract, blood vessels and respiratory tract. It provides effective, temporary relief of sneezing, watery and itchy eyes, and runny nose due to hay fever and other upper respiratory allergies.

Glutodine (Cyproheptadine), sold under the brand name Periactin or Peritol, is a first-generation antihistamine with additional antiserotonergic, anticholinergic and local anesthetic properties. Glutodine is a white to slightly yellowish crystalline solid, which is soluble in water, freely soluble in methanol, sparingly soluble in ethanol, soluble in chloroform, and practically insoluble in ether. Cyproheptadine is used to treat allergic reactions (specifically hay fever), Vasomotor rhinitis, Allergic conjunctivitis due to inhalant allergens and foods, uncomplicated allergic skin manifestations of urticaria and angioedema amelioration of allergic reactions to blood or plasma, Cold urticaria, and Dermatographism. Cyproheptadine is used off-label to treat Spasticity Associated With Spinal Cord, Migraine Headache Prophylaxis, Decreased Appetite Secondary to Chronic Disease, Drug-Induced Sexual Dysfunction, Serotonin Syndrome.

Carbinoxamine is a histamine-H1 receptor blocking agent. It is an antihistamine with anticholinergic (drying) and sedative properties. Carbinoxamine appears to compete with histamine (type H1) for receptor sites on effector cells in the gastrointestinal tract, blood vessels and respiratory tract. Carbinoxamine is effective for the symptomatic treatment of seasonal and perennial allergic rhinitis; vasomotor rhinitis; allergic conjunctivitis due to inhalant allergens and foods; mild, uncomplicated allergic skin manifestations of urticaria and angioedema; dermatographism; as therapy for anaphylactic reactions adjunctive to epinephrine and other standard measures after the acute manifestations have been controlled. Most common adverse reactions are: sedation, sleepiness, dizziness, disturbed coordination, epigastric distress, and thickening of bronchial secretions. Avoid concomitant use of alcohol and CNS depressants (hypnotics sedatives, tranquilizers, etc.) due to additive adverse effects.