Methaphenilene, an antihistaminic agent, was studied as a peroxisome proliferator. Information about the current use of this compound is not available.

Emedastine is an antihistaminic agent, which was approved by FDA for the treatment of allergic conjunctivitis (Emadine brand name). The drug acts selectively on H1 receptors with lower affinity to H2 and H3 subtypes. Emedastine has a relatively unfavorable CNS effect profile. A small percentage of patients reported somnolence as an adverse effect after administration.

Levocabastine (trade name Livo) is a selective second-generation H1-receptor antagonist used for allergic conjunctivitis. Levocabastine binds the G protein-coupled neurotensin receptor 2 (NTR2), but not NTR1, where it behaves as a weak partial inverse agonist. In an environmental study, LIVOSTIN 0.05% (levocabastine hydrochloride ophthalmic suspension) instilled four times daily was shown to be significantly more effective than its vehicle in reducing ocular itching associated with seasonal allergic conjunctivitis. After instillation in the eye, levocabastine is systemically absorbed. However, the amount of systemically absorbed levocabastine after therapeutic ocular doses is low (mean plasma concentrations in the range of 1-2 ng/mL). Brand name Livostin is no longer available in the U.S., but generic versions may still be available. Common side effects include burning, stinging, itching, or watering of the eyes, eye irritation or discomfort, blurred vision, dry or puffy eyes, headache, nosebleed, nausea, or fatigue.

Levocabastine (trade name Livo) is a selective second-generation H1-receptor antagonist used for allergic conjunctivitis. Levocabastine binds the G protein-coupled neurotensin receptor 2 (NTR2), but not NTR1, where it behaves as a weak partial inverse agonist. In an environmental study, LIVOSTIN 0.05% (levocabastine hydrochloride ophthalmic suspension) instilled four times daily was shown to be significantly more effective than its vehicle in reducing ocular itching associated with seasonal allergic conjunctivitis. After instillation in the eye, levocabastine is systemically absorbed. However, the amount of systemically absorbed levocabastine after therapeutic ocular doses is low (mean plasma concentrations in the range of 1-2 ng/mL). Brand name Livostin is no longer available in the U.S., but generic versions may still be available. Common side effects include burning, stinging, itching, or watering of the eyes, eye irritation or discomfort, blurred vision, dry or puffy eyes, headache, nosebleed, nausea, or fatigue.

Levamisole (the trade name Ergamisol), an anthelminthic drug with immunological properties. It also has antitumor activity when administered with 5-fluorouracil in patients with Duke's C colorectal carcinoma; however, this use was discontinued. The mechanism of the antitumor effect is unknown but has been postulated to be related to levamisole's immunomodulatory properties. Levamisole can stimulate antibody formation to various antigens, enhance T-cell responses by stimulating T-cell activation and proliferation, potentiate monocyte and macrophage functions including phagocytosis, chemotaxis and increases motility, adherence, and chemotaxis. Levamisole inhibits alkaline phosphatase and possesses cholinergic activity. The mechanism of action of levamisole as an antiparasitic agent, for example, to treat ascariasis, relates to its agonistic activity to L-subtype nicotinic acetylcholine receptors in nematode muscles. In addition, levamisole was studied for preventing relapses of the steroid-sensitive idiopathic nephrotic syndrome (SSINS). It was shown, that alone or in combination with steroids, the drug can prolong the time to relapse and prevented recurrence during one year of treatment. However, these studies also were also discontinued.

Levamisole (the trade name Ergamisol), an anthelminthic drug with immunological properties. It also has antitumor activity when administered with 5-fluorouracil in patients with Duke's C colorectal carcinoma; however, this use was discontinued. The mechanism of the antitumor effect is unknown but has been postulated to be related to levamisole's immunomodulatory properties. Levamisole can stimulate antibody formation to various antigens, enhance T-cell responses by stimulating T-cell activation and proliferation, potentiate monocyte and macrophage functions including phagocytosis, chemotaxis and increases motility, adherence, and chemotaxis. Levamisole inhibits alkaline phosphatase and possesses cholinergic activity. The mechanism of action of levamisole as an antiparasitic agent, for example, to treat ascariasis, relates to its agonistic activity to L-subtype nicotinic acetylcholine receptors in nematode muscles. In addition, levamisole was studied for preventing relapses of the steroid-sensitive idiopathic nephrotic syndrome (SSINS). It was shown, that alone or in combination with steroids, the drug can prolong the time to relapse and prevented recurrence during one year of treatment. However, these studies also were also discontinued.

Azatadine is an antihistamine, which blocks the effects of the naturally occurring chemical histamine in the body. Azatadine is used to treat sneezing; runny nose; itching, watery eyes; hives; rashes; and other symptoms of allergies and the common cold. The antihistamines antagonize those pharmacological effects of histamine, which are mediated through activation of H1- receptor sites and thereby reduce the intensity of allergic reactions and tissue injury response involving histamine release.

Diphenidol, a nonphenothiazinic antiemetic agent used primarily in patients with Meniere disease and labyrinthopathies to treat vomiting and vertigo, is considered to be a relatively safe drug. Since it was first approved in the United States in 1967, this drug has been widely used in Latin America and Asia and has contributed to sporadic suicidal and accidental poisonings in mainland China and Taiwan. The mechanism by which diphenidol exerts its antiemetic and antivertigo effects is not precisely known. It is thought to diminish vestibular stimulation and depress labyrinthine function and as an antimuscarinic agent. An action on the medullary chemoreceptive trigger zone may also be involved in the antiemetic effect. Diphenidol has no significant sedative, tranquilizing, or antihistaminic action. It has a weak peripheral anticholinergic effect. Diphenidol is used to relieve or prevent nausea, vomiting, and dizziness caused by certain medical problems.

Clemizole is a drug in clinical development for the treatment of hepatitis C virus (HCV) infection. Clemizole is a novel inhibitor of TRPC5 channels. Clemizole is an H1 antagonist. Clemizole, an antihistamine drug that was once widely used for treatment of allergic disease, was recently discovered to be a potent inhibitor (IC50, 24 nM) of the interaction between an HCV protein (NS4B) and HCV RNA. Although clemizole was widely used during the 1950s and 1960s, this was before contemporary regulatory requirements were established for new drug development, and there is very minimal information about its pharmacokinetics and metabolism.

Dimetindene (trade name Fenistil; other name dimethindene maleate) is a potent antipruritic antihistamine, characterized by the small size of its effective dose and its rapidity of action. Dimetindene is an antihistamine/anticholinergic that is a selective H1 antagonist. Its effect sets in after 20 to 60 minutes and lasts several hours. Dimetindene drops as well as Dimetindene syrup is particularly indicated in pediatric practice. Dimetindene is indicated as symptomatic treatment of allergic reactions: urticaria, allergies of the upper respiratory tract such as hay fever and perennial rhinitis, food, and drug allergies; pruritus of various origins, except pruritus due to cholestasis; insect bites. Dimetindene is also indicated for pruritus in eruptive skin diseases such as chicken-pox. Dimetindene can be as an adjuvant in eczema and other pruriginous dermatoses of allergic origin.