Domitor (medetomidine hydrochloride) is indicated for use in dogs: for restraint, sedation and analgesia associated with clinical examinations and procedures, minor surgery, pre-anaesthesia and as a premedicant before thiopentone-halothane general a naesthesiaand as a premedicant before general anaesthesia with propofol. In combination with butorphanol for sedation and analgesia, and as a premedicant prior to thiopentone anaesthesia. In cats: for restraint and sedation. Medetomidine is a potent and highly selective alpha2-adrenoreceptor agonist with both central and peripheral activity, and acting both presynaptically and postsynaptically. Its primary effects are sedative and analgesic resulting from its central depressant activity. It has no local anaesthetic properties. Like other compounds of its class there are secondary effects, including bradycardia. Blood pressure is increased but then returns to normal or just below. Body temperature is decreased in a dose dependent manner and intestinal motility is also reduced. The drug has been developed by Orion Pharma. It is currently approved for dogs in the United States, and distributed in the United States by Pfizer Animal Health and by Novartis Animal Health in Canada under the product name Domitor. The marketed product is a racemic mixture of two stereoisomers; dexmedetomidine is the isomer with more useful effects, and is now marketed as Dexdomitor.

Xylazine was developed as an antihypertensive agent. During clinical studies in people xylazine was found to have excessive central nervous system depressant effects and it was subsequently introduced for veterinary use as a sedative, analgesic and relaxant. Xylazine is a potent alpha-2 adrenergic agonist. Xylazine in horses and Cervidae may occasionally cause slight muscle tremors, bradycardia with partial A-V heart block and a reduced respiratory rate. Movement in response to sharp auditory stimuli may be observed.

Atipamezole is a synthetic α2-adrenergic antagonist. It competitively inhibits α2-adrenergic receptors. Atipamezole is indicated for the reversal of the sedative and analgesic effects of Dexdomitor and Domitor in dogs. Adverse reactions: occasional vomiting may occur. At times, a period of excitement or apprehensiveness may be seen in dogs treated with atipamezole. Other effects of atipamezole include hypersalivation, diarrhea, and tremors.

Levlofexidine is R-enantiomer of a α2A adrenergic receptor agonist Lofexidine. Levlofexidine (as a component of Lofexidine) can be used as a short-acting anti-hypertensive but is mostly used to help relieve symptoms of heroin or opiate withdrawal in opiate dependency. Lofexidine is approved in the United Kingdom but is still undergoing clinical trials in the United States. Levlofexidine showed an approximately 9-fold higher affinity than Dexlofexidine for the alpha 2-adrenoceptor-like binding sites in rat brain membranes identified by [3H]-clonidine and was 4 times more potent at displacing [3H]-prazosin from alpha 1-adrenoceptors. The possibility of using lofexidine to treat alcohol addiction withdrawal symptoms has been investigated and has not yet been shown to be an effective treatment.

Proroxan is a non-selective а-adrenoblocker. Proroxan was found to prevent the development of hypertensive crises and improve cerebral bioelectrical parameters in most of hypertensive patients. Proroxan has been used as an antihypertensive and in the treatment of Ménière’s disease, motion sickness, and allergic dermatitis.

Besipirdine is a potential novel first-in-class oral treatment for over active bladder currently in Phase II development, with a mechanism of action clearly different from that of antimuscarinics. It was under evaluation by Aventis up to phase III for Alzheimer’s disease, involving the administration of the compound to over 1500 patients. However, this research has been discontinued. Besipirdine antagonizes alpha-2 and alpha-1 adrenoceptors and inhibits both norepinephrine and serotonin uptake. The most common adverse events were asymptomatic postural hypotension and asymptomatic bradycardia.

Setiptiline Maleate is a tetracyclic antidepressant that has been used in the treatment of depression. It has antihistamine and hypnotic–sedative effects, but almost no anticholinergic effects. It is a weak inhibitor of norepinephrine reuptake in vitro and strongly stimulates the release of central norepinephrine by blocking presynaptic α2-adrenoceptors similar to mianserin. It also acts as a 5-HT2A, 5-HT2C, and 5-HT3 receptor antagonist. Unlike most conventional antidepressants, it has no efficacy as a serotonin reuptake inhibitor. It can induce drowsiness and thirst, but it displays low toxicity. Setiptiline Maleate was launched in 1989 for the treatment of depression in Japan.

Tramazoline is a sympathomimetic drug that is used in the form of tramazoline hydrochloride in nasal decongestant preparations. Tramazoline is an α-adrenergic receptor agonist that inhibits secretion of nasal mucus.

Tolonidine, 2(2-chloro-p-toluidino)-2-imidazoline-nitrate, is a substance chemically related to clonidine. In the anesthetized dog, tolonidine administered i.v. decreased the amplitude of ventricular contractions, reduced aortic blood flow and increased peripheral vascular resistances. In the bivagotomized pithed rat, tolonidine induced a long-lasting increase in blood pressure with no secondary hypotension, thus suggesting peripheral sympathomimetic properties, however, contractions of seminal vesicles in vitro were not obtained. The product proved to have no peripheral sympatholytic or parasympatholytic properties.

Etoperidone is an atypical antidepressant introduced in Europe in 1977. The activity of etoperidone is made mainly by its major metabolite 1-(3'-chlorophenyl)piperazine (mCPP). mCPP binds with different affinity to most of the serotonergic receptors and adrenergic receptors. This metabolite is an agonist of 5-HT2c and an antagonist of 5-HT2a. Part of etoperidone structure contributes to the activity in the α-adrenergic receptors. Etoperidone has been studied for the treatment of depression, tremors in Parkinson, extrapyramidal symptoms and male impotence. It is not certain if it was ever approved and marketed but its current status is withdrawn.