Phenothiazine antihistaminic

Closed-angle glaucoma Topical anticholinergics Topical sympathomimetics Systemic anticholinergics Heterocyclic antidepressants Low-potency phenothiazines Antihistamines Ipratropium... 

Synthesis of chlorpromazine, a very sedating phenothiazine antihistamine. ... 

Uses Allergic Rxns itching Action Phenothiazine antihistamine serotonin antagonist Dose Adults. 4-20 mg PO qSh max 0.5 mg/kg/d Feds. 2-6 y 2 mg bid-tid (max 12 mg/24 h) 7-14 y 4 mg bid-tid in hepatic impair Caution [B, ] BPH Contra Neonates or <2 y NAG BOO acute asthma GI obst Disp Tabs, syrup SE Anticholinergic, drowsiness Interactions T Effects Wf CNS depressants, MAOIs, EtOH X effects OF epi, fluoxetine EMS Use other CNS depressants w/ caution concurrent EtOH use can T CNS depression higher epi doses may be needed if used OD May cause mood changes, Szs, CNS depression, or CNS stimulation symptomatic and supportive... 

Cyproheptadine resembles the phenothiazine antihistaminic agents in chemical structure and has potent H receptor-blocking as well as 5-HT2-blocking actions. The actions of cyproheptadine are predictable from its histamine and 5-HT receptor affinities. It prevents the smooth muscle effects of both amines but has no effect on the gastric secretion stimulated by histamine. It also has significant antimuscarinic effects and causes sedation. 

Drug-induced photosensitivity reactions are divided into phototoxicity (a nonimmunologic reaction) and photoallergic reactions (an immunologic reaction). The latter form is far less common. Medications associated with photosensitivity reactions include fluoroquinolones, nonsteroidal antiinflammatory drugs, phenothiazines, antihistamines, estrogens, progestins, sulfonamides, sulfonylureas, thiazide diuretics, and tricyclic antidepressants. 

Some antihistaminics, such as promethazine and diphenhydramine, have local anesthetic properties. They may be used substitutively in patients who are allergic to both amide and ester types of local anesthetics. Some phenothiazine antihistaminics, such as promethazine, have alpha-adrenergic blocking effects. Therefore, like phenothiazine neuroleptics, promethazine may cause orthostatic hypotension. 

Additive effects are likely after concomitant use of nortriptyline with CNS depressants, including alcohol, analgesics, barbiturates, narcotics, tranquilizers, and anesthetics (oversedation) atropine and other anticholinergic drugs, including phenothiazines, antihistamines, meperidine, and antiparkinsonian agents (oversedation, paralytic ileus, visual changes, and severe constipation) and metrizamide (increased risk of convulsions). 

Trimeprazine, a phenothiazine antihistaminic possessing antipruritic activity (25 mg p.o. q.i.d.), is used in pruritis. 

Thus, the significant point of difference between the phenothiazine antihistaminics and the phenothiazine antipsychotics is that the latter should have an unbranched propyl chain. However, there are two most important aspects that are most essential for the phenothiazine antihistaminics, namely ... 

The two aromatic groups noted in several of the classes of antihistamines can be connected to each other through additional atoms (e.g., heteroatoms like sulfur or oxygen) or through a short, 1- or 2-carbon chain. They have a general structure shown in Figure 37.11. The earliest potent tricyclic antihistamines (Table 37.7) were phenothiazines (Y=S, X=N). The phenothiazine antihistamines contain a 2- or 3-carbon, branched alkyl chain between the nonbasic phenothiazine nitrogen and the aliphatic amine. They differ from the antipsychotic phenothiazine derivatives in which the chain usually is three... 

Knowledge of the chemistry of local anaesthetics also helps in finding possible substitutes, e.g., the replacement of an ester by an amide agent which neither cross-reacts, nor is likely to cause allergy by itself. Many other compounds have local anaesthetic properties, and may be thought of as potential alternatives, e.g., certain phenothiazine antihistamines and propranolol (the jS-adrenoceptor blocker). 

Nitrogen-linked ethylenediamines Oxygen-linked ethanolamines Carbon-linked alkylamines Phenothiazine antihistamines Cyclizines (piperazines) Piperidines Miscellaneous... 

Although topical phenothiazine antihistamine preparations such as promethazine hydrochloride (Phenergan) cream are no longer used in the United States, such topical antihistamine preparations are still widely used in Europe. Individuals who have become sensitized by such topical phenothiazine antihistamines often suffer a flare of the dermatitis when a phenothiazine antihistamine is taken, i.e., a systemic eczematous contact dermatitis. In addition, many individuals acquire allergic sensitization to various phenothiazine drugs which show cross-reactions with the phenothiazine antihistamines. Table 6 lists the phenothiazine antihistamine compounds. 

The phenothiazine drugs listed in Table 7 are all capable of cross-reacting with the phenothiazine antihistamines, and all of these compounds are potential photosensitizers (Lewis and Sawicky 1955). Often a photoallergic reaction occurs in combination with the allergic eczematous contact dermatitis. The systemic administration of the phenothiazine drugs shown in Table 7 may produce an eczematous contact dermatitis medicamentosa in individuals sensitized by such topical exposure. Cross-reactions readily take place between these phenothiazines and the related antihistamines (Mitchell and Ongley 1972). 

Medical and nursing personnel who inject these phenothiazine drugs or who handle phenothiazine tablets which are given to patients, and those who come into contact with the compounds in the pharmaceutical industry readily acquire allergic eczematous contact dermatitis of the hands from such exposure the dermatitis may flare when a phenothiazine antihistamine is given (Calnan et al. 1962). Since chlorpromazine, in particular, is excreted almost unchanged in the urine, sensitized nurses and orderlies who handle unwashed linen may experience flares. 

The same phenothiazines or closely related compounds which are used as psychotropic drugs or as sedatives in humans are used by veterinarians and farmers as insecticides and anthelmintics for animals and birds. Table 8 lists the commercial phenothiazine insecticides and wormers used by veterinarians. Many individuals in these professions have acquired allergic contact dermatitis, photoallergic reactions, or both by spraing such phenothiazines for insect control or feeding these compounds as wormers. Such individuals must avoid using phenothiazine antihistamines because of the likelihood of producing flares of the phenothiazine dermatitis. 

Ethch1orvyno1 Acetylsalicylic acid. Paracetamol, Propoxyphene Diphenylhydantoin Benzodiazepines, Meprobamate, Tricyclic antidepressives, Phenothiazines, Antihistamines Alcohols, Narcotics, Chloral hydrate, Hezapropymate, Fe, Li Phthalates and Adipate, and further plasticizers and vacutainer contents. Fatty acids and -esters. Cholesterol, Squalene (in saliva)... 

In 1973 Worz described a case of a 60-year-old woman in whom oral dyskinesia developed after prolonged use of a non-phenothiazine antihistamine mehydro-lin(25 ). Thach et al. 9 ) described 2 cases of oral facial dyskinesia associated with prolonged use of antihistamine decongestants, which must be briefly discussed here, since the drugs involved are very widely used, often for trivial indications. 

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