Phenothiazines Meperidine

Further chemical modification of the phenylpiperidine moiety has proven unusually fruitful in producing medicinal agents that affect the central nervous system. First, a series of compounds loosely related to the reversed meperidines produced several drugs with important antipsychotic activity. Further discussion of this pharmacologic activity, often referred to as major tranquilizer activity, will be found in the section on phenothiazines. The group led by Janssen took advantage of the chemistry of the... 

Administration of atropine with meperidine (Demerol), flurazepam (Dalmane), diphenhydramine (Benadryl), phenothiazines, and the tricyclic antidepressants may increase the effects of atropine. There is a decreased effectiveness of haloperidol when administered with the anticholinergic dragp. 

Relief of pain - While subcutaneous administration is suitable for occasional use, IM administration is preferred for repeated doses. If IV administration is required, decrease dosage and inject very slowly, preferably using a diluted solution. Meperidine is less effective when administered orally than when given parenterally. Reduce proportionately (usually by 25% to 50%) when administering concomitantly with phenothiazines and other tranquilizers. 

Drugs that may affect phenothiazines include anticholinergics, beta-blockers, meperidine, paroxetine, ritonavir, and thiazide diuretics. 

Clinically important, potentially hazardous interactions with anticholinergics, arbutamine, belladonna alkaloids, digoxin, disopyramide, meperidine, phenothiazines, procainamide, quinidine, ritodrine, tricyclic antidepressants... 

Full agonists morphine, meperidine, methadone, fentanyl, and heroin Partial agonists buprenorphine, codeine, propoxyphene Mixed agonist-antagonists nalbuphine, pentazocine Antagonists naloxone, naltrexone Phenothiazines chlorpromazine, fluphenazine, thioridazine Others haloperidol, clozapine, risperidone, olanzapine... 

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). 

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