Chlorpromazine dosage

Information about the reduction in chlorpromazine levels caused by lithium is limited, but it would seem to be an established interaction of clinical importance. Serum chlorpromazine levels below 30 nanograms/mL have been shown to be ineffective, whereas clinical improvement is usually associated with levels within the 150 to 300 nanogram/mL range. Thus a fall in levels to below 70 nanograms/mL, as described in one study, would be expected to result in a reduced therapeutic response to chlorpromazine. Therefore the effects of concurrent use should be closely monitored and the chlorpromazine dosage increased if necessary. 

In contrast, another report describes 2 schizophrenic patients taking chlorpromazine 100 mg four times daily who became excessively sedated when they were given cimetidine 400 mg twice daily. The sedation disappeared when the chlorpromazine dosage was halved. When the cimetidine was later withdrawn it was found necessary to give the original chlorpromazine dosage. Chlorpromazine serum levels were not measured. 

Direct information about this interaction seems to be limited to this study. Its clinical importance is uncertain but it seems possible that these antimalarials could cause chlorpromazine toxicity. Monitor the effects of concurrent use closely and anticipate the need to reduce the chlorpromazine dosage. More study is need. See also Drugs that prolong the QT interval + Other drugs that prolong the QT interval , p.257. For mention that promethazine may increase chloroquine levels, see Chloroquine + Promethazine , p.223. 

Class Agent (Brand Name) Dosage Range (mg/day) Chlorpromazine Equivalents (mg) Available Formulations... 

Table 12.2 Percentages of daily dosages of antipsychotic drugs (mg chlorpromazine ...

The dosages of antipsychotic drugs differed markedly between the six sites studied (see Table 12.2). Of note, there were more than 50% of patients in China, Hong Kong, Taiwan, and Singapore taking less than 600 mg chlorpromazine-equivalents... 

Dosage equivalents (expressed as chlorpromazine [CPZ]-equivalent dosages—the equipotent dosage of an FGA compared with 100 mg of CPZ) may be useful when switching from one FGA to another FGA drug (Table 71-1). 

CHLORPROMAZiNE Individualize dosage based on condition severity. Increase dosage until symptoms are controlled, then gradually reduce dosage to the lowest effective maintenance level. Increase parenteral dosage only if hypotension has not occurred. 

Behavioral disorders/Hyperactivity-Generally, do not use chlorpromazine in children younger than 6 months of age except where potentially lifesaving. It should not be used in conditions for which specific children s dosages have not been established. 

Haloperidol is less likely to cause hypotension than chlorpromazine, which has a-adrenoceptor antagonist effects. Both can cause cardiac arrhythmias if used in high dosage or in patients with pre-existing heart disease, or as an idiosyncratic reaction. There have been numerous reports of sudden and unexplained deaths, probably due to cardiac arrhythmia, in patients given chlorpromazine and other neuroleptics. The risk of serious arrhythmia is higher in the obese, and possibly in those of African ancestry. 

Non-aqueous titration methods have been described for the rapid determination of chlorpromazine and its hydrochloride salt by titration with perchloric acid [54]. The titration is performed after the proscribed extraction from suppository, tablet, and ampoule dosage forms is completed. 

The determination of chlorpromazine and other phenothiazines with aqueous NaOH solution in a dimethylformamide medium has been successfully applied to their powder dosage forms [59]. The amperometric determination of chlorpromazine with Ce(S04)2 titrant was also described [60]. The drug was also determined by the titration with sodium lauryl sulfate in an imiscible phase [61]. 

The quantitative determination of chlorpromazine can be performed on the basis of its UV absorption in dilute H2SO4 medium [82]. Chlorpromazine exhibits an E(l%, 1-cm) of 1520 at 278 nm. Chlorpromazine and its sulfoxide were assayed in the injectable dosage form using absorbance values obtained at 240 and 255 nm, respectively [83]. 

In injectable dosage forms, chlorpromazine was diluted with O.IM HCl to a concentration of 0.05 mg/mL, and the absorbance measured at 306 nm [87]. The recovery was found to be 99.37%, and the method proved to be linear in the range of 20-80 pg/mL. There was no interference from ascorbic acid or other stabilizers. 

First-derivative spectrophotometry was used to identify chlorpromazine in the presence of other phenothiazines, while second derivative spectrophotometry enabled the direct determination of chlorpromazine in spiked blood samples [89], In addition, third derivative spectroscopy was used to determine chlorpromazine and its sulfoxide decomposition product in pharmaceutical dosage forms [90]. 

One fluorimetric method for the determination of chlorpromazine hydrochloride in bulk and in various dosage forms begins with the mixing of 0.5 mL of a 60 pg/mL solution with 1 ml of pH 7.2 buffer solution. To this is also added 1 mL of 0.2 mg/mL A/-bromosuccinimide, whereupon the mixture is diluted to 10 mL with methanol. After 30 minutes of reaction time, the fluorescence intensity is measured at 378 nm (excitation at 280 nm). The method was found to be linear over the range of 0.005 -10 pg/mL [145]. 

HPLC has been used by several authors to determine chlorpromazine in various dosage forms and in biological materials [203-239]. Table 10 summarizes some of the HPLC conditions used by various authors. 

A gravimetric assay method based on the precipitation of chlorpromazine hydrochloride in hulk and in various dosage forms has been reported [179]. The method uses a KBrO-KBr mixture in the presence of 15%... 

With the use of major tranquillisers, for example, thioridazine, chlorpromazine, or perphenazine, it is possible to withdraw opiate dependents who are highly motivated. The dosages can be titrated to the degree of clinical symptoms and this can be monitored with key carers through an out-patient clinic. The use of hypnotics should be restricted to short-term use due to their own dependency problems, but they can be a useful addition, particularly in the early phases of the treatment programme. 

Acepromazine is used in cattle, swine, sheep, and goats by parenteral routes at dosages of 0.01-0.22 mg/kg bw. In contrast to some other phenothiazine derivatives such as chlorpromazine and promazine, acepromazine is not used in human therapy. 

Correct answer = D. Carbidopa inhibits the peripheral decarboxylation of levodopa, permitting lower dosage. Chlorpromazine blocks the dopamine receptor site in the brain and therefore blocks the beneficial effects of levodopa. Vitamin B6 enhances the peripheral decarboxylation of levodopa. Dopamine does not itself cross the blood-brain barrier. Phenelzine inhibits the metabolism of norepinephrine and serotonin and may produce a hypertensive crisis. 

Salicylates and anticholinergics are contraindicated in the management of DNOC-poisoned individuals because they may also potentiate the action of DNOC (Haddad and Winchester 1990). Because of the limited animal studies and understanding regarding the interaction between DNOC and proposed antidotes such as 4-methyl-2-thiouracil, chlorpromazine, and vitamins further animal testing would be useful before these dosages are used in cases of human DNOC toxicosis. 

Although high dosages of propranolol (up to 2 g) have been used in combination with chlorpromazine to treat schizophrenia, the combination of propranolol or pindolol with chlorpromazine should be avoided if possible (17). 

Chlorpromazine concentrations were reduced by 36% in smokers (24). Of factors that can affect chlorpromazine concentrations, smoking may be second in importance only to dosage (25). 

Gurovich I, Vempaty A, Lippmann S. QTc prolongation chlorpromazine and high-dosage olanzapine. Can J Psychiatry 2003 48 348. 

Forrest, I. S., Otis, L. S., Serra, M. T., and Skinner, G. C., Passage of 3H-chlorpromazine and 3H-A-tetrahydrocannabinol into the hair (fur) of various mammals, Proc. West. Pharmacol. Soc., 15,83,1972. Sato, H., Uematsu, T., Yamada, K., and Nakashima, M., Chlorpromazine in human scalp hair as an index of dosage history comparison with simultaneously measured haloperidol. Ear. ]. Clin. Pharmacol., 44, 439, 1993. 

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