Radioimmunoassay for fluphenazine in human plasma

Comparative bioavailability of two tablet formulations of fluphenazine dihydrochloride in drug-free psychiatric patients

The comparative bioavailability of a new tablet formulation of fluphenazine dihydrochloride (5 mg) and a reference product (fluphenazine dihydrochloride, Prolixin, 5 mg) was assessed in drug-free psychiatric patients. Twenty-six patients were initially entered in the study, of whom 22 completed the protocol. Each patient received the test (T) and the reference formulation (R) in a balanced two-way crossover design. Plasma concentrations of fluphenazine were monitored over a period of 48 h after drug administration using a sensitive HPLC method. One patient did not show any measurable plasma concentration for one formulation at any sampling time and, therefore, bioavailability was assessed in the remaining 21 patients. All pharmacokinetic parameters showed wide intersubject variation. The maximum plasma concentration (Cmax), time to Cmax, and area under the curve up to the last measurable concentration (AUClast0), infinity (AUCinfinity0), or truncated areas (such as AUC16(0), AUC24(0) were compared by analyses of variance and found not to be significantly different in each case across the formulations. Except for AUC24(0), AUC32(0), and AUC48(0), ANOVA of all other parameters showed a high power (greater than 80%) to detect a 20% difference in the mean value of each bioequivalence parameter between T and R. The two formulations were found to be bioequivalent in that confidence intervals of the mean values of AUCinfinity0, AUClast0, truncated AUCs, or Cmax for T:R ratios were, in each case, well within the acceptable range of 100 +/- 20%.

Pharmacokinetics of haloperidol and fluphenazine decanoates in chronic schizophrenia

In a double-blind comparison of haloperidol decanoate and fluphenazine decanoate given 4-weekly for 60 weeks as maintenance therapy in 38 chronic schizophrenic in-patients, plasma haloperidol, fluphenazine and prolactin levels were measured at regular intervals by radioimmunoassay. After the first injection, the mean plasma haloperidol level was highest at week 1 and fell gradually towards week 4. Mean pre-dose haloperidol levels changed little after week 8. Results suggested an absorption half-life of 4 weeks, although, in three cases steady state was only achieved after 11 monthly injections. Steady state levels of both haloperidol and fluphenazine correlated highly with dose. In two sub-groups observed at steady state, both drugs produced a biphasic pattern of plasma drug concentration between injections, a rapid rise on day 1 followed by stable elevated levels and a gradual return to pre-injection concentration by the end of week 4. In the fluphenazine sub-group there was a second peak on day 7 and a steeper decline, so that the mean area-under-curve in week 4 was 64% of that in week 1. Drug injections at steady state induced an increase in prolactin secretion in all of the fluphenazine sub-group and in half of those receiving haloperidol. Plasma prolactin changes resembled those for drug concentrations, but differences in times of peaks on day 1 resulted in weak correlations. Fluphenazine appeared more potent than haloperidol in provoking prolactin secretion.

Plasma levels of fluphenazine decanoate. Effects of site of injection, massage and muscle activity

Depot neuroleptics are now commonly used for maintenance therapy of schizophrenia. Their physicochemical composition makes them ideal for such use because they are long-acting and show stable blood levels for prolonged periods. Their absorption from the site of injection may, however, be affected by local muscle factors. This paper describes three such factors in relation to fluphenazine decanoate: varying the site of injection; massage of the injection site; and effects of muscular exercise. Our results suggest that fluphenazine pharmacokinetics are not significantly affected by any of these factors.

Plasma levels of fluphenazine and prolactin in psychiatric patients

A total of 100 patients receiving fluphenazine (FPZ) decanoate for at least 12 months (96 schizophrenics and 4 other diagnoses) were investigated for plasma levels of FPZ and prolactin on the day of injection (day 0) and 7 days later (day 7). The plasma FPZ level significantly correlated with the weekly dose of FPZ. The plasma FPZ level per weekly FPZ dose multiplied by 100 (the FPZ ratio) showed a 20-fold variation. The FPZ ratio was significantly higher in the day- and in-patients (hospital-patients) than in out-patients. The plasma prolactin level significantly correlated with the plasma FPZ level but the prolactin to FPZ ratio negatively correlated with the plasma FPZ level. The prolactin to FPZ ratio was lower in the hospital patients than in the out-patients. This may suggest either that the high prolactin to FPZ ratio is an indicator of the therapeutic efficacy of FPZ or that there are at least two biologically distinct subgroups, one with a sharp prolactin response to FPZ, therefore with good prognosis, and another with the reverse direction.

A highly sensitive and specific radioimmunoassay for quantitation of plasma fluphenazine

Antisera of high sensitivity and selectivity were obtained from rabbits immunized with conjugates of hemisuccinylated fluphenazine and porcine thyroglobulin. The antiserum selected (titer 1:6000) for the development of the RIA was obtained after a priming dose and a single iv booster injection three months later. This antiserum had negligible crossreactivity with known available metabolites of fluphenazine (FPZ) and an affinity constant of 2 X 10(10) L/mol. Tritiated FPZ was further purified by HPLC and used as a ligand. The method detects as little as 20 pg/mL of plasma (4 pg/RIA tube) after 1 mL of plasma is extracted. The extraction was performed at a basic pH with heptane: isoamyl alcohol (99:1); the solvent was then back extracted using an acetic phosphate buffer. Recoveries were uniformly high (88.6 +/- 2.1%), and this aqueous buffer extract was used directly in the RIA procedure. The assay has intra- and interassay coefficients of variation of 5.8 and 8.2%, respectively, in a plasma concentration of 95 pg/mL. Results using this procedure have been cross validated against an HPLC procedure (r = 0.952, slope = 1.032, intercept = 0.009, n = 18). In a single-dose FPZ study (10 mg, po), plasma FPZ levels in 25 normal volunteers could be monitored greater than 48 h post dose. Single plasma level profiles, after an initial injection of 12.5 mg of FPZ decanoate, could be measured greater than 36 d, and, in some cases, up to 100 d post dose.

Haloperidol decanoate v. fluphenazine decanoate as maintenance therapy in chronic schizophrenic in-patients

In a double-blind study of 38 chronic schizophrenic in-patients, haloperidol decanoate was compared with fluphenazine decanoate as maintenance therapy over 60 weeks. Both drugs were given by injection at 4-week intervals. Haloperidol and fluphenazine were assumed to be equipotent; the mean starting dose of the former was 127 mg and of the latter 106 mg. The number of withdrawals over 60 weeks was similar in both groups but relapses, strictly defined, were significantly more frequent in the haloperidol group. When patients were switched to haloperidol, Parkinsonism diminished more quickly than in the fluphenazine group, but after 60 weeks there was no difference in severity in the two drug groups. The higher relapse rate and the quicker reduction in Parkinsonism in the haloperidol group might be due to a misjudgement in equivalent doses of the two drugs. Plasma haloperidol steady state levels were reached in most patients by 8-12 weeks. Plasma neuroleptic and prolactin levels, week-by-week systemic drug availability and Parkinsonism showed less variation between injections with haloperidol than with fluphenazine.

Schizophrenia with good and poor outcome. I: Early clinical features, response to neuroleptics and signs of organic dysfunction

Seventy-seven patients with diagnosis of schizophrenia (62) or schizoaffective disorder (15) were studied 2-20 years since onset of illness, when in a stable condition. The investigation included clinical assessment, measurement of plasma concentrations of neuroleptics and prolactin, computed tomography brain scan, neuropsychological and neurological examination. Outcome of illness was classified according to the presence of chronic psychiatric symptoms and social impairment, and response to neuroleptics according to the effect of treatment in the most recent psychotic episode. Neither outcome nor response to neuroleptics was related to duration of illness. The groups with good and poor outcome differed in premorbid adjustment, age at onset and symptoms of the initial episode, but not in drug bio-availability or prolactin response. Large cerebral ventricles and cognitive impairment, but not neurological 'soft' signs, were associated with unfavourable outcome. The three measures of organicity were not inter-related. No clinical differences were found between chronic patients with and without signs of organic dysfunction. The findings suggest that schizophrenia with good and unfavourable outcome may be separate sub-types. However, the role of organic factors in the latter group remains unclear.

Plasma levels of fluphenazine during fluphenazine decanoate treatment in schizophrenia

The authors measured plasma fluphenazine levels in 20 schizophrenic patients receiving 25 or 50 mg fluphenazine decanoate (FPZ-D) by IM injection every 2 weeks. The plasma levels were determined by a sensitive gas-liquid chromatographic (GLC) assay with a nitrogen detector device developed in their laboratory. Using this chemical assay method, they replicated the finding of a sharp initial plasma peak within 24 h after the injection followed by a low but rather stable plasma level as previously reported by nonchemical assay methods. The interval plasma levels (averages of day 4-10 after injection) ranged from 0.17-0.61 ng/ml in 10 patients who received 25 mg; and 0.20-0.93 ng/ml in 7 patients who received 50 mg FPZ-D every 2 weeks. This four-fold variation in plasma levels during FPZ-D injection was smaller than previously reported levels achieved with oral antipsychotic drug treatment. Based on the study of plasma levels achieved with FPZ-D injection and oral FPZ-H (fluphenazine HC1) in 6 patients, the dosage requirement of FPZ-D appeared to be difficult to predict from the oral dosage of FPZ-H in the same patient. Two weeks past injection, fluphenazine was undetectable in approximately half the samples with the GLC method. Thus, radioimmunoassay or radioreceptor assay, which also measures metabolites, might be more suitable for the study of plasma levels in patients receiving FPZ-D injection.

Within-individual variation in steady state plasma levels of different neuroleptics and prolactin

Eleven male chronic schizophrenics were given, serially, oral pimozide, fluphenazine, and flupenthixol; the two latter were also given intramuscularly as decanoates in oil. Oral haloperidol was given before and after each drug. Analysis of variance of steady state plasma levels of the different neuroleptics showed considerable within-individual variation in such levels, probably due to differences in absorption and metabolism and between routes of administration. The findings suggest that if a patient fails to respond to one neuroleptic, there may be good pharmacokinetic reasons for switching him to another belonging to a different group, or for giving the same neuroleptic by a different route of administration. The study also showed that previous administration of one neurololeptic may influence the steady state level of another. The various neuroleptics produced different effects on plasma prolactin levels.

Blood and plasma kinetics of cis(Z)-clopenthixol and fluphenazine in psychiatric patients after intramuscular injection of their decanoic esters

Whole blood and plasma concentrations of active neuroleptic drugs were measured in eight schizophrenic outpatients who had received cis(Z)-clopenthixol decanoate in Viscoleo or fluphenazine decanoate in sesame oil by intramuscular injection. Whole blood and plasma concentrations were very similar, though there was a slight tendency for blood concentrations to be higher than plasma concentrations. Maximum concentrations appeared at 1 week after administration of cis(Z)-clopenthixol decanoate, whereas the highest concentrations after fluphenazine decanoate were seen at the end of the 3-week dosage interval. Some between-individual variation and a limited within-individual variation was seen.

Subnanogram determination of fluphenazine in human plasma by gas chromatography mass spectrometry

A new gas chromatographic mass spectrometric procedure for the quantitation of fluphenazine in plasma is described. The method relies on the selected ion monitoring of fluphenazine (m/z 406.1563) and perphenazine (m/z 372.1299), the internal standard, after extraction from plasma with 5% isopropanol in n-pentane. Interferences by plasma constituents such as cholesterol are avoided by including an n-hexane wash. This wash step reduced the recovery of fluphenazine and to a greater extent perphenazine, however, it yielded an organic solution relatively free of any peaks with interfering ions. Prior to gas chromatographic mass spectrometric analysis the silyl derivatives of fluphenazine and perphenazine are prepared using N,O-bis(trimethyl-silyl)acetamide. This procedure allows for the quantitation of as low as 78 pg of fluphenazine per ml of plasma using 2.0 ml plasma aliquots with a coefficient of variation of 4.6%. The high specificity and sensitivity demonstrated by this method allows for the first time the monitoring of plasma concentrations of fluphenazine up to 32 h following a single oral dose of 5 mg of the drug.

Determination of fluphenazine in plasma by high-performance thin-layer chromatography

Determination of fluphenazine in blood plasma by in situ fluorescent detection after separation by high-performance thin-layer chromatography is described. Enhancement of fluorescent emission of the drug is accomplished by exposure to UV light in the presence of paraffin oil which permits a limit of detectability of approximately 0.1 ng/ml in blood plasma. Thirty samples or more can be processed in a 7-h period with excellent precision (less than 3% relative standard deviation at 2.5 ng/ml). Investigation of extraction procedures, chromatographic conditions, photodevelopment, and fluorescent detection are described.

A depot neuroleptic withdrawal study neurological effects

A double-blind withdrawal trial in 41 chronic schizophrenic outpatients was carried out over 6 months. Depot neuroleptics (fluphenazine decanoate or flupenthixol decanoate) were compared with placebo to evaluate neurological side effects during continued therapy and during withdrawal. The drugs were significantly more effective than placebo in preventing relapse and rehospitalization. In the placebo group 62% relapsed compared to 27% in the drug group. A difference was observed in the occurrence of extrapyramidal symptoms (EPS) between the neuroleptics in the study. Akathasia was observed in 9/38 (23.7%) cases, significantly more frequent in the fluphenazine decanoate group. Tardive dyskinesia (TD) was observed in six cases (15.8%); four cases existed at the start of the study and two others were observed after 3-6 weeks of withdrawal. There was no relation between TD symptoms and relapse. There was a significant decrease in the EPS scores during the placebo treatment and also a significant weight decrease.

Kinetics of oral fluphenazine disposition in humans by GC-MS

The disposition of fluphenazine was investigated in six healthy volunteers following oral administration (5 mg). Using a sensitive and specific GC-MS procedure plasma fluphenazine concentrations were measured up until 32 h after drug administration. Peak plasma concentrations varied widely (range: 0.26-1.06 ng/ml) and were observed at 2.8 +/- 0.5 h following fluphenazine administration. The apparent terminal elimination half-life of fluphenazine was 33.1 +/- 8.1 h. The area under the plasma concentration-time curve differed widely between subjects (range: 7.1-28.6 ng/ml h) suggesting large interindividual differences in the extent of fluphenazine presystemic elimination.

Variation in oro-facial tardive dyskinesia during depot antipsychotic drug treatment

Oro-facial (tardive) dyskinesia, occurring in patients on long-term antipsychotic (dopamine antagonist) medication, can be suppressed temporarily by increasing the drug dose. Lowering the dose can exacerbate the condition. In patients receiving regular fluphenazine decanoate (FPZ) and flupenthixol decanoate (FPT) injections, characteristic profiles of the fluctuations in plasma level concentrations, occurring during the injection interval, have been demonstrated. The possible effects of these relatively predictable plasma level changes on the severity of oro-facial dyskinesia, and parkinsonism, were investigated. Regular assessment of oro-facial dyskinesia throughout the injection interval was carried out in six patients receiving FPZ and two patients receiving FPT. In both groups, changes were observed in the severity of oro-facial dyskinesia consistent with the expected effects of drug level fluctuations. The main implication of this finding is that, in investigations of tardive dyskinesia in patients receiving depot medication, ratings should be carried out at a standard time relative to injections.

Dose-response relationships of perphenazine in the treatment of acute psychoses

A group of 26 acute psychotic patients received continuous oral treatment with perphenazine for a period of 5 weeks. Once-weekly blood samples were drawn for measurements of perphenazine levels and, simultaneously, the therapeutic outcome was registered. Another 26 acute psychotic patients received continuous oral treatment with perphenazine for a period of up to 4 weeks. A single blood sample was drawn and the perphenazine concentration was related to the appearance of extrapyramidal side effects. The following conclusions were made: (1) a high risk of provoking extrapyramidal side effects was associated with plasma levels of perphenazine above 3 nmol/l; (2) plasma levels below 2 nmol/l were associated with a poor therapeutic outcome; (3) a 'therapeutic window' between 2 and 3 nmol/l gives maximal therapeutic effect with a low risk of provoking extrapyramidal side effects.

A depot neuroleptic withdrawal study. Plasma concentration of fluphenazine and flupenthixol and relapse frequency

A double-blind withdrawal trial in 41 chronic schizophrenic outpatients was carried out during 6 months. Depot neuroleptics (fluphenazine decanoate or flupenthixol decanoate) were compared with placebo to evaluate clinical and neurological effects during continued therapy and during withdrawal. The drugs were significantly more effective than placebo in preventing relapse and rehospitalization. In the placebo group 62% relapsed compared to 27% in the drug group. There was a weak and nonsignificant tendency to a higher relapse frequency in the flupenthixol group compared to the fluphenazine group. After withdrawal for 6 months, plasma levels for fluphenazine were detectable. Plasma levels for flupenthixol were not detectable after 9 weeks of withdrawal. The differences in the plasma levels may possibly explain the difference in relapse rate between the two depot neuroleptics. Furthermore, it was found that the patients who relapsed during fluphenazine treatment had a significantly lower plasma level of the drug than patients who did not relapse during treatment. The results from this study provide some information on the therapeutic levels of fluphenazine and flupenthixol in schizophrenic patients.

Radioimmunoassay for trifluoperazine in human plasma

1 A new sensitive and rapid radioimmunoassay procedure for the determination of the plasma concentrations of the neuroleptic drug trifluoperazine is described. 2 The antiserum developed for trifluoperazine cross-reacted with N-desmethyltrifluoperazine and 7-hydroxytrifluoperazine to the extent of 26 and 24% respectively but its cross-reactivity with commonly co-administered tricyclic antidepressants and antianxiety agents tested was negligible. 3 The assay, based on the above antiserum, enabled the quantitation of 50 pg of the drug in 200 microliters of plasma with a coefficient of variation of about 2% and therefore should be applicable for singly dose pharmacokinetic and bioavailability studies. It should be applicable to therapeutic monitoring of the drug in patients.

Plasma levels of perphenazine (Trilafon) related to development of extrapyramidal side effects

Thirteen acute psychotic patients received continuous oral treatment with perphenazine for a period of 8 weeks. Blood samples for quantification of perphenazine, perphenazine sulphoxide and prolactin were drawn twice weekly. Simultaneously, the therapeutic outcome and the degree of extrapyramidal side effects were recorded. The following conclusions were made: 1. In accordance with results achieved in one of our earlier investigations, a high risk of provoking extrapyramidal side effects was associated with plasma levels of perphenazine exceeding about 3 nmol/l. 2. An excellent therapeutic outcome was associated with plasma concentrations of perphenazine above 1.5 nmol/l. 3. Plasma concentrations of perphenazine and prolactin were poorly correlated to each other (R = 0.49). 4. A significant correlation (R = 0.85) was shown between the scores for the Brief Psychiatric Rating Scale and the Comprehensive Psychopathological Rating Scale.

Radioimmunoassay for perphenazine in human plasma

1 A new sensitive, specific and rapid radioimmunoassay procedure for the determination of plasma concentrations of the neuroleptic drug perphenazine is described. 2 The antiserum developed for perphenazine did not cross-react with most of the major metabolites of perphenazine nor the tricyclic antidepressants and antianxiety agents commonly co-administered with the drug. 3 The assay, based on the above antiserum, enabled the quantitation of 50 pg of the drug in 200 microliters of plasma with a coefficient of variation of about 8% and therefore should be applicable for single dose pharmacokinetic studies, as well as therapeutic monitoring of the drug in patients.

Intermittent pimozide versus fluphenazine decanoate as maintenance therapy in chronic schizophrenia

In a double-blind trial, 34 male chronic schizophrenic day-patients or in-patients in a hostel ward continued on fluphenazine decanoate given mostly once fortnightly or were switched to pimozide, given on four days each week. Over nine months relapse rates were similar for both groups, and while fewer patients on pimozide were prescribed antiparkinsonian drugs one quarter developed buccolingual masticatory dyskinesia. Plasma pimozide levels suggested satisfactory drug compliance. Average plasma prolactin levels were within the normal rage for untreated men in one quarter of non-relapsing patients on pimozide and three quarters on fluphenazine.

Long-term fluphenazine decanoate maintenance dosage requirements of chronic schizophrenic patients

Forty-seven schizophrenic out-patients, who were satisfactorily maintained on a depot injection of fluphenazine decanoate, and who received the injection every 28 days, were progressively withdrawn from medication by increasing the time interval between injections while maintaining the amount of of drug per injection. The rate of reduction varied with each patient depending on various factors such as environmental stress considerations, and the patient's wishes. Finally three injections at 8-weekly intervals were given before complete withdrawal. The follow-up period was 23.7 months with a standard deviation of 1.9. A relapse rate of 80% was found, 25 patients relapsing during the withdrawal phase and 22 patients after the drug had been completely withdrawn.

Clopenthixol and flupenthixol depot preparations in outpatient schizophrenics. III. Serum levels

Serum concentrations of clopenthixol and flupenthixol have been determined during a four weeks dosage interval in patients treated with intramuscular injections of clopenthixol decanoate or flupenthixol palmitate in Viscoleo. Maximal drug levels were attained by the end of the first week after injection of either preparation. A period of exponential decline was then recorded. The half-lives were estimated to 19 days for clopenthixol and 17 days for flupenthixol. These half-lives most likely refer to the rate of release from the oil depot and not to elimination of drug. The mean ratio between maximal and minimal drug levels was 2.5 for clopenthixol and 3.7 for flupenthixol. Systemic clearance was estimated to about 0.7 l/min and 0.5 l/min, respectively. Significant correlation was found between the administered doses and recorded serum levels, between doses and estimated areas under the serum concentration curves, and also between areas and drug levels. The data indicate more limited individual variability than that seen with other psychotropic drugs, given orally. The study clearly demonstrates, that significant serum levels of active drug is maintained throughout the dosage interval by intramuscular injection of clopenthixol decanoate or flupenthixol palmitate in Viscoleo every fourth week.

Plasma fluphenazine and prolactin levels in schizophrenic patients during treatment with low and high doses of fluphenazine enanthate

The relationship between plasma prolactin (PRL) and drug levels in patients receiving neuroleptic drugs is of special interest in view of evidence that the PRL elevation induced by these drugs reaches its maximum at sub-therapeutic doses. Plasma PRL and fluphenazine (FPZ) levels were measured by radioimmunoassay (RIA) in each of 11 chronic schizophrenics (nine men, two women) during two 4-week periods of treatment with FPZ enanthate at a "High Dose' (250 mg per week) and a "Low Dose' (12.5 mg per week) given in random order. Plasma PRL levels were above normal in 9 of 11 subjects during the last week of Low Dosage. High Dosage resulted in PRL levels significantly greater than found during Low Dose treatment in 9 of 11 patients. Thus the PRL response had not reached its "ceiling" during Low Dosage in most patients. A significant correlation between PRL and FPZ levels was found in seven subjects; evidence that immunoreactive FPZ levels relate to an effect caused by blockade of dopamine receptors. The plasma FPZ pattern between injections during week 1 of Low Dosage was remarkably stable; High Doses produced an initial drug peak at 1--2 h and a secondary peak occurring on days 2--3 followed by a return to preinjection levels by day 7.

The evaluation of a radioimmunoassay for phenothiazines and thioxanthenes using an iodinated tracer

Antisera have been raised in rabbits to the immogen 2-trifluoromethylphenothiazine-10-beta-propionate bovine serum albumin. An [125I]-labelled tyrosine methyl ester derivative of the immunogen precursor has been synthesised and used with the antisera to develop a simple, precise and sensitive radioimmunoassay for phenothiazines and thioxanthenes bearing 2-trifluoromethyl substituents. The assay can detect 0.4 ng/ml of fluphenazine, trifluorperazine or (Z)-flupenthixol in 100 microliter of human serum without interference from their sulphoxide or 7-hydroxylated metabolites. An acceptable correlation between this assay and an established fluphenazine radioimmunoassay using commercial [3H]fluphenazine has been obtained for plasma samples.

Plasma fluphenazine levels by radioimmunoassay in schizophrenic patients treated with depot injections of fluphenazine decanoate

1 Using a radioimmunoassay, plasma fluphenazine (FPZ) concentrations were examined in 33 schizophrenic patients during 38 intervals between injections of FPZ decanoate. Doses ranged from 12.5 to 150 mg and intervals from 1 to 5 weeks. At least three blood samples were taken between injections from each subject; also in 26 subjects additional samples were taken during the first 24 h post-injection. 2 FPZ was measurable in all plasma samples. 3 Each injection was followed by a rapid rise in plasma FPZ concentration to a maximum at 1-8 h. The height of this peak varied considerably. Within the next 12-36 h plasma FPZ fell to a level slightly above that found before injection and then remained stable until the next injection, thus confirming the steady release of FPZ from the depot over this period. 4 For the group, dose and mean plasma FPZ levels correlated strongly. 5 Despite this, there was a four-fold variation in plasma FPZ concentration among subjects receiving the same dose. 6 The FPZ level on the last day of an interval between injections was a satisfactory estimate of the mean FPZ level for the interval. 7 In one subject examined in this way, a positive correlation was found (r = 0.76) between plasma FPZ (by radioimmunoassay) and plasma prolactin levels.

Kinetics of fluphenazine after fluphenazine dihydrochloride, enanthate and decanoate administration to man

1 Fluphenazine (1,2-ethanol 14C) was administered to seven human subjects as the dihydrochloride and as the enanthate and decanoate esters. 2 The subjects had previously been treated with fluphenazine injections for at least 6 months. 3 Fluphenazine was separated from its radioactive metabolites by selective solvent extraction. Plasma concentrations were measured for up to 21 days after dosing. 4 The preparations showed differences in peak concentrations, times of the peaks and half-times of the elimination phase. The longest half-times occurred with the decanoate and the shortest with the dihydrochloride. 5 It is postulated that the differences in kinetics relate principally to the release of the compound from the site of injection. 6 There was no evidence for presence of the esters in plasma, urine or faeces.