A comparison of the covalent binding of clozapine and olanzapine to human neutrophils in vitro and in vivo

Covalent binding of a reactive metabolite of clozapine to neutrophils or their precursors is thought to play a role in the development of clozapine-induced agranulocytosis. Immunoblotting studies with an anti-clozapine antiserum detected covalent binding of clozapine to human neutrophils in vitro when HOCl was used to generate clozapine reactive metabolite (major clozapine adducts of 31, 49, 58, 78, 86, 126, 160, and 204 kDa). In addition, incubating neutrophils with clozapine and H2O2 (major clozapine adducts of 49 and 58 kDa) or clozapine, H2O2, and human myeloperoxidase (major clozapine adducts of 31, 49, 58, and 126 kDa) also resulted in covalent binding of clozapine to the neutrophils. The covalent binding of clozapine to neutrophils was inhibited by extracellular glutathione when HOCl, but not H2O2 was used to generate reactive metabolite. We found that the antiserum against clozapine also recognized olanzapine, an antipsychotic drug that forms a similar reactive metabolite to clozapine but has not been associated with induction of agranulocytosis. Repeating the in vitro experiments with olanzapine revealed that the major olanzapine-modified polypeptides had molecular masses of 96, 130-170, and 218 kDa. Only relatively low levels of 31, 49, and 58 kDa adducts were observed. Clozapine-modified polypeptides also were detected in neutrophils from patients being treated with clozapine. A major 58-kDa clozapine-modified polypeptide was detected in all patients tested. In contrast, no drug-modified polypeptides were detected in neutrophils from patients taking olanzapine. The differences in covalent binding exhibited by the two compounds and, in particular, the lack of olanzapine binding to human neutrophils in vivo may help to explain the difference in toxicity of these two drugs.     

Resolution of metastatic calcification in the paws of a cat with successful dietary management of renal hyperparathyroidism

BACKGROUND: Clozapine is an atypical antipsychotic drug indicated for patients with schizophrenia in whom traditional antipsychotic drugs (such as haloperidol or the phenothiazines) are ineffective, or in those who experience intolerable adverse effects. Clozapine treatment may be complicated by the development of life-threatening agranulocytosis, so regular haematological monitoring is required. OBJECTIVES: To determine the incidence of clozapine-induced agranulocytosis in Australia and the importance of monitoring white blood cell counts in patients treated with clozapine. DESIGN: Review of haematological monitoring for the first three years (June 1993-July 1996) of operation of the Australian Clozaril (clozapine; Novartis Australia) Patient Monitoring System (CPMS) central database. RESULTS: In the 4061 patients prospectively monitored by the CPMS, the incidence of agranulocytosis, neutropenia and leukopenia combined was 2.6% (n = 104); the incidence of agranulocytosis was 0.9% (n = 37). So far there have been no deaths in Australia from the complications of clozapine-induced agranulocytosis. CONCLUSION: The incidence of agranulocytosis and neutropenia associated with clozapine use in Australia is similar to that in the rest of the world. Monitoring the white blood cell counts of patients being treated with clozapine ensures minimal risk to patients who develop agranulocytosis.     

Apoptosis of neurons in the vestibular nuclei of adult mice results from prolonged change in the external environment

Five patients with non-cytotoxic drug-induced agranulocytosis were treated with recombinant human granulocyte-colony-stimulating factor (rh-G-CSF). The drugs involved were dipyrone, captopril, clozapine and carbimazole. Bone marrow examination revealed a depleted granulopoiesis with normal erythro- and megakaryocytopoiesis. After discontinuation of the suspected drug, rh-G-CSF was administered daily at 5 microg/kg subcutaneously. The neutrophil counts were recovered between day 6 and 12 and patients were discharged from hospital shortly afterwards. Compared to data from the literature, the neutrophil recovery appeared to be faster than expected without the use of haematopoietic growth factors. In conclusion, rh-G-CSF at a standard dose of 5 microg/kg seems to be an effective treatment for drug-induced agranulocytosis.     

Allogeneic cell therapy with donor peripheral blood cells and recombinant human interleukin-2 to treat leukemia relapse after allogeneic bone marrow transplantation

Allogeneic bone marrow transplantation (BMT) is the only effective treatment for hematologic malignancies resistant to conventional chemotherapy. Until recently, no cure existed for patients who relapsed post-BMT. We present our long-term observations on remission induction, after relapse post-BMT, by allogeneic cell therapy (allo-CT) and the feasibility of remission induction in allo-CT-resistant patients by activation of antileukemia effector cells with recombinant human interleukin-2 (rhIL-2) in vitro and in vivo. The longest observation of successful allo-CT (event-free survival, greater than 8 years) was made in a patient with resistant pre-B lymphoblastic leukemia who received infusions with graded increments of donor (female) peripheral blood lymphocytes (PBL) as soon as bulky hematologic and extramedullary relapse was noticed early post-BMT. The patient is currently without evidence of residual host (male) cells as determined by polymerase chain reaction (PCR). Of 17 patients with acute and chronic leukemia in relapse after BMT, 10 were reinduced into complete remission. Four patients with cytogenetic relapse responded to allo-CT alone, while five of six patients with overt hematologic relapse responded only after additional activation of donor with rhIL-2. Allo-CT can, therefore, successfully reverse chemoradiotherapy-resistant relapse of both acute and chronic leukemia. Moreover, in patients resistant to donor lymphocyte infusion, remission can be accomplished by additionally activating donor PBL in vitro and/or in vivo with rhIL-2. Based on our observations, after BMT, allo-CT should be considered the treatment of choice for patients with hematologic malignancies resistant to conventional anticancer modalities. Allogeneic activated cell therapy (allo ACT) should be considered for patients with tumor cells resistant to allo-CT. Although allo-CT, followed if indicated by allo-ACT, can be effective for patients with overt hematologic relapse, reversal of persistent minimal residual disease or documented molecular/cytogenetic relapse early after BMT may also be considered as a possible indication for allo-CT.     

Metabolism and bioactivation of clozapine by human liver in vitro

The metabolism of clozapine by human liver has been investigated in vitro. Irreversible protein-binding and conjunction with model nucleophiles have been used as markers for bioactivation of clozapine, while stable metabolite formation has been assessed using radiometric HPLC. In all nine liver microsomal preparations investigated, clozapine was extensively metabolized to the stable products desmethylclozapine (range 19%-27.2%), N-oxide (1.5-20.5%) and three polar metabolites (0-20.8%), and was bioactivated to a protein-reactive metabolite (0.6-2.1%). The CYP2D6 genotype did not influence the capacity of the livers to form these metabolites. All metabolic pathways were inhibited by ketoconazole, indicating the involvement of the cytochrome P450 enzymes. Isozyme-selective inhibitor studies demonstrated that whereas demethylation was performed by CYP1A2, N-oxidation and chemically reactive metabolite formation were dependent upon multiple forms of P450. The N-oxide was readily reduced back to clozapine in the presence of NADPH, this conversion being inhibited by ascorbic acid. Glutathione (1 mM) decreased covalent binding by 70%. The amount of putative adduct formed in the presence of glutathione (13.4 +/- 0.9%) was much greater than the covalent binding (mean 1.1 +/- 0.2%). The bioactivation of clozapine was, like the N-oxidation of clozapine, a reversible process. In summary, our results indicate clozapine undergoes extensive metabolism by human liver to both stable and chemically reactive metabolites, the formation of which is catalyzed by the cytochrome P450 enzymes. The role of the reactive metabolite, which may be a free radical, in the pathogenesis of clozapine agranulocytosis and hepatotoxicity requires further study.     

Videolaparoscopic access in the surgical treatment of colorectal cancer: critical analysis]

Clozapine was approved by the U.S. Food and Drug Administration in 1989 for treatment of severely ill schizophrenic patients. It has activity against both the positive and negative symptoms of schizophrenia, which has made it an alternative to traditional antipsychotic medications such as haloperidol. However, clozapine must be used cautiously due to its side effect profile. These side effects include agranulocytosis, seizures, and cardiorespiratory symptoms. We report the case of a patient who developed polyserositis (pericardial effusion, pleural effusion, and pericarditis) after being started on clozapine, and whose symptoms remitted upon discontinuation of clozapine. The literature is reviewed and the treatment implications are discussed.     

Clinical implications of chromosomal abnormalities in 401 patients with myelodysplastic syndromes: a multicentric study in Japan

It is well known that cytogenetic analysis in patients with myelodysplastic syndrome (MDS) provides information useful in determining their prognosis. Based on the chromosomal results obtained from 401 MDS patients by a multicentric study in Japan, we studied correlations between chromosomal findings and prognosis or leukemic transformation in MDS patients. Patients with complex aberrations (cytogenetic abnormalities at more than three chromosomes), of any subtype, had a poor prognosis; for example, > 60% of patients with refractory anemia (RA) showing complex aberrations died within one year, but only 11% of them developed leukemia. In patients with RA with ringed sideroblasts (RARS), > 70% of those with complex aberrations evolved into the leukemic phase and survived for less than one year, suggesting a biologic heterogeneity in RARS patients. By contrast, about 5% of patients with RA or RARS exhibiting chromosomal findings other than -7/7q-, +8, two aberrations, and complex aberrations, developed leukemia and had a favorable prognosis. Therefore, the presence of chromosome abnormalities alone in patients with RA or RARS is not a factor in predicting leukemic transformation or poor prognosis. In patients with refractory anemia with an excess of blasts (RAEB), the presence of chromosome aberrations at MDS diagnosis affected the occurrence of leukemic transformation (24% versus 43%), however, no particular difference was noted in patients with RAEB in transformation with regard to whether they had chromosome changes or not, and about 60% of them evolved into leukemia. The poor prognosis related to complex aberrations was consistently noted in all MDS subtypes or age-matched groups, indicating that this cytogenetic anomaly is an independent risk factor for a poor prognosis in MDS patients. The duration between MDS diagnosis and development of the leukemic phase and that between the latter and death were significantly shorter in patients with complex aberrations than those without this change. Although the clinical significance of certain chromosomal abnormalities differs among subtypes of MDS, a new scoring system for predicting prognosis by cytogenetic changes, in combination with hematologic parameters, was proposed.     

Immunohistochemistry diagnosis of fungal infections

BACKGROUND: A potential beneficial outcome of treatment with certain of the atypical neuroleptics is the reduced risk of cognitive impairment, stemming from purported low affinity for cholinergic receptors. In vitro experiments have shown that clozapine is highly anticholinergic and risperidone is minimally so. In vivo tests of the anticholinergic burden imposed by these medications and its potential cognitive consequences are needed. This study examines anticholinergic burden in schizophrenia patients taking clozapine and risperidone and tests whether this burden is associated with cognitive deficits. METHOD: Serum anticholinergic levels were determined in a sample of 22 chronic schizophrenia patients using the radioreceptor assay method of Tune and Coyle (1980). Fifteen patients received clozapine; 7 received risperidone. Mean +/- SD age of the sample, comprising 12 men and 10 women (68% white), was 44.7 +/- 8.4 years. Mean +/- SD age at onset of schizophrenia illness was 23.5 +/- 7.4 years. Two anticholinergic assays based on blood samples collected 1 week apart were available on each patient. RESULTS: Data indicated that clozapine patients had significantly (p < .001) higher anticholinergic levels at both collection points, and levels for both drugs remained stable over time. The clozapine and risperidone patients had essentially equivalent scores on the cognitive measure. CONCLUSION: These data suggest that anticholinergicity distinguishes clozapine and risperidone in vivo but that this effect is not associated with differences in global cognitive functioning. Results suggest that clozapine, despite producing moderately high in vivo serum anticholinergic levels, still holds clinical advantage over standard neuroleptics in terms of cognitive side effects. Reasons for this lowered risk of cognitive impairment are discussed.     

Structural features associated with reactive metabolite formation in clozapine analogues

Clozapine is associated with a high incidence of agranulocytosis. We had previously found that it is oxidized by granulocytes, or simply HOCl, to a reactive metabolite that irreversibly binds to the cells, and we proposed that this reactive metabolite is responsible for clozapine-induced agranulocytosis. The reactive metabolite appeared to be a nitrenium ion formed by chlorination of the nitrogen bridge between the two aromatic rings. If this is correct, analogs that contain this structural feature should also be oxidized to a reactive intermediate while those not possessing this feature would, at least, not form the same type of reactive intermediate and, therefore, may not induce agranulocytosis. We tested the first part of this hypothesis with three clozapine analogs that do contain a nitrogen bridge and three that do not. Consistent with the hypothesis, the three analogs that do contain the nitrogen bridge formed reactive intermediates that could be trapped with glutathione when oxidized by HOCl, myeloperoxidase or activated neutrophils. In contrast, we found no evidence of a reactive intermediate on oxidation of analogs that contained an oxygen or sulfur bridge rather than a nitrogen bridge. If such reactive metabolites are responsible for drug-induced agranulocytosis, it should be possible to use such a simple screening method to test drugs at an early stage in their development for the potential to induce agranulocytosis.     

Clozapine occupies high levels of dopamine D2 receptors

An important discrepancy has been noted concerning the number of dopamine D2 receptors which must be occupied in patients by clozapine, in contrast to other antipsychotic drugs, in order to achieve an antipsychotic effect. For example, when D2 receptors are labelled by radioactive raclopride or spiperone congeners in patients, psychosis-controlling doses of all antipsychotic drugs occupy about 70% or more of the D2 receptors in patients. However, equi-effective psychosis-controlling doses of clozapine (approximately 400 mg/day; approximately 70-130 nM in spinal fluid) only occupy between 20% and 50% of the D2 receptors in patients. This discrepancy of a consistently lower occupancy of D2 by psychosis-controlling doses of clozapine may be resolved when one considers that the neuroleptic concentration for half-occupancy of D2 receptors in vitro (i.e. the inhibition constant) depends on the radioligand used to label the receptor. Radioligands with higher tissue/buffer partition coefficients are less displaced by clozapine. This principle applies both in vitro and in vivo. Thus, allowing for this principle, psychosis-controlling doses of clozapine can be shown to occupy over 70% of the brain dopamine D2 receptors in patients, as found with other neuroleptics.     

Early treatment decisions with interferon-alfa therapy in early chronic-phase chronic myelogenous leukemia

PURPOSE: To determine, in patients with Philadelphia chromosome (Ph)-positive chronic myelogenous leukemia (CML) on interferon alfa (IFNalpha), whether combining pretreatment characteristics and early response profiles would distinguish patients with differential benefits that would allow better decisions on subsequent therapy. PATIENTS AND METHODS: A total of 274 patients treated from 1982 through 1990 with IFNalpha regimens were analyzed. A second group of 137 patients treated with IFNalpha and low-dose cytarabine (ara-C) between 1990 and 1994 was later used to confirm the guidelines derived from the original study group analysis. Patients' pretreatment factors and response to IFNalpha therapy at 3, 6, and 12 months were analyzed in relation to subsequent achievement of major cytogenetic response. After univariate analysis of prognostic factors, a multivariate analysis selected, at 6 months, independent pretreatment factors that added to the response status in predicting subsequent outcome. The results were then applied at the 3- and 12-month periods and confirmed in the subsequent population. RESULTS: Response to IFNalpha therapy at 3, 6, and 12 months was a significant predictor of later major cytogenetic response. The presence of splenomegaly > or = 5 cm below the costal margin (BCM) or thrombocytosis > or = 700 x 10(9)/L pretreatment added significant independent prediction to response. At 6 months, patients with a partial hematologic response (PHR) or resistant disease had a less than 10% chance of achieving a later major cytogenetic response, as were those in complete hematologic response (CHR) and who had pretreatment splenomegaly and thrombocytosis. Applying the model at 3 months showed that only patients with < or = PHR and pretreatment splenomegaly or thrombocytosis at 3 months had such a low major cytogenetic response rate. Finally, at 12 months, patients with CHR still had a 15% to 25% chance of having a major cytogenetic response later if they did not have pretreatment splenomegaly and thrombocytosis. CONCLUSION: This analysis allows better selection of patients with Ph-positive CML on IFNalpha therapy for continuation of IFNalpha versus changing therapy early in the course of CML. For treatment programs that choose to change patients to other investigational therapies (eg, intensive chemotherapy and/or autologous stem-cell transplantation [SCT]), baseline outcome expectations are provided for patients continued on IFNalpha therapy, against which the results of new approaches can be compared.     

Busulfan-based regimens and allogeneic bone marrow transplantation in patients with myelodysplastic syndromes

Preparative regimens containing busulfan (BU) followed by allogeneic bone marrow transplantation (BMT) were used in 27 consecutive patients with myelodysplastic syndromes (MDS). The median age was 33 years (range, 4 to 54). Ten were female and 17 male. Sixteen patients had primary MDS, 11 other patients had antecedent hematologic diseases or developed MDS after cytotoxic and/or radiation therapy. Six patients had leukemic transformation and received antileukemic therapy before BMT. Pre-BMT cytogenetic studies showed complex chromosomal abnormalities in 13 patients, a simple abnormality in 5 patients, and normal chromosome in 8 patients. Three BU-based preparative regimens were used: 1 patient received BU 4 mg/kg orally (PO) daily for 4 days and cyclophosphamide (CY) 50 mg/kg intravenously (IV) daily for 4 days (BUCY-4); 24 patients received BU 4 mg/kg PO daily for 4 days, cytosine arabinoside (ara-C) 2 g/m2 IV every 12 hours for 4 doses, and CY 60 mg/kg IV daily for 2 days (BAC); and 2 patients with preceding Fanconi anemia received BU 2 mg/kg PO daily for 4 days followed by total lymphoid irradiation of 5 Gy. Seventeen of 27 patients are alive with no evidence of disease. Ten patients have died: 2 from hepatic veno-occlusive disease, 3 from sepsis, 1 from a cerebral bleed, 1 from a massive gastrointestinal (GI) bleed associated with acute graft-versus-host disease, 1 from hemolytic uremic syndrome with adult respiratory distress syndrome, 1 from bronchiolitis obliterans, and the only patient who did not engraft died from acute myeloid leukemia. Regimen-related toxicities (RRT) include GI tract (diarrhea, 14; stomatitis, 11), liver (9), cardiac (1), and skin (5). Patients who received a genotypically matched marrow graft had a significantly better disease-free survival (DFS) than patients who received a nongenotypic marrow graft (P = .02). The Kaplan-Meier analysis projects an overall DFS of 56% +/- 13% and 78% +/- 10% for patients who received a genotypically matched marrow graft. With the exception of a child who did not engraft, there was no relapse of MDS or leukemia. Excellent DFS, acceptable RRT, and the ease of administration are advantages of this regimen.     

Detection of minimal residual disease by polymerase chain reaction in patients with different hematologic diseases treated by bone marrow transplantation

Thirteen male patients affected by different hematologic diseases who underwent bone marrow transplantation (BMT) with female donors were investigated by cytogenetic analysis and polymerase chain reaction (PCR) amplification of a DNA sequence specific for the Y chromosome. In six of these patients, PCR showed the presence of the Y chromosome-related sequence; in only three of these did cytogenetic analysis confirm the presence of mixed chimerism. In the remaining three patients, the results of the PCR were confirmed by in situ hybridization on cell nuclei with a probe for the alpha-satellite of the Y chromosome. We compare results obtained with the two methods and discuss the meaning of the minimal residual disease detected by PCR in patients submitted to BMT.     

Chromosome studies in "preleukemia". III. Myelofibrosis

Cytogenetic studies were done on 18 patients with myelofibrosis or the closely related syndrome, undifferentiated myeloproliferative disorder (MPD). Clones of cells with chromosome abnormalities were demonstrated in the blood of eight individuals, including two with a history of radiation therapy and two with "acute myelofibrosis". Trisomy 8 was present in the latter two patients, but otherwise, there was no consistent cytogenetic pattern or correlation with specific hematologic findings. Sixteen of these patients have been followed for more than 1 year or until death; none has progressed to leukemia. The results indicate that chromosome abnormalities are relatively common in this disorder, but as with polycythemia vera, and unlike some other "preleukemic" states, the aberrant clones in myelofibrosis do not appear to indicate that clinical leukemia is imminent.     

Maternal cocaine alters eupneic ventilation but not gasping of neonatal rats

Lithium administration was used in a patient with a clozapine-induced neutropenia and in another with complete agranulocytosis to assess whether lithium could stimulate neutrophil production. In both cases, following lithium administration, the neutrophil count was increased to the normal range within 6 days. In the patient who had presented a neutropenia, clozapine treatment was then reinstated in the presence of lithium and continued without the neutrophil count dropping into the yellow-alert range thereafter.     

Effect of clozapine on motor function in schizophrenic patients

It is well established that clozapine is less likely than typical antipsychotic drugs to cause clinically discernible extrapyramidal side-effects. There is a paucity of data, however, on clozapine's motor effects. In this report we compare normal controls to groups of chronic schizophrenic patients treated with either typical antipsychotic drugs or with clozapine. Motor function was measured with a target-matching task, a test relying on submaximal sustained force control. Results indicated that patients on clozapine performed with significantly lower accuracy (greater variability) of force control. Even though the clozapine patients were treatment resistant to typical antipsychotic drugs, and many had a history of tardive dyskinesia, we postulate that the observed deficit is likely due to clozapine treatment rather than to earlier treatments or other factors. The observed force control deficit may be the result of an increase in myoclonus and a generally lower level of overall motor activity.     

GM-CSF can improve the cytogenetic response obtained with interferon-alpha therapy in patients with chronic myelogenous leukemia

Patients with chronic myelogenous leukemia (CML) who achieve a major cytogenetic remission when treated with interferon-alpha (IFN-A) have a survival advantage when compared to patients with no cytogenetic response. We investigated the effect of combining granulocyte-macrophage colony-stimulating factor (GM-CSF) with IFN-A in the cytogenetic response of patients with minor responses to IFN-A alone. CML patients were eligible if they had shown sensitivity to IFN-A as determined by achievement of a hematologic or cytogenetic response, but failed to achieve or lost a major cytogenetic response after a minimum of 12 months of therapy with IFN-A alone. Patients received GM-CSF 30 microg/m2 daily, subcutaneously and the dose was escalated to 60 microg/m2 if tolerated. IFN-A was continued at the same dose being received by the patient and escalated when possible. Fourteen evaluable patients were included, 13 in chronic phase and one in accelerated phase. The best response prior to GM-CSF was a transient major cytogenetic response in two patients (14%), minor cytogenetic response in nine (64%), and complete hematologic response in three (22%). The median time on IFN-A prior to the start of GM-CSF was 39 months (range 12-72 months). Four patients achieved a significant cytogenetic response, including two complete (14%) and two partial (14%) cytogenetic remissions during therapy. One partial cytogenetic remission converted to complete shortly after therapy was discontinued. Two other patients had a significant reduction in the percentage of Philadelphia chromosome-positive metaphases. The dose of IFN-A could be escalated in half of the patients treated. No toxicity could be attributed to the addition of GM-CSF. We conclude that the addition of GM-CSF to the treatment with IFN-A in CML patients who are sensitive to IFN-A alone but fail to achieve a major cytogenetic response may be beneficial in some patients and should be further investigated.     

Importance of sliding screw position in trochanteric fracture. 4 cases of secondary cervical fracture

Random chromosome abnormality is an important issue in clinical cytogenetics, especially in cancer cytogenetics. The significance of random abnormalities needs to be well defined. In the present study, ten patients with malignant hematologic disorders were analyzed by classical cytogenetic techniques and fluorescence in situ hybridization (FISH) procedures. Cytogenetic studies showed all ten patients to have a single cell with trisomy, i.e., +8, +8 (5 cases), +12, +15, +18, +20, and +21, respectively. FISH necessitated revision of the cytogenetic diagnosis and confirmed the clonality of these "random" abnormalities.     

Serotonin function and treatment response to clozapine in schizophrenic patients

OBJECTIVE: Clozapine is the only compound proven to be effective in the 20% of schizophrenic patients refractory to treatment with conventional neuroleptics. Although its mechanism of action has not been elucidated, clozapine appears, in contrast to most conventional neuroleptics, to be a potent serotonin (5-HT) antagonist. This study hypothesized that 5-HT function is increased in patients who benefit from clozapine treatment relative to patients who fail to improve on it. METHOD: The 5-HT receptor agonist m-chlorophenylpiperazine (MCPP) was used as a probe to examine 5-HT function. MCPP (0.35 mg/kg p.o.) was administered in a placebo-controlled design after a 3-week drug-free period to 19 schizophrenic patients. ACTH, prolactin, body temperature, behavior, and MCPP blood level were measured. Patients were then treated with a conventional neuroleptic, and, having failed to respond to it, were treated with clozapine for 5 weeks (up to 600 mg/day). RESULTS: Patients who responded to clozapine had significantly higher ACTH responses to MCPP during the drug-free state than the patients who failed to benefit from clozapine. Moreover, the degree of improvement with clozapine, particularly the improvement in psychotic symptoms, was strongly correlated with the magnitude of MCPP-induced ACTH release. Other MCPP-induced responses and MCPP blood level were similar for the two groups and did not correlate with the degree of symptomatic improvement with clozapine. CONCLUSIONS: Results of this study suggest that MCPP-induced ACTH release, and by inference 5-HT receptor function, may be increased in patients who benefit from treatment with clozapine relative to patients who fail to improve on this drug.     

Procainamide-induced agranulocytosis differs serologically and clinically from procainamide-induced lupus

Agranulocytosis is a well recognized but uncommon complication of procainamide (PA) therapy, whereas a lupus-like syndrome occurs in approximately 20% of patients treated chronically with PA. In order to gain insight into the immunopathogenic relationships among these conditions, we compared the humoral immune abnormalities in these patient groups as well as in asymptomatic PA-treated patients. A relatively uniform profile of IgM but not IgG autoantibody reactivity with a set of chromatin-related antigens was observed in eight elderly men who developed agranulocytosis after treatment with PA. In contrast PA-induced lupus patients had predominant reactivity with [(H2A-H2B)-DNA] in both IgM and IgG classes. Five of eight patients with agranulocytosis had elevated levels of neutrophil-reactive IgG which appeared to be due to immune complexes based on Fc gamma receptor blocking studies. However, 12 of 15 patients with PA-induced lupus, none of whom had neutropenia, had similar levels of neutrophil-reactive IgG, suggesting that this reactivity was not causally related to agranulocytosis. Agranulocytosis developed after less than 3 months treatment with PA in six of eight patients. This time course was similar to that seen in 77 PA-induced agranulocytosis patients reported in the literature plus 127 patients reported to the U.S. Food and Drug Administration in whom 90% developed agranulocytosis within 3 months of starting PA. In contrast, the mode duration of treatment with PA before lupus-like symptoms develop is 10-12 months. These findings, together with the different profiles of autoantibodies and clinical presentations, suggest that agranulocytosis arises from a different mechanism than that underlying PA-induced lupus.