Metabolic activation of chlorpromazine by stimulated human polymorphonuclear leukocytes. Induction of covalent binding of chlorpromazine to nucleic acids and proteins

Trends and off-label utilization of antipsychotics in children and adolescents from 2016 to 2021 in China: a real-world study

BACKGROUND

Global antipsychotic usage, including off-label prescriptions, has increased in recent decades. However, trends in China, particularly for children and adolescents, remain unclear. This study explored these trends from 2016 to 2021 and identified factors associated with off-label prescriptions.

METHODS

In this retrospective study, we analyzed on-label and off-label prescriptions based on drug information approved by the China National Medical Products Administration. To identify factors associated with off-label prescriptions, we conducted multivariate logistic regression analysis.

RESULTS

Our study included 48,258 antipsychotic prescriptions, 52.4% (25,295) of which were prescriptions for males. Of these, 61.7% (29,813) were off-label. Over time, the number of antipsychotics and the percentage of off-label prescriptions for children and adolescents overall increased from 2016 to 2021. The use of atypical antipsychotics increased, whereas that of typical antipsychotics decreased. For off-label usage, all of the factors in our study were associated with off-label usage, including age, sex, year, region, department, reimbursement, antipsychotic type, drug expense, number of polypharmacy and diagnoses. Additionally, tiapride (15.8%) and aripiprazole (18.6%) were the most common typical and atypical antipsychotics, respectively. For pediatric diseases, common diagnoses included mood or affective disorders (31.7%) and behavioral and emotional disorders, with onset usually occurring in childhood and adolescence (29.1%). Furthermore, a depressive state was the most common diagnosis for which antipsychotic polypharmacy was used for treatment.

CONCLUSION

In this retrospective study, off-label antipsychotic prescriptions were common, with trends generally increasing among children and adolescents from 2016 to 2021. However, there is a lack of evidence supporting off-label usage, thus emphasizing the need for studies on the efficacy and safety of these treatments.

Peroxidase catalysed formation of cytotoxic prooxidant phenothiazine free radicals at physiological pH

The antipsychotic phenothiazines may have other therapeutic applications because of their ability to kill bacteria, plasmids and tumor cells. They are also known to undergo a peroxidase-catalysed oxidation to form cation radicals that are stable at acid pH, but are not detected at a neutral pH. The objective of this project was to determine whether phenothiazine cation radical metabolites could cause oxidative stress at a neutral pH resulting in cytotoxicity. At a neutral pH, catalytic amounts of phenothiazines were found to be oxidised by a peroxidase/H2O2 system and also caused ascorbate, GSH and NADH cooxidation. NADH and GSH co-oxidation was accompanied by oxygen uptake and was increased by the addition of catalytic amounts of superoxide dismutase, indicating that the superoxide radical was formed. The phenothazines were different from other peroxidase substrates in that the NADH, ascorbate or GSH cooxidation was faster at pH 6.0 than pH 7.4, thereby partly reflecting the cation radical stability. The order of catalytic effectiveness found was promazine > chlorpromazine > trifluoperazine. Peroxidase/H2O2 also markedly increased phenothiazine cytotoxicity towards isolated rat hepatocytes at nontoxic phenothiazine concentrations. At both pH 6.0 and 7.4, the same order of phenothiazine catalytic effectiveness was observed as seen in the co-oxidation experiments. Cytotoxicity to hepatocytes could be attributed to oxidative stress as most hepatocyte glutathione oxidation and lipid peroxidation preceded phenothiazine induced cytotoxicity and that cytotoxicity was prevented by the antioxidant butylated hydroxyanisole. This hepatocyte/peroxidase/H2O2 system could be a useful model for studying drug induced idiosyncratic hepatic injury enhanced by inflammation.

Phenothiazines: potential alternatives for the management of antibiotic resistant infections of tuberculosis and malaria in developing countries

The in vitro and in vivo activity of phenothiazines against antibiotic susceptible and antibiotic resistant Mycobacterium tuberculosis and malaria-causing Plasmodia is reviewed. Given the facts that pulmonary tuberculosis and malaria are the major causes of death in developing countries, that both of these infections continue to escalate in their resistance to antibiotics, that the cost for the management of these infections is beyond that afforded by most developing nations, and lastly, that new and effective agents are not forthcoming from the pharmaceutical industry, the scientific rationale for the potential use of select phenothiazines for the management of these infections is presented.

Trypanosoma cruzi trypanothione reductase is inactivated by peroxidase-generated phenothiazine cationic radicals

Trypanosoma cruzi trypanothione reductase (TR) was irreversibly inhibited by peroxidase/H2O2 /phenothiazine (PTZ) systems. TR inactivation depended on (a) time of incubation with the phenothiazine system; (b) the peroxidase nature and (c) the PTZ structure and concentration. With the most effective systems, TR inactivation kinetics were biphasic, with a relatively fast initial phase during which about 75% of the enzyme activity was lost, followed by a slower phase leading to total enzyme inactivation. GSH prevented TR inactivation by the peroxidase/H2O2/PTZ+* systems. Production of PTZ+* cation radicals by PTZ peroxidation was essential for TR inactivation. Horseradish peroxidase, leukocyte myeloperoxidase (MPO) and the pseudo-peroxidase myoglobin (Mb) were effective catalysts of PTZ+* production. Promazine, thioridazine, chlorpromazine, propionylpromazine prochlorperazine, perphenazine and trimeprazine were effective constituents of the HRP/H2O2 /PTZ system. The presence of substituents at the PTZ nucleus position 2 exerted significant influence on PTZ activity, as shown by the different effects of 2-trifluoromethyl and 2-H or 2-chlorophenothiazines. The PTZ+* cation radicals disproportionation regenerated the non-radical PTZ molecule and produced the PTZ sulfoxide that was inactive on TR. Thiol compounds including GSH interacted with PTZ+* cation radicals transferring an electron from the sulfide anion to the PTZ+*, thus nullifying the PTZ+* biological and chemical activities.

Phagocyte-mediated oxidation in idiosyncratic adverse drug reactions

The drug-metabolizing capacity of the liver is well known but cannot account for most idiosyncratic adverse drug reactions. Of the extrahepatic sources of reactive drug metabolites, the neutrophil has received the most attention because of its vast numbers and robust oxidizing machinery. Many drugs associated with autoimmunity are susceptible to oxidative transformation by the enzymatic action of myeloperoxidase, a protein released into the extracellular environment when neutrophils are activated. Production of the resulting drug metabolites within lymphoid organs maximizes their immune-perturbing effects. Mechanisms proposed for the initiation of drug-induced blood dyscrasias, hypersensitivity reactions, or lupus-like symptoms center around three views: (1) presentation of the implicated compound in the major histocompatibility complex of antigen-presenting cells via direct binding or after processing as a hapten bound to self-macromolecules, (2) direct cytotoxicity, or (3) interference in the development of T-cell tolerance in the thymus. How participation of reactive drug metabolites in these processes might lead to symptomatic disease is discussed.

Human term placental lipoxygenase-mediated N-demethylation of phenothiazines and insecticides in the presence of linoleic acid

This study investigated the hypothesis that human term placental lipoxygenase (HTPLO) and soybean lipoxygenase (SLO) are capable of mediating N-demethylation of selected phenothiazines and insecticides in the presence of linoleic acid (LA). In addition to being LA dependent, the N-demethylation reaction mediated by HTPLO and SLO was limited by incubation time, pH of the medium, concentration of the enzyme and the substrate. Using Nash reagent to monitor formaldehyde production, the specific activity for LA-dependent N-demethylation of chlorpromazine, a model phenothiazine, was determined to be 1.7+/-0.3 nmoles/min/mg HTPLO. Besides chlorpromazine, N-demethylation of promazine, promethazine and trimeprazine was also observed. The insecticide, aminocarb, displayed a specific activity of 2.2+/-0.3 nmoles/min/mg HTPLO for N-demethylation. Other insecticides, namely chlordimeform, dicrotophos and zectran, were oxidized in a similar manner. As compared with HTPLO, the rates of N-demethylation of phenothiazines and insecticides mediated by SLO were higher. Classical inhibitors of lipoxygenase, as well as antioxidants and free radical scavengers, caused a dose-dependent reduction in the production of formaldehyde from chlorpromazine and aminocarb by HTPLO. These results clearly demonstrate the ability of polyunsaturated free fatty acids to support N-demethylation of xenobiotics via the lipoxygenase pathway.

Etiology and mechanisms of drug-induced lupus

Systemic rheumatic symptoms occur with widely different frequencies as a side effect of long-term therapy with some 39 medications currently in use. Because symptoms are nonspecific, subjective, and protean, diagnosis of drug-induced lupus (DIL) requires awareness of this risk of chronic medication. However, laboratory features and the characteristic of full recovery after discontinuing treatment are helpful in differentiating drug-induced from spontaneous lupus or other syndromes. Drug-induced lupus is probably mediated by reactive drug metabolites, not the ingested medications, and susceptibility to neutrophil-mediated oxidative transformation is a property of ten lupus-inducing drugs reported so far. Mechanisms for DIL modeled after drug hypersensitivity reactions are unsupported experimentally and inconsistent with the features of DIL. However, several new lines of investigation using mouse models have opened up promising leads into the origin of autoreactive T cells and disease development in DIL.

Effect of some psychotropic drugs on the activated macrophage-induced luminol-dependent chemiluminescence

The effect of some psychotropic drugs on the activity of macrophages to produce superoxide radicals during phagocytosis was tested. Three-cyclic antidepressants, imipramine and amitriptyline, and the thioxanthene neuroleptic, chlorprothixene, were studied. The superoxide production was measured by luminol-dependent chemiluminescence. The drugs were investigated in the concentration range of 10(-7)-10(-4) mol/l. It was seen that all tested drugs caused a concentration-dependent decrease of the luminol-dependent chemiluminescence. The inhibitory effect of imipramine and amitriptyline on the macrophage superoxide production was moderate, while the effect of chlorprothixene was significantly stronger (a decrease more than 100 times that of macrophage chemiluminescence). Essentially, the luminol-dependent chemiluminescence reflects the level of superoxide radicals in the system. Therefore, the effect of drugs may be due to the possible activity for scavenging superoxide. In additional experiments with different systems of generations of O2- and different methods of registration, this possibility was discarded. Therefore, the effect of the drugs on the luminol-dependent chemiluminescence seems to be due to drug-induced decrease of the ability of activated macrophages to produce superoxide radicals.

Comparative oxidation of loxapine and clozapine by human neutrophils

The clozapine-induced agranulocytosis could be due to the formation of a reactive intermediate formed in polymorphonuclear neutrophils and granulocyte precursors with the myeloperoxidase-hydrogen peroxide system. On the contrary, no case of agranulocytosis has been described for loxapine, an other neuroleptic drug with a very close structural analogy. We have compared the clozapine and loxapine interaction with the oxidative burst and particularly with this enzymatic complex. On the one hand, the assay of the oxidative species demonstrated a different impact for the two neuroleptics. The 50% inhibitory concentration was 92 microM for hydrogen peroxide and 40 microM for hypochlorous acid for loxapine. The loxapine target is located before the myeloperoxidase-hydrogen peroxide system in the oxidative stream, whereas clozapine diverts the chlorination pathway of the enzyme. On the other hand, the in vitro metabolism of drugs by the myeloperoxidase-hydrogen peroxide system has been investigated by mass spectrometry. Loxapine remains inert but clozapine undergoes the oxidation. The glutathione or ascorbate addition in the medium leads to a removal of the oxidation. Glutathione is able to trap the toxic intermediate and could avoid its formation.

Transformation of lupus-inducing drugs to cytotoxic products by activated neutrophils

Drug-induced lupus is a serious side effect of certain medications, but the chemical features that confer this property and the underlying pathogenesis are puzzling. Prototypes of all six therapeutic classes of lupus-inducing drugs were highly cytotoxic only in the presence of activated neutrophils. Removal of extracellular hydrogen peroxide before, but not after, exposure of the drug to activated neutrophils prevented cytotoxicity. Neutrophil-dependent cytotoxicity required the enzymatic action of myeloperoxidase, resulting in the chemical transformation of the drug to a reactive product. The capacity of drugs to serve as myeloperoxidase substrates in vitro was associated with the ability to induce lupus in vivo.

Enzymatic oxidation of phenothiazines by lipoxygenase/H2O2 system

Lipoxygenase (LOX) (EC 1.13.11.12) oxidized a wide range of phenothiazine (Pt) tranquillizers to their corresponding radical cations in the presence of H2O2 by means of an enzymatic chemical second-order mechanism with substrate regeneration similar to that of horseradish peroxidase. The optimum pH of LOX for this hydroperoxidase activity was in the acid range (pH 3.0-4.0), as has been shown for other Pt oxidizing systems, such as peroxidase/H2O2 and haemoglobin. LOX showed Michaelis constants for Pt ranging from 1.4 to 8.5 mM and which, in some cases, e.g. trifluoperazine, displayed substrate inhibition. By contrast, it had a high affinity for H2O2 in the microM to mM range. A new, previously undescribed plot, which relates the enzymatic affinity and the apparent second-order decay of the cation radical, was developed to study the influence of the 2- and 10-substituents in the Pt ring. The implications of this new plot and the LOX-mediated Pt oxidation are also discussed.

Possible role of HLA in hepatotoxicity. An exploratory study in 71 patients with drug-induced idiosyncratic hepatitis

Possible associations between particular human leucocyte antigen molecules and immunoallergic hepatitis have been suggested previously (HLA-A11 in halothane hepatitis, HLA-DR6 and DR2 in nitrofurantoin hepatitis, HLA-B8 in clometacin hepatitis). In this study the HLA haplotype was determined in 71 patients with idiosyncratic hepatitis due to different drugs. The prevalence of HLA-A11 was twice as high in the 71 patients in the study (23%) as in controls (12%), but p-values were not significant when corrections were made for the large number of comparisons (n = 39). The prevalences of HLA-DR2, DR6, and B8 were similar in the 71 patients and in controls. When hepatitis due to particular drugs was considered, HLA-A11 was found to be present in six of 12 patients (50%) with hepatitis caused by tricyclic antidepressants, and three of four patients (75%) with diclofenac hepatitis, compared to 12% in controls. HLA-DR6 was present in four of five patients (80%) with chlorpromazine hepatitis, compared to 22% in controls. In conclusion, the HLA phenotype does not contribute significantly to idiosyncratic drug-induced hepatitis considered collectively. Possible associations between some HLA molecules and the hepatotoxicity of certain drugs require further confirmation.