Thymoleptic and neuroleptic drug plasma levels in psychiatry: current status

Multifaceted effect of chlorpromazine in cancer: implications for cancer treatment

Since its discovery in 1951, chlorpromazine (CPZ) has been one of the most widely used antipsychotic medications for treating schizophrenia and other psychiatric disorders. In addition to its antipsychotic effect, many studies in the last several decades have found that CPZ has a potent antitumorigenic effect. These studies have shown that CPZ affects a number of molecular oncogenic targets through multiple pathways, including the regulation of cell cycle, cancer growth and metastasis, chemo-resistance and stemness of cancer cells. Here we review studies on molecular mechanisms of CPZ’s action on key proteins involved in cancer, including p53, YAP, Ras protein, ion channels, and MAPKs. We discuss common and overlapping signaling pathways of CPZ’s action, its cancer-type specificity, antitumorigenic effects of CPZ reported in animal models and population studies on the rate of cancer in psychiatric patients. We also discuss the potential benefits and limitations of repurposing CPZ for cancer treatment.

Monitoring of tricyclic antidepressant plasma levels and clinical response: a review of the literature. Part II

Part II of this paper contains some general considerations on tricyclic antidepressant (TCA) monitoring. Long-term assessment of TCA plasma levels is advised by the few existent studies, although each of these focusses on different aspects. Cardiovascular and central nervous system toxicity is reviewed as well as pharmacokinetics and the importance of protein binding. Some consideration is also given to their use in elderly patients. The authors conclude that although available data support its usefulness in many situations, routine measurement of TCA levels is not warranted.

Influence of antibiotics and food intake on liver glutathione and cytochrome P-450 in septic rats

Experimental sepsis in rats induces a restriction in spontaneous food intake and a drop in liver glutathione, cytochrome P-450 (P-450) and aminopyrine demethylase (AD) activity. The present study was designed to assess the effects of antibiotics alone or when combined with food deprivation on these variables. Eighty-nine male Sprague-Dawley rats were assigned to six groups: control (C), acute infection (experimental pyelonephritis, I), acute infection with antibiotics and food givenad lib. (IA), control with antibiotics (CA), acute infection with antibiotics pair-fed to I (IAR), and sham-operated pair-fed to I (SR). Liver glutathione, P-450 and AD activities were reduced by 45·2, 79·8 and 41·2% respectively in group I. Glutathione and AD significantly increased only in those infected rats given antibiotics and allowed free access to food. P-450 did not normalize within the study period in infected rats receiving antibiotics and food repletion. The risk of drug hepatotoxicity in acute septic states is therefore closely related to the nutritional status. From this point of view, nutritional support is almost as important as treatment of infection.

Block of HERG Human K+ Channel and IKr of Guinea Pig Cardiomyocytes by Chlorpromazine

Chlorpromazine, a commonly used antipsychotic drug, has been known to induce QT prolongation and torsades de pointes, which can cause sudden death. We studied the effects of chlorpromazine on the human ether-a-go-go-related gene (HERG) channel expressed in Xenopus oocytes and on delayed rectifier K current of guinea pig ventricular myocytes. Application of chlorpromazine showed a dose-dependent decrease in the amplitudes of steady-state currents and tail currents of HERG. The decrease became more pronounced at increasingly positive potential, suggesting that the blockade of HERG by chlorpromazine is voltage dependent. IC50 for chlorpromazine block of HERG current was progressively decreased according to depolarization: IC50 values at -30, 0, and +30 mV were 10.5, 8.8, and 4.9 microM, respectively. The block of HERG current during the voltage step increased with time starting from a level 89% of the control current. In guinea pig ventricular myocytes, bath application of 2 and 5 microM chlorpromazine at 36 degree C blocked rapidly activating delayed rectifier K current (IKr) by 31 and 83%, respectively. How-ever, the same concentrations of chlorpromazine failed to significantly block slowly activating delayed rectifier K current (IKs). Our findings suggest that the arrhythmogenic side effect of chlorpromazine is caused by blockade of HERG and rapid component of delayed rectifier K current rather than by blockade of the slow component.

Bioelectric toxicity caused by chlorpromazine in human lung epithelial cells

Endogeneous and exogeneous amine-containing substances possess pneumophilic properties. Among them, tricyclic amphiphilic amine drugs like neuroleptics intensively accumulate in the lung cell membrane and occasionally cause severe respiratory disorders. In the present study, we examined the bioelectric toxicity of chlorpromazine (CPZ), a commonly used neuroleptic, in human lung epithelial cells. CPZ concentration-dependently inhibited the isoproterenol (ISO)-generated short-circuit current (I(sc)) sensitive to a nonselective K(+) channel blocker, clotrimazole (30 microM), but insensitive to a selective Ca(2+)-activated K(+) (K(Ca)) channel blocker, charybdotoxin (ChTx, 100 nM). The effects of apical CPZ on the ISO-induced responses were greater than those of basolateral CPZ. Forskolin- and 8-bromo-cyclic AMP-induced I(sc) were partially prevented by CPZ. Nystatin permeabilization of the monolayers revealed that CPZ attenuated the basolateral K(+) current elicited by ISO more than that elicited by forskolin and that the apical Cl(-) current elicited by forskolin was instead potentiated by CPZ, although it inhibited the ISO-induced Cl(-) current. 1-Ethyl-2-benzimdazolinone (1-EBIO, a K(Ca) channel opener, 500 microM)- and ionomycin (Ca(2+) ionophore, 1 microM)-evoked Cl(-) secretions were also sensitive to CPZ. These results indicate that CPZ inhibits transepithelial Cl(-) transport, affecting at least two different targets: the beta-adrenergic receptor and the basolateral K(+) channels (especially the K(Ca) channel). Electrostatic interactions at the inner surface of the membrane between the protonated amines of CPZ and negatively charged portions of the plasma membrane may be involved in the mechanisms.

Torsades de pointes associated with chlorpromazine: case report and review of associated ventricular arrhythmias

PURPOSE

To present a case of chlorpromazine-associated torsades de pointes, review established cases of ventricular arrhythmias associated with chlorpromazine, and describe the proarrhythmic characteristics of this drug.

DATA SOURCES

Articles identified through a search of MEDLINE and IDIS from January 1966-November 2000 and thorough review of the article bibliographies. Patient cases also were identified from a search of the Food and Drug Administration's Adverse Event Reporting System database (November 1997-March 2001). Cases involving intentional overdoses of chlorpromazine were excluded.

RESULTS

In addition to the case reported herein, 12 cases of documented, chlorpromazine-associated ventricular arrhythmias were identified; five had characteristic features of torsades de pointes. Chlorpromazine delayed repolarization and produced electrocardiographic abnormalities; although, whether chlorpromazine induced torsades de pointes through a mechanism of early afterdepolarizations is unclear. Similar to other instances of drug-induced torsades de pointes, concurrent factors such as electrolyte deficiencies may place the patient at increased risk for arrhythmia.

CONCLUSIONS

Chlorpromazine can delay repolarization and produce electrocardiographic abnormalities. These can result infrequently in ventricular arrhythmias and torsades de pointes, particularly in patients with confounding factors.

Blockade by trifluoperazine of a Ca(2+)-activated K+ channel in rat hippocampal pyramidal neurons

The effects of trifluoperazine, a phenothiazine derivative, on the large-conductance Ca(2+)-activated K+ channel (BKCa) in dissociated rat hippocampal pyramidal neurons were examined using the inside-out configuration of the patch-clamp technique. The BKCa was activated by 12.6 microM Ca2+ on the internal surface of the membrane patch. The single channel conductance of the BKCa was 244 +/- 17.5 pS (n = 10) in symmetrical solutions of 150 mM K+. Trifluoperazine, applied on the internal surface of the membrane, decreased the open probability of the channel without changing the single channel conductance. The reduction in the open probability was well described by a block of the open state of the channel in a simple sequential model. The apparent dissociation constant (KD) for the reduction was calculated to be 1.4 microM and the Hill coefficient 0.69 at +20 mV. The inhibition was voltage dependent, being more pronounced at depolarized voltages. The voltage dependence enabled us to estimate that the binding site for the agent in the channel lies about half way across the membrane electrical field. It is concluded that trifluoperazine blocks the open state of the BKCa, which is known to provide an outward current for repolarization and afterhyperpolarization of the neuronal action potential. This may result in a decrease in spike intervals during burst firing of neurons.

Differential block of sodium and calcium channels by chlorpromazine in mouse neuroblastoma cells

1. The effects of chlorpromazine on the voltage-activated sodium and type I (transient) calcium channels were studied in cultured mouse neuroblastoma cells (N1E-115) using the whole-cell patch-clamp technique. 2. Chlorpromazine (2-10 x 10(-6) M) blocked both the sodium channel current and the calcium channel current as carried by Ba2+ in a reversible and dose-dependent manner. 3. The block was not associated with any change in the time course of the activation and inactivation of the sodium and calcium channel currents. 4. The dose-response relationships for the block of these channels measured with a holding potential of -120 mV indicated a 1:1 binding stoichiometry with apparent dissociation constants of 2.5 +/- 10(-6) M and 1.5 +/- 10(-5) M for the sodium and calcium channels, respectively. 5. The block was dependent on the holding potential for both channel currents. The apparent dissociation constant for the sodium channel was decreased to 0.65 +/- 10(-6) M when the membrane was held at -80 mV. The apparent dissociation constant for the calcium channel was decreased to 3.2 +/- 10(-6) M when the membrane was held at -60 mV. 6. The steady-state inactivation curve for the sodium channel was shifted by 12.4 +/- 1.8 mV to more negative potentials by exposure to 1 x 10(-6) M-chlorpromazine. The inactivation curve for the calcium channel was also shifted by 15.4 +/- 3.2 mV to more negative potentials by exposure to 1 x 10(-5) M-chlorpromazine. These results indicate a greater affinity of chlorpromazine for the inactivated state of the channels than for the resting state. 7. Chlorpromazine caused a marked use-dependent block of the sodium channel current, as demonstrated by a cumulative increase of the block during a train of depolarizing pulses. The use-dependent block was observed even with an interpulse interval as long as 2 s. 8. On the other hand, the block of the calcium channel current did not notably accumulate during a train of depolarizing pulses even when extremely prolonged (1 s) pulses were applied at a very short interpulse interval (200 ms). 9. The marked use dependence of the sodium channel block was due to a very slow repriming of the drug-bound sodium channels from inactivation, whereas the lack of use dependence of the calcium channel block was due to a rapid repriming of the drug-bound calcium channels.(ABSTRACT TRUNCATED AT 400 WORDS)

Modulation of sodium current kinetics by chlorpromazine in freshly-isolated striatal neurones of the adult guinea-pig

1. The neurones of the striatum were freshly dissociated from the adult guinea-pig brain by enzymatic and mechanical treatments. Sodium channel current kinetics in these neurones were measured using a whole cell variation of the patch-clamp technique. 2. Chlorpromazine, a neuroleptic, in micromolar concentrations reversibly reduced the amplitude of the sodium currents. Activation and inactivation time constants were not affected. The inhibition followed one-to-one binding stoichiometry. 3. The concentration-response curve shifted to the left when the holding potential was less negative. The EC50 shifted from 4.8 microM to 0.9 microM when the holding potential was changed from -120 mV to -70 mV. 4. The steady-state activation curve of the sodium current was not affected by chlorpromazine, whereas the steady-state inactivation curve was shifted in the negative direction. Consequently, the window current which is normally present at a potential range around -50 mV was decreased in the presence of chlorpromazine. 5. Successive sodium currents evoked by a train of depolarizing pulses (30 ms duration) to -10 mV showed a cumulative decrease in size during the application of chlorpromazine. However, such 'use-dependent' block was not observed when the pulse duration was reduced to 1 ms. 6. The recovery from inactivation in the presence of chlorpromazine, was expressed as a second order process. The faster component was similar to the recovery time course of the normal sodium channels. The slower component accounted for the use-dependent effect of chlorpromazine. 7. The results indicate that chlorpromazine binds to the resting sodium channels producing steady-state block at a very negative holding potential. When the membrane is depolarized, chlorpromazine binds to the inactivated form of the sodium channels with much higher affinity and stabilizes them in the inactivated state, slowing their kinetics.

Psychotropic drugs block voltage-gated ion channels in neuroblastoma cells

Effects of neuroleptics and tricyclic antidepressants on voltage-gated ion channels were investigated in the neuroblastoma cell line N1E-115 using the whole cell variation of patch electrode voltage-clamp techniques. Imipramine, chlorpromazine and haloperidol in micromolar concentrations blocked sodium, calcium and potassium channel currents in a reversible and concentration-dependent manner. The order of potency was chlorpromazine greater than imipramine greater than haloperidol. These direct blocking actions on neuronal ion channels might play a role in clinical effects of these drugs.

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.

Neuroleptic blood levels and therapeutic effect

Studies attempting to delineate a therapeutic range of blood levels for neuroleptics have yielded conflicting results. The reasons for this are briefly reviewed and a study is described in which a correlation is sought between blood levels of thioridazine and clinical efficacy. The study employs the radioreceptor assay for neuroleptics to detect both parent drug and active metabolites in blood. The results of the study indicate that while dose is a poor predictor of blood levels of medication, blood levels of neuroleptic activity in patients on thioridazine may be very highly correlated with antipsychotic effect.

Specific radioimmunoassay of amitriptyline and nortriptyline

1 Antisera to nortriptyline were prepared by immunizing rabbits with N-succinylnortriptyline--bovine serum albumin conjugate. 2 A sensitive radioimmunoassay has been developed for the tricyclic antidepressants amitriptyline and nortriptyline. 3 amitriptyline and nortriptyline are separated from each other and from interfering metabolites before assay. 4 Using [3H]-imipramine and [3H]-succinylnortriptyline as tracers the radioimmunoassay can measure amitriptyline and nortriptyline levels down to 2--3 ng/ml using 0.05 ml plasma sample. 5 Agreement between the radioimmunoassay and a gas-chromatographic assay was excellent for both amitriptyline and nortriptyline.

Radioimmunoassay of amitriptyline and nortriptyline in body fluids

A radioimmunoassay for the measurement of amitriptyline and nortriptyline in serum, saliva, and urine is described. The sensitivity of the assay is such that 0.5 ng/ml of drug can be measured, although the assay does not distinguish between amitriptyline and nortriptyline. Other tricyclic compounds cross-react with the antiserum to varying degrees, but the metabolites of amitriptyline did not significantly cross-react. Total tricyclic compounds were detected in serum and saliva after single oral doses of amitriptyline, although the absorption was slow.