Risk Assessment of Psychotropic Drugs on Mitochondrial Function Using In Vitro Assays

Mitochondria are potential targets responsible for some drug- and xenobiotic-induced organ toxicities. However, molecular mechanisms of drug-induced mitochondrial toxicities are mostly unknown. Here, multiple in vitro assays were used to investigate the effects of 22 psychotropic drugs on mitochondrial function. The acute extracellular flux assay identified inhibitors of the electron transport chain (ETC), i.e., aripiprazole, phenytoin, and fluoxetine, an uncoupler (reserpine), substrate inhibitors (quetiapine, carbamazepine, buspirone, and tianeptine), and cytotoxic compounds (chlorpromazine and valproic acid) in HepG2 cells. Using permeabilized HepG2 cells revealed minimum effective concentrations of 66.3, 6730, 44.5, and 72.1 µM for the inhibition of complex-I-linked respiration for quetiapine, valproic acid, buspirone, and fluoxetine, respectively. Assessing complex-II-linked respiration in isolated rat liver mitochondria revealed haloperidol is an ETC inhibitor, chlorpromazine is an uncoupler in basal respiration and an ETC inhibitor under uncoupled respiration (IC50 = 135 µM), while olanzapine causes a mild dissipation of the membrane potential at 50 µM. This research elucidates some mechanisms of drug toxicity and provides some insight into their safety profile for clinical drug decisions.

Pharmacokinetic and pharmacodynamic of the cognitive enhancer modafinil: Relevant clinical and forensic aspects

Modafinil is a nonamphetamine nootropic drug with an increasingly therapeutic interest due to its different sites of action and behavioral effects in comparison to cocaine or amphetamine. A review of modafinil (and of its prodrug adrafinil and its R-enantiomer armodafinil) chemical, pharmacokinetic, pharmacodynamic, toxicological, clinical and forensic aspects was performed, aiming to better understand possible health problems associated to its unconscious and unruled use. Modafinil is a racemate metabolized mainly in the liver into its inactive acid and sulfone metabolites, which undergo primarily renal excretion. Although not fully clarified, major effects seem to be associated to inhibition of dopamine reuptake and modulation of several other neurochemical pathways, namely noradrenergic, serotoninergic, orexinergic, histaminergic, glutamatergic and GABAergic. Due its wake-promoting effects, modafinil is used for the treatment of daily sleepiness associated to narcolepsy, obstructive sleep apnea and shift work sleep disorder. Its psychotropic and cognitive effects are also attractive in several other pathologies and conditions that affect sleep structure, induce fatigue and lethargy, and impair cognitive abilities. Additionally, in health subjects, including students, modafinil is being used off-label to overcome sleepiness, increase concentration and improve cognitive potential. The most common adverse effects associated to modafinil intake are headache, insomnia, anxiety, diarrhea, dry mouth and raise in blood pressure and heart rate. Infrequently, severe dermatologic effects in children, including maculopapular and morbilliform rash, erythema multiforme and Stevens-Johnson Syndrome have been reported. Intoxication and dependence associated to modafinil are uncommon. Further research on effects and health implications of modafinil and its analogs is steel needed to create evidence-based policies.

Enantiospecific effects of chiral drugs on cytochrome P450 inhibition in vitro

1. The aim of this work was to examine the differences in the inhibitory potency of individual enantiomers and racemic mixtures of selected chiral drugs on human liver microsomal cytochromes P450. 2. The interaction of enantiomeric forms of six drugs (tamsulosin, tolterodine, citalopram, modafinil, zopiclone, ketoconazole) with nine cytochromes P450 (CYP3A4, CYP2E1, CYP2D6, CYP2C19, CYP2C9, CYP2C8, CYP2B6, CYP2A6, CYP1A2) was examined. HPLC methods were used to estimate the extent of the inhibition of specific activity in vitro. 3. Tamsulosin (TAM) and tolterodine (TOL) inhibited CYP3A4 activity with an enantiospecific pattern. The inhibition of CYP3A4 activity differed for R-TAM (Ki 2.88 ± 0.12 µM) and S-TAM (Ki 14.22 ± 0.53 µM) as well as for S-TOL (Ki 1.71 ± 0.03 µM) and R-TOL (Ki 4.78 ± 0.17 µM). Also, the inhibition of CYP2C19 by ketoconazole (KET) cis-enantiomers exhibited enantioselective behavior: the (+)-KET (IC50 23.64 ± 6.25 µM) was more potent than (-)-KET (IC50 66.12 ± 12.6 µM). The inhibition of CYP2C19 by modafinil (MOD) enantiomers (R-MOD IC50 = 51.79 ± 8.58 µM, S-MOD IC50 = 48.62 ± 9.74 µM) and the inhibition of CYP2D6 by citalopram (CIT) enantiomers (R-CIT IC50 = 68.17 ± 5.70 µM, S-CIT IC50 = 62.63 ± 7.89 µM) was not enantiospecific. 4. Although enantiospecific interactions were found (TAM, TOL, KET), they are probably not clinically relevant as the plasma levels are generally lower than the drug concentration needed for prominent inhibition (at least 50% of CYP activity).

Evaluation of the potential for a pharmacokinetic drug-drug interaction between armodafinil and ziprasidone in healthy adults

BACKGROUND

Armodafinil has been studied as adjunctive therapy for major depressive episodes associated with bipolar I disorder. This open-label, single-centre, 2-period study evaluated the effect of armodafinil, a moderate inducer of cytochrome-P450 (CYP) isoenzyme CYP3A4, on the pharmacokinetics and safety of ziprasidone, an atypical antipsychotic used to treat bipolar I disorder and metabolized in part by CYP3A4.

METHODS

Thirty-five healthy subjects received ziprasidone (20 mg) alone and after armodafinil pretreatment (titrated to 250 mg/day); of those, 25 were evaluable for pharmacokinetics. Pharmacokinetic parameters were derived from plasma concentrations of ziprasidone collected prior to and over the 48 h after each ziprasidone administration. Plasma concentrations of armodafinil and its circulating metabolites, R-modafinil acid and modafinil sulfone, were also obtained after repeated daily dosing of armodafinil alone. Safety and tolerability were assessed.

RESULTS

Systemic exposure to ziprasidone was similar following administration alone or after pretreatment with armodafinil, as assessed by mean peak plasma concentration (C max, 52.1 vs 50.4 ng/mL) and area under the plasma concentration-time curve from time 0 to infinity (AUC0-∞, 544.6 vs 469.1 ng·h/mL). Geometric mean ratios of systemic exposure (ziprasidone alone: ziprasidone after pretreatment with armodafinil) were close to unity, with associated 90 % confidence intervals (CIs) within the range of 0.80-1.25 (C max, 0.97; 90 % CI, 0.87-1.08; AUC0-∞, 0.86; 90 % CI, 0.82-0.91). Adverse events were consistent with the known safety profiles of each agent.

CONCLUSION

Systemic exposure to ziprasidone was not affected by pretreatment with armodafinil. Both drugs were generally safe and well tolerated under the conditions studied.

A framework to avoid irrational polypharmacy in psychiatry

Many patients with psychiatric disorders do not obtain remission from available pharmacological and psychotherapeutic treatments. Recent studies have demonstrated that there is a role for the rational use of 'combination therapy' when treating patients with serious and treatment-resistant mental illnesses. When prescribing multiple medications, it is easy, however, to fall into irrational polypharmacy. We present a framework that clinicians can use to avoid the pitfall of irrational polypharmacy. When using combination therapy, clinicians should consider: (a) pharmadynamic redundancy; (b) pharmacodynamic interactions; (c) pharmacokinetic interactions; and (d) avoid inadequate dosing of medications. Clinicians should also (e) regularly reassess the need for and benefit of continued combination therapy.

Evidence of IQ-modulated association between ZNF804A gene polymorphism and cognitive function in schizophrenia patients

ZNF804A gene polymorphism rs1344706 has been suggested as the most compelling case of a candidate gene for schizophrenia by a genome-wide association study and several replication studies. The current study of 570 schizophrenia patients and 448 controls again found significantly different genotype frequencies of rs1344706 between patients and controls. More important, we found that this association was modulated by IQ, with a stronger association among individuals with relatively high IQ, which replicated results of Walters et al, 2010. We further examined whether this IQ-modulated association also existed between the SNP and the intermediate phenotypes (working memory and executive functions) of schizophrenia. Data were available from an N-back task (366 patients and 414 controls) and the attention network task (361 patients and 416 controls). We found that the SNP and IQ had significant interaction effects on the intermediate phenotypes for patients, but not for controls. The disease risk allele was associated with poorer cognitive function in patients with high IQ, but better cognitive function in patients with low IQ. Together, these results indicated that IQ may modulate the role of rs1344706 in the etiology of both schizophrenia and its cognitive impairments, and pointed to the necessity of considering general cognitive function as indexed by IQ in the future studies of genetic bases of schizophrenia.