Comparison of the single-dose pharmacokinetics and tolerability of modafinil and dextroamphetamine administered alone or in combination in healthy male volunteers

The relationship between novelty-seeking traits and behavior: Establishing construct validity for the human Behavioral Pattern Monitor

Novelty seeking is a tendency to approach new situations, putatively driven by the brain's catecholaminergic system. It is traditionally measured via self-report, but a laboratory-based paradigm, the human Behavioral Pattern Monitor (hBPM), quantifies behavior in a novel environment and has utility in cross-species studies of neuropsychiatric disorders. Our primary aim assessed whether self-reported novelty-seeking traits were associated with novelty-seeking behavior in the hBPM. An existing sample of 106 volunteers were categorized as high vs. low novelty seekers using the Temperament and Character Inventory (TCI). Subjects had been randomized to one dose of amphetamine (10 or 20 mg) or modafinil (200 or 400 mg), allowing us to explore whether a pharmacological catecholamine challenge further enhanced novelty-seeking behavior. High TCI novelty-seekers had more hBPM motor activity and novel object interactions. The exploratory analyses, although limited by low power, suggested that amphetamine and modafinil did not markedly moderate novelty-seeking traits. The hBPM demonstrates construct validity as a lab-based measure of novelty seeking and thus useful in translational studies of neuropsychiatric conditions and treatment options. Further research may illuminate whether a biological predisposition towards higher catecholaminergic activity, combined with the novelty-seeking trait, may increase propensity for risky and addictive behaviors.

Amphetamine and Clonidine Toxicity Resulting in Posterior Reversible Encephalopathy Syndrome

ABSTRACT

Amphetamine toxicity typically presents with hypertension and tachycardia. Conversely, clonidine acts as an agonist at central α2 and imidazoline receptors, which may cause brief initial hypertension followed by hypotension and bradycardia in overdose. We report a case of mixed ingestion resulting in posterior reversible encephalopathy syndrome (PRES) successfully treated with phentolamine.A 17-year-old male adolescent presented to the emergency department 2 hours after ingesting up to 25 each of clonidine 0.1-mg tablets and dextroamphetamine 10 mg extended-release capsules. He reported nausea and fatigue with initial blood pressure (BP) 145/95 mm Hg and heart rate (HR) 52 beats per minute (bpm). Nine hours postingestion (HPI), the patient developed headache, photophobia, and confusion with BP 182/111 mm Hg and HR 48 bpm. A computed tomography scan of the head revealed generalized fullness of the cerebellum, upward bulging of the tentorial leaflets, effacement of the fourth ventricle, and crowding of the foramen magnum, suspicious for an atypical presentation of PRES. The patient's systolic BP rose over 200 mm Hg and treated with 2 mg of intravenous phentolamine at 14 HPI. Blood pressure decreased to 133/82 mm Hg, and HR increased to 56 bpm with improvements in headache. Following repeat doses of phentolamine, nicardipine was initiated and increased to 2.5 mg/h for 12 hours. The patient was stable with normal vital signs at 36 HPI.The delayed presentation of hypertensive emergency with PRES may have been due to the actions of extended-release dextroamphetamine and the α2-agonistic effects of clonidine. Phentolamine was chosen for its α1-antagonism and was effective in managing symptoms.

Pharmacotherapeutic strategies for treating cocaine use disorder-what do we have to offer?

BACKGROUND

Cocaine use contines to be a significant public health problem world-wide. However, despite substantial research efforts, no pharmacotherapies are approved for the treatment of cocaine use disorder (CUD).

ARGUMENT

Studies have identified positive signals for a range of medications for treating CUD. These include long-acting amphetamine formulations, modafinil, topiramate, doxazosin and combined topiramate and mixed amphetamine salts extended-release (MAS-ER). However, valid conclusions about a medication's clinical efficacy require nuanced approaches that take into account behavioural phenotypes of the target population (frequency of use, co-abuse of cocaine and other substances, genetic subgroups, psychiatric comorbidity), variables related to the medication (dose, short-/long-acting formulations, titration speed, medication adherence) and other factors that may affect treatment outcomes. Meta-analyses frequently do not account for these co-varying factors, which contributes to a somewhat nihilistic view on pharmacotherapeutic options for CUD. In addition, the predominant focus on abstinence, which is difficult for most patients to achieve, may overshadow more nuanced therapeutic signals.

CONCLUSION

While there is an emphasis on finding new medications with novel mechanisms of action for treating CUD, currently available medications deserve further investigation based on the existing literature. Evaluating refined metrics of treatment success in well-defined subgroups of patients, and further exploring combination therapies and their synergy with behavioural/psychosocial interventions, are promising avenues to establishing effective therapies for CUD.

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.

Clinically Significant Drug-Drug Interactions with Agents for Attention-Deficit/Hyperactivity Disorder

This article provides an overview of the pharmacokinetic drug-drug interactions (DDIs) for agents prescribed for attention-deficit/hyperactivity disorder (ADHD). Polypharmacy in the treatment of patients with ADHD leads to high exposures to DDIs and possibly adverse safety outcomes. We performed a systematic search of DDI reports for ADHD agents in Embase and Medline. We also searched for agents in the pharmacological pipeline, which include (1) mazindol, molindone and viloxazine, which were previously prescribed for other indications; (2) centanafadine and AR-08, never before approved; and (3) two extracts (Polygala tenuifolia extract and the French maritime pine bark extracts). The identified literature included case reports, cross-sectional, cross-over and placebo-controlled studies of patient cohorts and healthy volunteers. The DDIs were classified as follows: ADHD agents acting as perpetrators, i.e., affecting the clearance of co-prescribed agents (victim drugs), or ADHD agents being the victim drugs, being affected by other agents. Ratios for changes in pharmacokinetic parameters before and after the DDI were used as a rough estimate of the extent of the DDI. Alcohol may increase plasma dextroamphetamine concentrations by presystemic effects. Until studies are done to orient clinicians regarding dosing changes, clinicians need to be aware of the potential for cytochrome P450 (CYP) 2D6 inhibitors to increase amphetamine levels, which is equivalent to increasing dosages. Atomoxetine is a wide therapeutic window drug. The CYP2D6 poor metabolizers who do not have CYP2D6 activity had better atomoxetine response, but also an increased risk of adverse effects. CYP2D6 inhibitors have been used to increase atomoxetine response in CYP2D6 extensive metabolizers. Guanfacine is mainly metabolized by CYP3A4, which can be induced and inhibited. The package insert recommends that in guanfacine-treated patients, after adding potent CYP3A4 inducers, the guanfacine dose should be doubled; after adding potent CYP3A4 inhibitors the guanfacine dose should be halved. Based on a phenobarbital case report and our experience with CYP3A4-metabolized antipsychotics, these correction factors may be too low. According to two case reports, carbamazepine is a clinically relevant inducer of methylphenidate (MPH). A case series study suggested that MPH may be associated with important elevations in imipramine concentrations. Due to the absence of or limitations in the data, no comments for clinicians can be provided on the pharmacokinetic DDIs for clonidine, centanafadine, mazindol, molindone, AR-08, P. tenuifolia extract and the French maritime pine bark extracts. According to currently available data, clinicians should not expect that ADHD drugs modify each other's serum concentrations. A summary table for clinicians provides our current recommendations on pharmacokinetic DDIs of ADHD agents based on our literature review and the package inserts; whenever it was possible, we provide information on serum concentrations and dose correction factors. There will be a need to periodically update these recommendations and these correction factors as new knowledge becomes available.

Pharmacokinetics of Sustained-Release Oral Dexamphetamine Sulfate in Cocaine and Heroin-Dependent Patients

INTRODUCTION

Research has shown that sustained-release (SR) dexamphetamine is a promising agonist treatment for cocaine dependence. However, little is known about the pharmacokinetics (PKs) of SR oral dexamphetamine. This study examined the PKs of a new SR dexamphetamine formulation in cocaine plus heroin-dependent patients currently in heroin-assisted treatment.

METHODS

The study was designed as an open-label PK study in 2 cohorts: n = 5 with once daily 60 mg and n = 7 with once daily 30 mg SR oral dexamphetamine. Five days of blood plasma dexamphetamine concentrations measured with liquid chromatography-mass spectrometry with PK parameter estimates using noncompartmental analysis.

RESULTS

Twelve cocaine-dependent plus heroin-dependent patients in heroin-assisted treatment were included. The initial cohort 1 dose of 60 mg once daily was adjusted to 30 mg after mild to moderate adverse events. After oral administration, tmax values (coefficient of variation %) were 6.0 (17.0%) and 6.3 (16.3%) hours and t1/2 were 11 (24.6%) and 12 (25.4%) hours for 60 mg and 30 mg SR dexamphetamine, respectively. At steady state, CSSmax values were reached at 100 (27.5%) ng/mL and 58.4 (14.4%) ng/mL, whereas CSSmin values were 39.5 (38.9%) ng/mL and 21.8 (19.8%) ng/mL for 60 mg and 30 mg, respectively.

CONCLUSIONS

The investigated SR formulation of dexamphetamine showed favorable slow-release characteristics in cocaine and heroin-dependent patients. A dose-proportional steady-state concentration was achieved within 3 days. These findings support the suitability of the SR formulation in the treatment of cocaine dependence.

Amphetamine Modestly Improves Conners' Continuous Performance Test Performance in Healthy Adults

OBJECTIVES

Amphetamine improves vigilance as assessed by continuous performance tests (CPT) in children and adults with attention deficit hyperactivity disorder (ADHD). Less is known, however, regarding amphetamine effects on vigilance in healthy adults. Thus, it remains unclear whether amphetamine produces general enhancement of vigilance or if these effects are constrained to the remediation of deficits in patients with ADHD.

METHODS

We tested 69 healthy adults (35 female) on a standardized CPT (Conner's CPT-2) after receiving 10- or 20-mg d-amphetamine or placebo. To evaluate potential effects on learning, impulsivity, and perseveration, participants were additionally tested on the Iowa Gambling Task (IGT) and Wisconsin Card Sorting Task (WCST).

RESULTS

Participants receiving placebo exhibited the classic vigilance decrement, demonstrated by a significant reduction in attention (D') across the task. This vigilance decrement was not observed, however, after either dose of amphetamine. Consistent with enhanced vigilance, the 20-mg dose also reduced reaction time variability across the task and the ADHD confidence index. The effects of amphetamine appeared to be selective to vigilance since no effects were observed on the IGT, WCST, or response inhibition/perseveration measures from the CPT.

CONCLUSIONS

The present data support the premise that amphetamine improves vigilance irrespective of disease state. Given that amphetamine is a norepinephrine/dopamine transporter inhibitor and releaser, these effects are informative regarding the neurobiological substrates of attentional control. (JINS, 2018, 24, 283-293).

Evaluation of modafinil as a perpetrator of metabolic drug-drug interactions using a model informed cocktail reaction phenotyping trial protocol

AIM

To evaluate the capacity for modafinil to be a perpetrator of metabolic drug-drug interactions by altering cytochrome P450 activity following a single dose and dosing to steady state.

METHODS

A single centre, open label, single sequence cocktail drug interaction trial. On days 0, 2 and 8 participants were administered an oral drug cocktail comprising 100 mg caffeine, 30 mg dextromethorphan, 25 mg losartan, 1 mg midazolam and 20 mg enteric-coated omeprazole. Timed blood samples were collected prior to and for up to 6 h post cocktail dosing. Between days 2 and 8 participants orally self-administered 200 mg modafinil each morning.

RESULTS

Following a single 200 mg dose of modafinil mean (± 95% CI) AUC ratios for caffeine, dextromethorphan, losartan, midazolam and omeprazole were 0.95 (± 0.08), 1.01 (± 0.35), 0.97 (± 0.10), 0.98 (± 0.10) and 1.36 (± 0.06), respectively. Following dosing of modafinil to steady state (200 mg for 7 days), AUC ratios for caffeine, dextromethorphan, losartan, midazolam and omeprazole were 0.90 (± 0.16), 0.79 (± 0.09), 0.98 (± 0.11), 0.66 (± 0.12) and 1.90 (± 0.53), respectively.

CONCLUSIONS

These data support consideration of the risk of clinically relevant metabolic drug-drug interactions perpetrated by modafinil when this drug is co-administered with drugs that are primarily cleared by CYP2C19 (single modafinil dose or steady state modafinil dosing) or CYP3A4 (steady state modafinil dosing only) catalysed metabolic pathways.

Synthesis of (R)-Modafinil via Organocatalyzed and Non-Heme Iron-Catalyzed Sulfoxidation Using H2O2 as an Environmentally Benign Oxidant

The first organocatalyzed sulfoxidation reaction towards enantioenriched (R)-modafinil (Armodafinil®), a drug against narcolepsy, is reported here. A series of chiral organocatalysts, e.g., different chiral BINOL-phosphates, or a fructose-derived N-substituted oxazolidinone ketone (Shi catalyst) were applied for the sulfoxidation reaction with environmentally friendly H2O2 as a convenient oxygen transferring agent. Furthermore, the potential of a biomimetic catalytic system consisting of FeCl3 and a dipeptide-based chiral ligand was demonstrated, which constitutes the most successful asymmetric non-heme iron-catalyzed synthesis of (R)-modafinil so far.

Optimized Cocktail Phenotyping Study Protocol Using Physiological Based Pharmacokinetic Modeling and In silico Assessment of Metabolic Drug-Drug Interactions Involving Modafinil

In vivo cocktail pathway phenotyping (ICPP) is routinely used to assess the metabolic drug-drug interaction (mDDI) potential of new drug candidates (NDC) during drug development. However, there are a number of potential limitations to this approach and the use of validated drug cocktails and study protocols is essential. Typically ICPP mDDI studies assess only the impact of interactions following multiple postulated perpetrator doses and hence the emphasis in terms of validation of these studies has been ensuring that there are no interactions between probe substrates. Studies assessing the comparative impact of single and multiple doses of the postulated perpetrator have the potential to provide richer information regarding both the clinical impact and mechanism of mDDIs. Using modafinil as a model compound, we sought to develop an optimized ICPP mDDI study protocol to evaluate the potential magnitude and clinical relevance of mDDIs using a physiologically based pharmacokinetic modeling approach.

Amphetamine increases activity but not exploration in humans and mice

RATIONALE

Cross-species quantification of physiological behavior enables a better understanding of the biological systems underlying neuropsychiatric diseases such as bipolar disorder (BD). Cardinal symptoms of manic BD include increased motor activity and goal-directed behavior, thought to be related to increased catecholamine activity, potentially selective to dopamine homeostatic dysregulation.

OBJECTIVES

The objective of this study was to test whether acute administration of amphetamine, a norepinephrine/dopamine transporter inhibitor and dopamine releaser, would replicate the profile of activity and exploration observed in both humans with manic BD and mouse models of mania.

METHODS

Healthy volunteers with no psychiatric history were randomized to a one-time dose of placebo (n = 25), 10 mg d-amphetamine (n = 18), or 20 mg amphetamine (n = 23). Eighty mice were administered one of four doses of d-amphetamine or vehicle. Humans and mice were tested in the behavioral pattern monitor (BPM), which quantifies motor activity, exploratory behavior, and spatial patterns of behavior.

RESULTS

In humans, the 20-mg dose of amphetamine increased motor activity as measured by acceleration without marked effects on exploration or spatial patterns of activity. In mice, amphetamine increased activity, decreased specific exploration, and caused straighter, one-dimensional movements in a dose-dependent manner.

CONCLUSIONS

Consistent with mice, amphetamine increased motoric activity in humans without increasing exploration. Given that BD patients exhibit heightened exploration, these data further emphasize the limitation of amphetamine-induced hyperactivity as a suitable model for BD. Further, these studies highlight the utility of cross-species physiological paradigms in validating biological mechanisms of psychiatric diseases.

Relationship between discriminative stimulus effects and plasma methamphetamine and amphetamine levels of intramuscular methamphetamine in male rhesus monkeys

Methamphetamine is a globally abused drug that is metabolized to amphetamine, which also produces abuse-related behavioral effects. However, the contributing role of methamphetamine metabolism to amphetamine in methamphetamine's abuse-related subjective effects is unknown. This preclinical study was designed to determine 1) the relationship between plasma methamphetamine levels and methamphetamine discriminative stimulus effects and 2) the contribution of the methamphetamine metabolite amphetamine in the discriminative stimulus effects of methamphetamine in rhesus monkeys. Adult male rhesus monkeys (n=3) were trained to discriminate 0.18mg/kg intramuscular (+)-methamphetamine from saline in a two-key food-reinforced discrimination procedure. Time course of saline, (+)-methamphetamine (0.032-0.32mg/kg), and (+)-amphetamine (0.032-0.32mg/kg) discriminative stimulus effects were determined. Parallel pharmacokinetic studies were conducted in the same monkeys to determine plasma methamphetamine and amphetamine levels after methamphetamine administration and amphetamine levels after amphetamine administration for correlation with behavior in the discrimination procedure. Both methamphetamine and amphetamine produced full, ≥90%, methamphetamine-like discriminative stimulus effects. Amphetamine displayed a slightly, but significantly, longer duration of action than methamphetamine in the discrimination procedure. Both methamphetamine and amphetamine behavioral effects were related to methamphetamine and amphetamine plasma levels by a clockwise hysteresis loop indicating acute tolerance had developed to the discriminative stimulus effects. Furthermore, amphetamine levels after methamphetamine administration were absent when methamphetamine stimulus effects were greatest and peaked when methamphetamine discriminative stimulus effects returned to saline-like levels. Overall, these results demonstrate the methamphetamine metabolite amphetamine does not contribute to methamphetamine's abuse-related subjective effects.

Rationalization and prediction of in vivo metabolite exposures: the role of metabolite kinetics, clearance predictions and in vitro parameters

IMPORTANCE OF THE FIELD

Due to growing concerns over toxic or active metabolites, significant efforts have been focused on qualitative identification of potential in vivo metabolites from in vitro data. However, limited tools are available to quantitatively predict their human exposures.

AREAS COVERED IN THIS REVIEW

Theory of clearance predictions and metabolite kinetics is reviewed together with supporting experimental data. In vitro and in vivo data of known circulating metabolites and their parent drugs were collected and the predictions of in vivo exposures of the metabolites were evaluated.

WHAT THE READER WILL GAIN

The theory and data reviewed will be useful in early identification of human metabolites that will circulate at significant levels in vivo and help in designing in vivo studies that focus on characterization of metabolites. It will also assist in rationalization of metabolite-to-parent ratios used as markers of specific enzyme activity.

TAKE HOME MESSAGE

The relative importance of a metabolite in comparison to the parent compound as well as other metabolites in vivo can only be predicted using the metabolite's in vitro formation and elimination clearances, and the in vivo disposition of a metabolite can only be rationalized when the elimination pathways of that metabolite are known.

Modafinil: a review of neurochemical actions and effects on cognition

Modafinil (2-[(Diphenylmethyl) sulfinyl] acetamide, Provigil) is an FDA-approved medication with wake-promoting properties. Pre-clinical studies of modafinil suggest a complex profile of neurochemical and behavioral effects, distinct from those of amphetamine. In addition, modafinil shows initial promise for a variety of off-label indications in psychiatry, including treatment-resistant depression, attention-deficit/hyperactivity disorder, and schizophrenia. Cognitive dysfunction may be a particularly important emerging treatment target for modafinil, across these and other neuropsychiatric disorders. We aimed to comprehensively review the empirical literature on neurochemical actions of modafinil, and effects on cognition in animal models, healthy adult humans, and clinical populations. We searched PubMed with the search term 'modafinil' and reviewed all English-language articles for neurochemical, neurophysiological, cognitive, or information-processing experimental measures. We additionally summarized the pharmacokinetic profile of modafinil and clinical efficacy in psychiatric patients. Modafinil exhibits robust effects on catecholamines, serotonin, glutamate, gamma amino-butyric acid, orexin, and histamine systems in the brain. Many of these effects may be secondary to catecholamine effects, with some selectivity for cortical over subcortical sites of action. In addition, modafinil (at well-tolerated doses) improves function in several cognitive domains, including working memory and episodic memory, and other processes dependent on prefrontal cortex and cognitive control. These effects are observed in rodents, healthy adults, and across several psychiatric disorders. Furthermore, modafinil appears to be well-tolerated, with a low rate of adverse events and a low liability to abuse. Modafinil has a number of neurochemical actions in the brain, which may be related to primary effects on catecholaminergic systems. These effects are in general advantageous for cognitive processes. Overall, modafinil is an excellent candidate agent for remediation of cognitive dysfunction in neuropsychiatric disorders.

Smoked cocaine self-administration is decreased by modafinil

Modafinil has been reported to reduce cocaine use in a clinical sample of infrequent users (2 days/week), but the effects of modafinil on cocaine self-administration in the laboratory have not been studied. The present study investigated the effects of modafinil maintenance on cocaine self-administration by frequent users (4 days/week) under controlled laboratory conditions. During this 48-day double-blind, crossover design study, the effects of modafinil maintenance (0, 200, and 400 mg/day) on response to smoked cocaine (0, 12, 25, and 50 mg) were examined in nontreatment-seeking cocaine-dependent individuals (n=8). Cocaine significantly increased self-administration, subjective-effect ratings, and cardiovascular measures; modafinil at both doses (200 and 400 mg/day) markedly attenuated these effects. These findings agree with data from previous human laboratory and clinical investigations of modafinil as a potential cocaine abuse treatment medication. Thus, our data support the potential of modafinil as a pharmacotherapy for cocaine dependence.

Comparison of diphenhydramine and modafinil on arousal and autonomic functions in healthy volunteers

Arousal is regulated by the interplay between wakefulness- and sleep-promoting nuclei. Major wakefulness-promoting nuclei are the histaminergic tuberomamillary nucleus (TMN) of the hypothalamus and the noradrenergic locus coeruleus (LC) of the pons, which also play a role in autonomic regulation. First generation antihistamines, such as diphenhydramine, are likely to cause sedation by blocking excitatory H1 histamine receptors in the cerebral cortex, and the anti-narcolepsy drug modafinil may promote wakefulness by activating the locus coeruleus. We compared the effects of single doses of diphenhydramine (75 mg) and modafinil (200 mg) on arousal and autonomic functions in 16 healthy male volunteers, using a placebo-controlled, balanced, double-blind design. Arousal was assessed by critical flicker fusion frequency (CFFF), visual analogue scales (VAS) and pupillary fatigue waves (Pupillographic Sleepiness Test (PST)). Autonomic functions measured included resting pupil diameter, light and darkness reflex responses, blood pressure, heart rate and salivation. Data were analysed with ANOVA, with multiple comparisons. Diphenhydramine had sedative effects as shown by reductions in CFFF, VAS alertness ratings and increases of the indices of pupillary fatigue. Modafinil had alerting effects as indicated by reductions in the measures of pupillary fatigue. Comparison of pre-post medication changes in pupil diameter showed a decrease after diphenhydramine and an increase after modafinil. Diphenhydramine reduced salivation, and modafinil increased systolic blood pressure. In conclusion, diphenhydramine and modafinil evoked opposite effects on arousal and sympathetic functions, which are likely to reflect their interaction with the central histaminergic and noradrenergic systems. Hyposalivation by diphenhydramine is likely to be due to its additional anticholinergic property.

Modafinil and cocaine interactions

This Phase I trial evaluated the interaction between modafinil steady-state and cocaine. Twelve non-treatment seeking, cocaine dependent volunteers received four sets of randomized blinded infusions of saline, 20 mg IV cocaine, and 40 mg IV cocaine. Modafinil was given open label at 0 mg, 400 mg, or 800 mg. Modafinil combined with IV cocaine did not result in any significant hemodynamic interactions. Modafinil significantly dampened scores on Visual Analog Scale measures as compared to baseline cocaine conditions. No significant alterations in labs occurred. Further outpatient trials of modafinil appear to be warranted.

Modafinil influences the pharmacokinetics of intravenous cocaine in healthy cocaine-dependent volunteers

OBJECTIVE

To determine if modafinil, a putative treatment for cocaine dependence, influences the pharmacokinetics of intravenous cocaine in otherwise healthy cocaine-dependent volunteers.

METHODS

Cocaine 20 or 40 mg was administered intravenously on consecutive days over 1 minute at baseline and after modafinil administration at each of two dosages of 400 and 800 mg/day for 7 days.

RESULTS

Twelve subjects completed the clinical protocol. Compared with baseline, the cocaine peak plasma concentration was decreased after both the 20 and 40 mg cocaine infusions, but the reduction was only statistically significant after the 40 mg cocaine infusion (p < 0.01 after modafinil 400 mg/day; p < 0.05 after modafinil 800 mg/day). The area under the cocaine plasma concentration-time curve from 0 to 180 minutes (AUC180) was significantly decreased by modafinil administration (p < 0.01 and p < 0.001 for modafinil 400 and 800 mg/day, respectively, for the cocaine 20mg dose; p < 0.001 for the cocaine 40 mg dose at both modafinil levels). There were no significant changes in total AUC, clearance or elimination half-life of cocaine.

CONCLUSION

This study did not find evidence for a harmful pharmacokinetic interaction between modafinil and cocaine. In contrast, long-term administration of modafinil significantly decreased systemic exposure to cocaine during the first 180 minutes following intravenous cocaine administration.

Modafinil: new indications for wake promotion

In January 2004, the wake-promoting agent, modafinil, was approved in the US for the treatment of excessive sleepiness (ES) associated with obstructive sleep apnoea/hypopnoea syndrome (OSAHS) and shift-work sleep disorder (SWSD), representing an expansion of its labelling from the initial indication for ES associated with narcolepsy. A total of five randomised, placebo-controlled studies in these three disorders showed statistically significant benefits on various objective measures and subjective estimates of ES, including the Multiple Sleep Latency Test, Maintenance of Wakefulness Test, Epworth Sleepiness Scale and Karolinska Sleepiness Scale. Significant improvement was also seen in overall clinical condition (on the Clinical Global Impression of Change) and measures of sustained attention and reaction time (on the Psychomotor Vigilance Task). The clinical efficacy of modafinil, combined with improved safety over CNS stimulants, has made it the most prescribed medication for the treatment of ES associated with narcolepsy. Modafinil is the only medication approved for ES associated with OSAHS and SWSD (for OSAHS, it is indicated as an adjunct to standard treatments for the under-lying obstruction). Unlike many other medications used for ES, modafinil is not known to be abused. The most common adverse event reported in clinical studies was headaches; most were transient and mild-to-moderate in severity. Modafinil also has the potential for interactions with other drugs metabolised via cytochrome P450 enzyme pathways. Potential obstacles to the use of modafinil include an under-recognition of ES and its consequences. Increased education, both of the public and the medical community, should improve the recognition and therapy of ES.

Detection of modafinil in human urine by gas chromatography–mass spectrometry

The main purpose of this study was to detect and quantify modafinil in human urine by gas chromatography-mass spectrometry (GC-MS). Urinary samples were collected from three healthy male volunteers following oral administration of a clinical dose (100 mg) of modafinil (Provigil). Urine specimens were extracted with t-butylmethyl ether (TBME) prior to GC-MS analysis. The results demonstrate that the chromatographic characteristics and the mass spectrum of the unchanged parent drug extracted from urine samples were identical to that obtained from the authentic standard. The times for the unchanged modafinil to reach peak concentration in the urine of the three volunteers were at 2 h (6.14 microg/mL), 4 h (9.93 microg/mL) and 8 h (3.58 microg/mL), respectively. Total clearance occurred in approximately 48-72 h with 2-5% eliminated through urine as unchanged modafinil. The present study demonstrates that modafinil is detectable in the absence of hydrolysis and derivatization steps.

Modafinil Elicits Sympathomedullary Activation

The autonomic effects of modafinil (Provigil), a psychostimulant widely used to attenuate fatigue and promote wakefulness, are currently unexplored. We assessed the effect of modafinil on autonomic nervous system. We compared oral modafinil (400 mg×1) versus placebo in 12 healthy hospitalized normal subjects in a randomized double-blind, placebo-controlled cross-over study for 3 days each with subjects in 150 mEq sodium, 70 mEq potassium balance at the Vanderbilt General Clinical Research Center. Modafinil increased resting heart rate (9.2±2.0 bpm; mean [±SE]; 95% confidence interval [CI], 4.7 to 13.6; P =0.001), resting systolic blood pressure (7.3±3.2 mm Hg; 95% CI, 0.2 to 14.4; P =0.044), and resting diastolic blood pressure (5.3±1.7 mm Hg; 95% CI, 1.4 to 9.1 mm Hg; P <0.012). Modafinil elicited a 42% higher orthostatic increase in plasma norepinephrine (0.8±0.3 nmol/L; 95% CI, 0.2 to 1.3; P =0.01), and caused a 33% increase in urine norepinephrine (5.1±1.1 nmol/L creatinine per day; 95% CI, 2.7 to 7.4, P =0.001), and an 81% increase in urine epinephrine (1.3±0.2 nmol/L creatinine per day; 95% CI, 1 to 2; P <0.001). The peroneal microneurographic sympathetic activity was attenuated by modafinil during orthostatic tilt ( P <0.001). α1-Adrenoreceptor function was maintained. Modafinil substantially perturbs autonomic cardiovascular regulation by increase in heart rate and blood pressure. Autonomic changes of this magnitude encourage caution in use of modafinil in patients with cardiovascular disease.

Pharmacotherapy for excessive daytime sleepiness

Excessive daytime sleepiness (EDS) has recognized detrimental consequences such as road traffic accidents, impaired psychological functioning and reduced work performance. EDS can result from multiple causes such as sleep deprivation, sleep fragmentation, neurological, psychiatric and circadian rhythm disorders. Treating the underlying cause of EDS remains the mainstay of therapy but in those who continue to be excessively sleepy, further treatment may be warranted. Traditionally, the amphetamine derivatives, methylphenidate and pemoline (collectively sympathomimetic) psychostimulants were the commonest form of therapy for EDS, particularly in conditions such as narcolepsy. More recently, the advent of modafinil has broadened the range of therapeutic options. Modafinil has a safer side-effect profile and as a result, interest in this drug for the management of EDS in other disorders, as well as narcolepsy, has increased considerably. There is a growing school of thought that modafinil may have a role to play in other indications such as obstructive sleep apnea/hypopnea syndrome already treated by nasal continuous positive airway pressure but persisting EDS, shift work sleep disorders, neurological causes of sleepiness, and healthy adults performing sustained operations, particularly those in the military. However, until adequately powered randomised-controlled trials confirm long-term efficacy and safety, the recommendation of wakefulness promoters in healthy adults cannot be justified.

Modafinil in the treatment of excessive daytime sleepiness in children

BACKGROUND

Modafinil is an alerting agent approved for the treatment of narcolepsy in adults. There are no studies examining the long-term effects and safety profile of modafinil in children with excessive daytime somnolence (EDS).

OBJECTIVES

To determine the effects of modafinil on clinical manifestations of narcolepsy and idiopathic hypersomnia.

METHODS

A systematic chart review was conducted for 13 children (mean age 11.0+/-5.3 years, six males, 10 with narcolepsy and three with idiopathic hypersomnia) receiving modafinil.

RESULTS

The mean modafinil dose was 346+/-119 mg/day, with a mean treatment duration of 15.6+/-7.8 months. For approximately 90% of the children treated, parents reported a favorable response with the reduction in sudden sleep attacks, as documented by sleep-wake diaries. One child failed to improve on 400 mg/day modafinil and was switched to methylphenidate. Two other children showed only partial improvement and required additional stimulant medication to control EDS symptoms. Seven children underwent repeated nocturnal polysomnography and multiple sleep latency tests (MSLT). Compared to baseline MSLT measures (mean sleep latency: 6.6+/-3.7 min), modafinil prolonged mean sleep latency (10.2+/-4.8 min, p=0.02) without significant alteration in nocturnal polysomnographic measures. However, a trend towards REM sleep reduction was noted (16.8+/-5.1%TST vs. 11.8+/-6.2%TST). Exacerbation of seizures and psychotic symptoms was reported with modafinil therapy in two children with preexisting conditions. Hematological and hepatic functions assessed every 3 months remained unaltered.

CONCLUSION

Modafinil has a modest, yet significant effect on EDS in children and appears to be safe and well tolerated.

Drugs for Stroke Recovery

Clinical trials of pharmacological agents in stroke have mainly focused on events that need to be modified in the very acute stage, such as restoration of blood flow with thrombolytic therapy or reducing the effects of ischaemia with neuroprotective therapy. Thrombolytic therapy is, however, only effective within the first few hours of stroke onset and so far, no neuroprotective therapy has proven to be efficacious in humans. Thus, there is a great need for new pharmacological strategies to improve outcome after stroke. Accumulating evidence supports the assumption that the brain is plastic and improvements can be expected after permanent injuries. Acute and chronic alterations in neurotransmitter regulation after injury affects plasticity and may thus provide a basis for new pharmacological targets for stroke recovery. The search for pharmacological therapies that affect the recovery process after a permanent injury has been intensified during the last decade. Amphetamines, in combination with training, are currently one of the most promising pharmacological strategies studied for recovery after stroke. Several non-mutually exclusive hypotheses, more or less supported by experimental studies, have tried to explain the mechanisms underlying the facilitation of recovery of function with amphetamine treatment. Amphetamines are believed to hasten the processes in the brain, such as plasticity mechanisms and resolution of diaschisis. The combination of amphetamine and task-specific training seems to be of importance to the outcome. Results from animal studies are consistent between different models and species, and mainly show an increased rate of recovery but there are a few exceptions, with some studies reporting no effect or even a decreased recovery rate. In humans the number of randomised controlled studies of amphetamines is growing rapidly. Results from a Cochrane systematic review indicate a faster motor and language recovery rate with treatment, but the number of studies is too few and studies are too small to draw definite conclusions about the effect on recovery of stroke. Data in the systematic review also indicate that the mortality rate is higher in amphetamine-treated patients compared with placebo-treated patients. However, this is most likely because of baseline imbalances between the treatment groups with patients with more severe strokes being allocated to amphetamine treatment. Further clinical trials are justified, but at present amphetamines should not be used in clinical practice.

Pharmacokinetics of Dexamphetamine in Acute Stroke

Pharmacokinetics of dexamphetamine was studied in 26 patients with cerebral infarct, aged 37 to 84 years. Capsules were administered orally twice daily (at 8 am and 12 am) in three doses (2.5 mg, 5 mg, and 10 mg) for 5 consecutive days (day 1 to day 5). Blood samples were collected immediately before and 1, 2, 3, 4, 5, 6, 7, 8, and 9 hours after first administration on day 1 and before, and 4 and 8 hours after administration on days 2 through 5. The dose normalized area under the plasma concentration time curve, AUC/mg/kg, was only correlated with s-creatinine (P = 0.013) but not with age, sex, body mass index, neurologic prognosis, or dose (mg/kg), as established by multiple stepwise linear regression. The median terminal half life time was 14.3 hours (inter quartile range, IQR: 11.9-6.9), 13.1 (IQR: 10.8-15.9) and 14.0 (IQR: 7.4-16.4) in the 2.5 mg, 5 mg, and 10 mg groups, respectively. The median maximal plasma concentration (Cmax) was 6.6 ng/mL (IQR: 5.1-7.0), 11.6 (IQR: 7.8-12.8), and 16.9 (IQR: 14.9-20.2) in the 2.5 mg, 5 mg, and the 10 mg groups, respectively. Differences in Cmax between the 2.5 mg and 10 mg group were significant (P < 0.001). The median time to Cmax (Tmax) was 1.83 hours (IQR: 1.79-3.94), 2.59 (IQR: 1.32-3.83), and 3.86 (IQR: 1.82-5.77) in the 2.5, 5, and 10 mg groups, respectively. In the present patient population, a predetermined AUC value can be obtained by a dosing regimen of dexamphetamine based on body weight (ie, mg/kg), with precautions for patients with elevated s-creatinine.

Modafinil in children with attention-deficit hyperactivity disorder

Previous clinical evidence suggested that modafinil may improve clinical features of children with attention-deficit hyperactivity disorder. To test this hypothesis, a randomized, double-blind, placebo-controlled study design was used. Of 24 children initially randomized into the study, 11 control subjects and 11 treatment patients completed the study, with evaluation before medication and after 5 to 6 weeks. The average Test of Variables of Attention attention-deficit hyperactivity disorder z score improved by 2.53 S.D.s for the modafinil group compared with a decline of 1.02 for control patients (P < or = 0.02). Conners Rating Scales ADHD total t scores for the modafinil group improved from 76.6 to 68.2 compared with improvement from 77.7 to 76.0 for control subjects (P = 0.04). Ten of 11 treatment patients were reported as "significantly" improved, whereas eight of 11 control subjects were reported as manifesting "no" or "slight" improvement (P < 0.001). Adverse effects were few and manageable, with no anorexia. Modafinil may be a useful treatment for children with ADHD, particularly when anorexia limits use of stimulants.

Modafinil and cocaine: a double-blind, placebo-controlled drug interaction study

Modafinil is a novel compound that is approved for the treatment of narcolepsy. It is now being studied as a potential treatment for cocaine dependence. Cocaine withdrawal symptoms are associated with poor clinical outcome and are likely to be reversed by modafinil. In addition, the neurotransmitter actions of modafinil are opposite to cocaine-induced neuroadaptations affecting dopamine and glutamate reward circuits. Since cocaine-dependent subjects might use cocaine during a clinical trial with modafinil, this study tested the safety of intravenous cocaine (30 mg) in combination with modafinil. Each of seven subjects received a baseline (open-label) cocaine infusion. Three subsequent cocaine infusions were administered after subjects received 4 days of low dose modafinil (200 mg/day), high dose modafinil (400 mg/day), or placebo in randomized double-blind sequences. One subject received placebo prior to all infusions. Our results indicate that co-administering modafinil and a single dose of intravenous cocaine is not associated with medical risk in terms of blood pressure, pulse, temperature, or electrocardiogram measures. Furthermore, pretreatment with modafinil did not intensify cocaine euphoria or cocaine-induced craving. In fact, cocaine euphoria was significantly blunted (P=0.02) in one of our subjective measures.

Clinical pharmacokinetic profile of modafinil

Modafinil is a unique wake-promoting agent for oral administration. Its pharmacological properties are distinct from those of other CNS agents, and it selectively targets neuronal pathways in the sleep/wake centres of the brain. After single or multiple oral doses, modafinil is readily absorbed, reaching maximum plasma concentrations at 2-4 hours after administration and pharmacokinetic steady state within 2-4 days. Its pharmacokinetics are dose-independent between 200 and 600 mg/day. The elimination half-life is approximately 12-15 hours, which is largely reflective of the pharmacokinetics of the longer-lived l-enantiomer. Modafinil is primarily eliminated via metabolism, mainly in the liver, with subsequent excretion in the urine. Less than 10% of the dose is excreted as unchanged drug. Metabolism is largely via amide hydrolysis, with lesser contributions from cytochrome P450 (CYP)-mediated oxidative pathways. In patients who are renally or hepatically compromised, the elimination processes can be slowed, and in a similar manner (although to a lesser extent), elimination in the elderly may be reduced due to normal effects of aging. Because modafinil is administered concomitantly with other medications, the potential for metabolic drug-drug interactions has been examined both in vitro and in vivo. In vitro, modafinil was observed to produce a reversible inhibition of CYP2C19 in human liver microsomes. It also caused a small, but concentration-dependent, induction of CYP1A2, CYP2B6 and CYP3A4 activities and suppression of CYP2C9 activity in primary cultures of human hepatocytes. Clinical studies have been conducted to examine the potential for interactions with methylphenidate, dexamfetamine, warfarin, ethinylestradiol and triazolam. The only substantive interactions observed were with ethinylestradiol and triazolam, apparently through induction of CYP3A4, primarily in the gastrointestinal system. Overall, the results of the interaction studies suggest that modafinil has potential to affect the pharmacokinetics of drugs that are metabolised by certain CYP enzymes. Compounds that induce or inhibit CYP activity are unlikely to have major effects on the pharmacokinetics of modafinil. In summary, the results show that modafinil is a moderately long-lived drug that is well absorbed and extensively metabolised.

Chiral analysis of d- and l-modafinil in human serum: application to human pharmacokinetic studies

Modafinil is a novel stimulant approved by the FDA for use in the management of excessive sleepiness associated with narcolepsy. Utility for other indications includes attention deficit-hyperactivity disorder (ADHD), depression, and management of cocaine dependence. To investigate the pharmacokinetics of modafinil in these patients, the authors improved and validated an HPLC method to separate and quantitate the separate enantiomers of modafinil in human serum. d- and l-Modafinil and the internal standard 3,3-diphenylpropylamine were extracted from serum, separated by gradient elution on a beta-cyclodextrin column, and then detected by UV absorbance at 225 nm. The elution gradient was developed to eliminate interferences by other drugs used to manage narcolepsy, ADHD, and stimulants of abuse, and endogenous substances in human serum. Validation studies included determination of stability, selectivity, precision, accuracy, and recovery. The method was used to investigate the pharmacokinetics of d- and l-modafinil in a volunteer after receiving 400 mg twice daily of racemic modafinil for 5 days. Interday and intraday assay variability (CV) typically ranged from 3% to 4%. The limits of detection (0.01 microg/mL) and quantitation (0.5 microg/mL) were well below the concentration expected in serum from patients receiving therapeutic doses of modafinil. The method was free from interference by methylphenidate, cocaine, commonly used antidepressants, and amphetamines. An example of apparent stereoselective disposition is presented as d-modafinil was eliminated more rapidly than l-modafinil from human serum. The validation data support the use of this method for human pharmacokinetic studies of modafinil in patients with known or suspected use of common antidepressants, psychostimulants, and drugs of abuse.

Enantioselective trace analysis of amphetamine in human plasma by gas chromatography/negative ion chemical ionization mass spectrometry

A method for the quantitative enantioselective analysis of amphetamine in human plasma by gas chromatography/negative ion chemical ionization mass spectrometry (GC/NICI-MS) is presented. Five-fold deuterated analogues of both enantiomers were used as internal standard. Plasma sample preparation was performed by a rapid liquid-liquid extraction using n-hexane. Derivatization with (S)-(-)-N-(heptafluorobutyryl)prolyl chloride was accomplished directly in the n-hexane extract to avoid loss of amphetamine during sample concentration. The method was validated in the expected concentration range of 0.006 for a pharmacokinetic study. Calibration curves were linear within a range 0.006-50 ng/mL plasma. Precision and accuracy were acceptable over the entire calibration range. Baseline separation of the enantiomers was easily achieved on a 15-m nonchiral apolar column. The method is simple and robust, and has been applied to the batch analysis of amphetamine enantiomers.

Determination of modafinil, modafinil acid and modafinil sulfone in human plasma utilizing liquid-liquid extraction and high-performance liquid chromatography

An assay was developed to determine concentrations of modafinil (dl-2-[(diphenylmethyl)sulfinyl]acetamide; Provigil) and its two major circulating metabolites, modafinil acid and modafinil sulfone, in human plasma. The assay utilized liquid-liquid extraction of the analytes and an internal standard, (phenylthio)acetic acid, from plasma into a mixture of hexane-dichloromethane-glacial acetic acid (55:45:2, v/v). The analytes were resolved isocratically on a narrow-bore phenyl column at a mobile phase flow-rate of 0.3 ml/min and were monitored by UV detection at 235 nm. The method reported herein reduces the required sample volume of previously reported methods from 1.00 to 0.200 ml of plasma while lowering the limit of quantification (LOQ). The linear range of the assay was from 0.100 to 20.0 microg/ml for each of the three compounds.

Effects of modafinil in children with attention-deficit/hyperactivity disorder: an open-label study

OBJECTIVE

To examine the effect of once-daily dosing of modafinil, a stimulant that has a long duration of action, on clinical features of attention-deficit/hyperactivity disorder (ADHD) in children.

METHOD

An open-label design was used to compare the Conners Parent and Teacher Rating Scale-Revised (L) (CPRS, CTRS), the ADHD Rating Scale-IV, and the Test of Variables of Attention (TOVA), without and with medication, in children with ADHD. Eleven children with ADHD, ranging in age from 5 to 15 years, took modafinil for an average of 4.6 weeks.

RESULTS

Average TOVA ADHD scores improved by 2.43 SD (p = .0009). CTRS and CPRS ADHD index T scores improved by an average of 14.1 (p = .0009) and 17.7 points (p = .001), respectively. The mean ADHD Rating Scale-IV scores improved from the 88th percentile to the 75th percentile (p = .047). One subject withdrew from the study because of an adverse event that was resolved completely with medication withdrawal. Other side effects were mild and responded to dose adjustment. No subjects required more than one dose per day.

CONCLUSIONS

Modafinil may be a useful once-daily treatment for children with ADHD. Further study using a double-blind, placebo-controlled design is needed.