Efficacy of dexmethylphenidate for the treatment of fatigue after cancer chemotherapy: a randomized clinical trial

Cancer and its treatment can induce subjective and objective evidence of diminished functional capacity encompassing physical fatigue and cognitive impairment. Dexmethylphenidate (D-MPH; the D-isomer of methylphenidate) was evaluated for treatment of chemotherapy-related fatigue and cognitive impairment. A randomized, double-blind, placebo-controlled, parallel-group study evaluated the potential therapeutic effect and safety of D-MPH in the treatment of patients with chemotherapy-related fatigue. Change from baseline in the Functional Assessment of Chronic Illness Therapy-Fatigue Subscale (FACIT-F) total score at Week 8 was the primary outcome measure. One hundred fifty-four patients (predominantly with breast and ovarian cancers) were randomized and treated. Compared with placebo, D-MPH-treated subjects demonstrated a significant improvement in fatigue symptoms at Week 8 in the FACIT-F (P=0.02) and the Clinical Global Impression-Severity scores (P=0.02), without clinically relevant changes in hemoglobin levels. Cognitive function was not significantly improved. There was a higher rate of study drug-related adverse events (AEs) (48 of 76 [63%] vs. 22 of 78 [28%]) and a higher discontinuation rate because of AEs (8 of 76 [11%] vs. 1 of 78 [1.3%]) in D-MPH-treated subjects compared with placebo-treated subjects. The most commonly reported AEs independent of study drug relationship in D-MPH-treated subjects were headache, nausea, and dry mouth, and in placebo-treated subjects were headache, diarrhea, and insomnia. D-MPH produced significant improvement in fatigue in subjects previously treated with cytotoxic chemotherapy. Further studies with D-MPH or other agents to explore treatment response in chemotherapy-associated fatigue should be considered.

Efficacy and safety of dexmethylphenidate extended-release capsules in adults with attention-deficit/hyperactivity disorder

BACKGROUND

This multicenter, randomized, fixed-dose, double-blind, placebo-controlled study evaluated efficacy of extended-release dexmethylphenidate (d-MPH-ER) in adults with attention-deficit/hyperactivity disorder (ADHD).

METHODS

Randomized adults with ADHD (n=221) received once-daily d-MPH-ER 20 mg, 30 mg, or 40 mg or placebo for 5 weeks. The primary efficacy variable was change from baseline to final visit in DSM-IV ADHD Rating Scale (ADHD-RS) total score. Secondary efficacy parameters included the proportion of patients with improvement>or=30% in ADHD-RS total score and final scores on Clinical Global Impressions-Improvement (CGI-I) scale.

RESULTS

Of 218 evaluable patients, 184 completed the study. All d-MPH-ER doses were significantly superior to placebo in improving ADHD-RS total scores. Placebo scores improved by 7.9; d-MPH-ER, 20 mg, improved by 13.7 (p=.006); d-MPH-ER, 30 mg, improved by 13.4 (p=.012); and d-MPH-ER, 40 mg, improved by 16.9 (p<.001). Overall distribution of CGI-I ratings at final visit was significantly better with each d-MPH-ER dosage than with placebo. There were no unexpected safety or tolerability concerns, based on experience with racemic methylphenidate (MPH) in adults and dexmethylphenidate (d-MPH) in children.

CONCLUSIONS

Once-daily d-MPH-ER at 20 mg, 30 mg, or 40 mg is a safe and effective treatment for adults with ADHD.

A comprehensive in vitro screening of d-, l-, and dl-threo-methylphenidate: an exploratory study

dl-Methylphenidate (MPH) has been widely used to treat attention-deficit/hyperactivity disorder (ADHD) for the last half century. It had been exclusively available in the racemic form, i.e., a 50:50 mixture of d- and l-isomers. However, a single enantiomer formulation, d-MPH (dexmethylphenidate), became available for general clinical use in 2002. For this reason, the intrinsic pharmacological differences in the effects of d- and l-MPH have recently come under intense investigation. The primary therapeutic effects of MPH are generally recognized to reside in the d-isomer. The present investigation provides quantitative values for a broad range of receptor-level interactions of the individual MPH isomers to better characterize the distinction between dl-MPH versus d-MPH versus l-MPH as it relates to binding affinity at sites associated with relevant central nervous system (CNS) pharmacology, as well as peripheral physiology. Overall, there were few differences in binding affinities between d-MPH and the racemate whereas there were more apparent differences between d-MPH and l-MPH. d-MPH exhibited prominent affinity at the norepinephrine transporter (NET) site, even exceeding such affinity at the dopamine transporter (DAT). These results further demonstrate that affinity for catecholaminergic sites largely resides in the d-MPH isomer. Although binding affinity was not demonstrable at the serotonin (5-HT) transporter site (SERT), novel findings of the study included affinity for the 5-HT1A and 5-HT2B receptor sites for both d- and l-MPH, with d-MPH exerting by far the most predominant effects at these sites. Thus, the emerging data of favorable therapeutic effects of ADHD treatment with d-MPH (and dl-MPH) may be underpinned by affinity and potential pharmacologic effects at NET and DAT sites, as well as sites relevant to serotonergic neurotransmission that may modulate mood, cognition, and motor behavior. However, the present exploratory studies reflect receptor binding affinities only. The specific pharmacological activities (i.e., agonism vs. antagonism) of these compounds await further exploration.

A double-blind, placebo-controlled trial of dexmethylphenidate hydrochloride and d,l-threo-methylphenidate hydrochloride in children with attention-deficit/hyperactivity disorder

OBJECTIVE

To evaluate the efficacy and safety of dexmethylphenidate hydrochloride (d-MPH, Focalin) for the treatment of attention-deficit/hyperactivity disorder (ADHD) and to test an a priori hypothesis that d-MPH would have a longer duration of action than d,l-threo-methylphenidate (d,l-MPH).

METHOD

This was a randomized, double-blind study conducted at 12 U.S. centers. One hundred thirty-two subjects received d-MPH (n=44), d,l-MPH (n=46), or placebo (n=42) twice daily for 4 weeks, with titration of the dose based on weekly clinic visits. The primary efficacy variable was change from baseline to last study visit on teacher-completed Swanson, Nolan, and Pelham Rating Scale (Teacher SNAP). Secondary efficacy measures included the change on parent-completed SNAP (Parent SNAP), Clinical Global Impressions Scale-Improvement (CGI-I) score, and Math Test performance. Assessments at home in late afternoon were included to test the hypothesis that d-MPH would have a longer duration of efficacy than d,l-MPH. Safety was assessed through monitoring occurrence and severity of adverse events and discontinuations related to them.

RESULTS

Treatment with either d-MPH (p=.0004) or d,l-MPH (p=.0042) significantly improved Teacher SNAP ratings compared with placebo. The d-MPH group showed significant improvements compared with placebo on the afternoon Parent SNAP ratings (p=.0003) and scores on the Math Test (p=.0236) obtained late in the afternoon at 6:00 p.m. Sixty-seven percent of patients showed improvement on d-MPH and 49% on d,l-MPH based on CGI-I scores. Both d-MPH and d,l-MPH were well tolerated, no patient in the d-MPH group and only two patients each in the d,l-MPH and placebo groups discontinued the study.

CONCLUSIONS

For the treatment of ADHD, an average titrated dose of 18.25 mg/day of d-MPH is as efficacious and safe as an average titrated dose of 32.14 mg/day of d,l-MPH. Both active treatments have large effect sizes. Thus, d-MPH and d,l-MPH appear to provide similar efficacy, and d-MPH may have longer duration of action after twice-daily dosing, but additional studies are needed to determine the statistical and clinical significance of this possibility.

Efficacy and safety of dexmethylphenidate extended-release capsules in children with attention-deficit/hyperactivity disorder

OBJECTIVE

The efficacy and safety of dexmethylphenidate extended release (d-MPH-ER) was compared to placebo in pediatric patients with attention-deficit/hyperactivity disorder (ADHD).

METHOD

This multicenter, randomized, double-blind, placebo-controlled, parallel-group, two-phase study included 97 patients (ages 6-17 years) with DSM-IV-defined ADHD. The study was carried out between 2001 and 2003. After a 2-week evaluation phase, patients were randomized to d-MPH-ER or placebo for 7 weeks. Flexible d-MPH-ER dosing (30 mg/day) was permitted for 5 weeks, then patients remained on their optimal dose during the last 2 study weeks. The primary efficacy measure was change from baseline to final rating in Conners ADHD/DSM-IV Scale-Teacher version (CADS-T) total subscale score. Secondary efficacy variables included changes from baseline to final visit in CADS-T Inattentive and Hyperactive-Impulsive subscale scores, CADS-P DSM-IV total subscale score and Inattentive and Hyperactive-Impulsive subscale scores, Clinical Global Impressions-Improvement (CGI-I) and CGI-Severity (CGI-S) scale scores, and Child Health Questionnaire Parent Form 50 scores.

RESULTS

d-MPH-ER improved CADS-T total scores significantly compared with placebo (p <.001), and 67.3% of d-MPH-ER patients were rated much improved or very much improved on CGI-I at final visit versus 13.3% of placebo patients (p <.001). More patients taking d-MPH-ER (49.1%) than placebo (25.5%) spontaneously reported adverse events suspected as drug related.

CONCLUSIONS

Once-daily d-MPH-ER was more effective than placebo in the treatment of ADHD in children and adolescents.

The use of a laboratory school protocol to evaluate concepts about efficacy and side effects of new formulations of stimulant medications

Recently, new long-acting formulations of racemic methylphenidate (MPH: Ritalin LA, Metadate CD and Concerta) and amphetamine (AMP: Adderall XR) were developed and are now approved by the Food and Drug Administration (FDA). In addition, dexmethylphenidate (Focalin), the pharmacologically active d-threo enantiomer of MPH, also was approved by the FDA. In the initial phases of development, prototypes of these five new formulations were evaluated using the University of California, Irvine (UCI) Laboratory School Protocol (LSP), in which surrogate measures of efficacy are collected in highly controlled settings rather than clinical measures of effectiveness in the less-controlled, natural environments of home or school. The LSP studies were followed by large effectiveness and safety studies required for gaining FDA approval. These initial efficacy and side effect studies in the LSP provided missing information about the basic pharmacokinetic (PK) and pharmacodynamic (PD) properties of MPH and AMP and produced some new discoveries (i.e., acute tolerance) that were used to help design the final products. The final once-a-day formulations used different drug delivery systems to achieve long-acting efficacy (Ritalin LA, Metadate CD, Concerta, Adderall XR). All four drug delivery systems were based on two processes: first, a bolus delivery (BD) process to achieve rapid onset of efficacy (mg), and second, a controlled delivery (CD) process to achieve rates of delivery (mg/hr) or a delayed bolus (mg) to maintain efficacy. A theoretical approach was used to compare and contrast the new once-a day formulations of MPH by selecting total daily doses (mg/d) that would equate drug delivery by the first process (mg of the initial bolus) and the second process (mg/hr over specified time period). In addition to efficacy, applications of the LSP to measure common side effects related to eating and sleeping were described and discussed.

A double-blind, placebo-controlled withdrawal trial of dexmethylphenidate hydrochloride in children with attention deficit hyperactivity disorder

OBJECTIVES

d,l-threo-methylphenidate HCl (D,L-MPH) is the most common treatment of attention deficit hyperactivity disorder (ADHD). A previous report showed placebo-controlled efficacy for the purified d-isomer (dexmethylphenidate hydrochloride, d-MPH, Focalin) with a 2:1 potency compared to dl, and suggested a 6-hour duration of action. This study complements that report by studying the effect of placebo-controlled discontinuation and retesting the duration of action.

METHODS

A 6-week, open-label titration of d-MPH (2.5-10 mg twice-a-day) was followed by a double-blind, placebo-controlled, 2-week withdrawal study of responders.

RESULTS

In the open titration, 82% of the 89 enrolled patients achieved a Clinical Global Impression-Improvement (CGI-I) rating of much or very much improved. Only 5 patients discontinued for adverse events. Seventy-five patients continued into the placebo-controlled discontinuation. For the randomly assigned d-MPH (n=35) and placebo (n=40) groups, mean ages, respectively, were 10.1 +/- 2.9 and 9.9 +/- 2.7 years, 86% and 78% were male, and 70.6% and 80.0% took the ceiling dose of 10 mg twice-daily, respectively. Each group had 80% combined type ADHD and 20% inattentive type. By the end of the 2-week, placebo-masked withdrawal, significantly more placebo patients (24 of 39) than d-MPH continuers (6 of 35) relapsed (61.5% versus 17.1%, p=0.001). Compared to d-MPH continuers, placebo patients deteriorated significantly more in the 2-week period on teacher ratings of the 18 ADHD symptoms rated 0-3 (p=0.028), the 3 p.m. and 6 p.m. parent ADHD symptom ratings (p=0.0026 and p=0.0381, respectively), and clinic (2-3 p.m.) and home (6 p.m.) Math Tests (p=0.024 and p<0.0001, respectively). The 6 p.m. scores replicated the significant effect at 6 hours reported in the previous study.

CONCLUSIONS

d-MPH is safe, tolerable, and effective, with a 6-hour duration of effect suggested by the significant difference from placebo at 6 hours on a double-blind discontinuation.

Efficacy and duration of effect of extended-release dexmethylphenidate versus placebo in schoolchildren with attention-deficit/hyperactivity disorder

OBJECTIVE

The aim of this study was to assess changes in symptomatology of attention-deficit/ hyperactivity disorder (ADHD) with extended-release dexmethylphenidate (d-MPHER) versus placebo in a laboratory classroom setting.

METHODS

This double-blind, placebo-controlled, crossover study randomized 54 children 6-12 years of age, stabilized on methylphenidate 20-40 mg/day. Patients participated in a practice day, then received 5 days of treatment with d-MPH-ER 20 mg/day or placebo. After a 1-day wash-out, they returned to the classroom and received 1 dose of their assigned treatment. Evaluations occurred predose and at postdose hours 1, 2, 4, 6, 8, 9, 10, 11, and 12. Children were then crossed over to the alternate treatment, using identical protocol. Primary efficacy variable was the Swanson, Kotkin, Agler, M-Flynn, and Pelham rating scale (SKAMP)-Combined scores, and primary analysis time point was 1 hour postdose; secondary efficacy variables over 12 hours included SKAMP-Attention and -Deportment scores and written math test results. Safety was assessed by adverse event (AE) recording following each period. Vital signs were recorded at each visit; laboratory tests were conducted at screening and final visit.

RESULTS

D-MPH-ER 20 mg/day showed a significant advantage over placebo as early as 1 hour postdose on SKAMP-Combined scores (p < 0.001). When analyzing the entire sample of 54 children, d-MPH-ER maintained significant superiority over placebo from hours 1 through 12 (p-values ranged from < 0.001 to 0.046). D-MPH-ER was well tolerated, with no severe AEs reported.

CONCLUSIONS

D-MPH-ER is safe and effective and improves classroom attention, deportment, and performance in children with ADHD.

Dexmethylphenidate

Dexmethylphenidate comprises only the d-enantiomer (the pharmacologically effective isomer) of racemic methylphenidate and is indicated for the treatment of patients aged > or =6 years with attention deficit hyperactivity disorder (ADHD). In a 4-week, double-blind trial in 132 children with ADHD, significantly greater improvements from baseline in teacher-rated Swanson, Nolan and Pelham (SNAP)-ADHD scores were seen in dexmethylphenidate and methylphenidate recipients, compared with placebo recipients. In addition, significantly more dexmethylphenidate and methylphenidate recipients, compared with placebo recipients, were much improved or very much improved according to Clinical Global Impression-Improvement of Illness scale scores. In the same study, parent-rated SNAP-ADHD scores had decreased by a significantly greater extent in dexmethylphenidate recipients at 3pm and 6pm and in methylphenidate recipients at 3pm, compared with placebo recipients. Significantly fewer dexmethylphenidate than placebo recipients failed treatment in a double-blind, treatment-withdrawal trial in 75 children with ADHD (17.1 vs 61.5%). In a noncomparative study in 22 children with ADHD, symptoms of ADHD, as assessed by teachers and parents, were controlled during the entire school day in 68 and 86% of dexmethylphenidate recipients, respectively, with a median duration of effect of 6.3 and 7.5 hours, respectively. Dexmethylphenidate was generally well tolerated in children with ADHD; adverse events were consistent with those known to be associated with agents containing methylphenidate.

D-methylphenidate and D,L-methylphenidate are not developmental toxicants in rats and rabbits

BACKGROUND

D,L-threo-Methylphenidate (D,L-MPH) is marketed currently for attention deficit hyperactivity disorder in children. D-threo-methylphenidate (dexmethylphenidate; D-MPH) is a refined formulation of D,L-methylphenidate containing only the active enantiomer and was recently approved in the U.S. for the same condition. D-Methylphenidate has been shown to be efficacious in patients at half the dose of D,L-MPH with a potentially improved therapeutic profile. The developmental toxicity of both compounds was determined and compared in rats and rabbits according to current International Conference on Harmonization (ICH) guidelines.

METHODS

Groups of pregnant rats were orally dosed twice daily 6 hr apart from Days 7 to 17 of presumed gestation (DG 7-17) for total daily doses of 2, 6 and 20 mg/kg D-MPH and 40 mg/kg D,L-MPH. Groups of presumed pregnant rabbits were similarly dosed from DG 6 to 18 for total daily doses of 4, 20 and 100 mg/kg D-MPH and 200 mg/kg D,L-MPH. Control groups for both studies were given water vehicle. Comprehensive clinical and developmental measurements were made. Satellite groups of animals were included in the main rat and rabbit studies for toxicokinetic assessment.

RESULTS

No drug-related mortality was seen in the F0 rats and rabbits. The number of rats with repetitive pawing, dilated pupil and aggression was significantly greater for the 40 mg/kg D,L-MPH compared to the 20 mg/kg D-MPH dosed rats. Maternal body weight and body weight gain were significantly reduced for both D-MPH and D,L-MPH groups compared to control. Maternal reproductive and litter parameters were unaffected by both drugs. No gross external, soft tissue, or skeletal alterations related to both compounds were seen in the fetuses. In rabbits, head-bobbing and hyperpnea were significantly greater for the 200 mg/kg D,L-MPH compared to 100 mg/kg D-MPH. No other maternal or fetal effects related to both compounds were seen. Exposure to D-MPH (as assessed by AUC) showed no teratogenic effects at exposures of up to 5.6 and 1.7 times for the rat and rabbit respectively compared to children taking the maximum therapeutic dose of 20 mg/day (10 mg twice a day). No teratogenic effects were seen for D,L-MPH in rat and rabbit at exposures of up to 3.7 to 11.7 times that of the maximum therapeutic pediatric dose of 60 mg/ day.

CONCLUSIONS

Rats and rabbits dosed with D,L-MPH exhibited significantly greater incidence of maternal clinical observations at twice the dose of D-MPH. Both D-MPH and D,L-MPH were not teratogenic in rats and rabbits at higher exposure levels compared to humans.

A randomized, double-blind, crossover study of once-daily dexmethylphenidate in children with attention-deficit hyperactivity disorder: rapid onset of effect

BACKGROUND

Long-acting methylphenidate formulations provide control of attention-deficit hyperactivity disorder (ADHD) symptoms for up to 12 hours; however, not all formulations have rapid onset of therapeutic effect, which is essential for providing symptom control during morning hours. The primary objective of this randomized, double-blind, crossover study was to assess the efficacy of dexmethylphenidate extended release (ER) versus placebo by measuring the change from pre-dose to 0.5 hours post-dose on the Swanson, Kotkin, Agler, M-Flynn and Pelham (SKAMP) rating scale.

METHODS

Eighty-six children (6-12 years) with ADHD diagnosed using the DSM-IV criteria were randomized to receive dexmethylphenidate ER 20 mg/day or placebo, sequentially, for 7 days, with the final dose administered in a laboratory classroom setting on day 7 of each treatment period. The primary efficacy comparison was change in the SKAMP-Combined score from pre-dose to 0.5 hours post-dose, with additional secondary assessments at 1, 2, 4, 6 and 8 hours post-dose. Secondary efficacy measures included change from pre-dose at all timepoints in the SKAMP-Attention and SKAMP-Deportment, Math Test-Attempted and Math Test-Correct scores, and change from baseline on the Conners' ADHD/DSM-IV Scale for Parents (CADS-P). In an exploratory analysis, a daily diary card was completed by parents on the children's in-home behaviour before school. Safety was assessed by occurrence of adverse events, monitoring of vital signs and interpretation of ECGs.

RESULTS

Significant improvements were noted at 0.5 hours and at all timepoints post-dose throughout the 8-hour laboratory classroom day for dexmethylphenidate ER vs placebo in the primary outcome measure of the SKAMP-Combined scores (p < 0.001), as well as SKAMP-Attention, SKAMP-Deportment, Math Test-Attempted and Math Test-Correct scores (p < 0.05). The changes from baseline in CADS-P scores were significantly greater with dexmethylphenidate ER than placebo (-16.382 vs -4.622; p < 0.001). Responses to all diary questions indicated significant improvement with dexmethylphenidate ER treatment versus placebo (all p < 0.001). The most common adverse events were abdominal pain (dexmethylphenidate ER 3.5%; placebo 4.7%), headache (dexmethylphenidate ER 3.5%; placebo 2.3%) and increased appetite (dexmethylphenidate ER 0%; placebo 3.5%).

CONCLUSION

Compared with placebo, once-daily dexmethylphenidate ER 20 mg provided rapid and significant improvement at 0.5 hours post-dose in attention, deportment and academic performance, which was sustained for 8 hours post-dose. Overall, once-daily dexmethylphenidate ER 20 mg was well tolerated. In an analysis of parental assessment of diary responses, children appeared more organized, and morning preparation for school was smoother and less frustrating with once-daily dexmethylphenidate ER compared with placebo.

D-Methylphenidate is non-genotoxic in in vitro and in vivo assays

D-Methylphenidate (dexmethylphenidate; D-MPH) and its racemate D,L-methylphenidate (D,L-MPH) are currently prescribed for the chronic treatment of attention deficit hyperactivity disorder (ADHD) in children. Studies have shown that D-MPH is the pharmacologically active enantiomer for ADHD and is therefore the preferred drug for the treatment of ADHD symptoms. Although studies on the mutagenicity of D,L-MPH have been conducted, similar data for D-MPH are lacking. Therefore, D-MPH was evaluated in the bacterial reverse mutation and mouse lymphoma assays with and without S9 and in a bone marrow micronucleus test in male and female CD-1 mice. As a comparison, the L-enantiomer and racemate were also included in the assessments. While MPH-associated toxicity was observed in the mammalian tests, none of the three compounds tested induced mutagenic or clastogenic effects. Our present results along with published epidemiological data from patient populations are consistent with the conclusion that D-MPH and D,L-MPH do not present a carcinogenic risk to humans.

Differential influences of ethanol on early exposure to racemic methylphenidate compared with dexmethylphenidate in humans

Enantioselective hydrolysis of oral racemic methylphenidate (dl-MPH) by carboxylesterase 1 (CES1) limits the absolute bioavailability of the pharmacologically active d-MPH isomer to approximately 30% and that of the inactive l-MPH to only 1-2%. Coadministration of dl-MPH with ethanol results in elevated d-MPH plasma concentrations accompanied by CES1-mediated enantioselective transesterification of l-MPH to l-ethylphenidate (EPH). The present study tested the hypothesis that administration of the pure isomer dexmethylphenidate (d-MPH) will overcome the influence of ethanol on d-MPH absorption by eliminating competitive CES1-mediated presystemic metabolism of l-MPH to l-EPH. Twenty-four healthy volunteers received dl-MPH (0.3 mg/kg) or d-MPH (0.15 mg/kg), with or without ethanol (0.6 g/kg). During the absorption phase of dl-MPH, concomitant ethanol significantly elevated d-MPH plasma concentrations (44-99%; P < 0.005). Furthermore, immediately following the ethanol drink the subjective effects of "high," "good," "like," "stimulated," and overall "effect" were significantly potentiated (P ≤ 0.01). Plasma l-EPH concentrations exceeded those of l-MPH. Ethanol combined with pure d-MPH did not elevate plasma d-MPH concentrations during the absorption phase, and the ethanol-induced potentiation of subjective effects was delayed relative to dl-MPH-ethanol. These findings are consistent with l-MPH competitively inhibiting presystemic CES1 metabolism of d-MPH. Ethanol increased the d-MPH area under the curve (AUC)(0-inf) by 21% following dl-MPH (P < 0.001) and 14% for d-MPH (P = 0.001). In men receiving d-MPH-ethanol, the d-MPH absorption partial AUC(0.5-2 hours) was 2.1 times greater and the time to maximum concentration (T(max)) occurred 1.1 hours earlier than in women, consistent with an increased rate of d-MPH absorption reducing hepatic extraction. More rapid absorption of d-MPH carries implications for increased abuse liability.

Neurobehavioral effects of racemic threo-methylphenidate and its D and L enantiomers in rats

D,L-methylphenidate (Ritalin) is used to treat attention deficit hyperactivity disorder (ADHD) in children. The therapeutic effect is predominantly due to the d enantiomer. Dexmethylphenidate (D-MPH; Focalin) was therefore developed for its better therapeutic index. The present study determined and compared the acute behavioral toxicity of D,L-MPH, D-MPH and L-MPH in rats after oral dosing. Comprehensive functional observational battery (FOB) evaluations and rota-rod tests were performed 30, 60 and 120 min after dosing. Ten rats/sex/dose were administered a single dose of vehicle, 2, 20, 100 mg/kg D,L-MPH and 1, 10, 50 mg/kg D-MPH or 1, 100, 500 mg/kg L-MPH. There was no mortality. Certain FOB evaluations were statistically significant from vehicle control at any of the time points with most occurring at 60 and 120 min in the high D,L-MPH dose. These included increases in rearing, difficulty in removal from box, arousal, click, tail-pinch and decreases in hind-limb splay distance, hind-limb grip strength and handling reactivity. Behavioral responses were also present at the mid-dose D,L-MPH and high dose D- and L-MPH. Responses in female were significantly different from males in D,L- and L-MPH groups suggesting a sex difference in sensitivity. In the rota-rod test, mean latency to remain on the rod was significantly less for males compared to control given high dose D-MPH and D,L-MPH. In females, latency times were significantly less for high doses of all three compounds. In summary, fewer significant FOBs were seen with D- and L-MPH compared to equimolar doses of D,L-MPH. L-MPH was the least potent in producing FOBs. These results were supported by rota-rod studies.

A Single-Dose, Two-Way Crossover, Bioequivalence Study of Dexmethylphenidate HCl with and without Food in Healthy Subjects

Attention deficit hyperactivity disorder (ADHD) in children is effectively treated by racemic oral methylphenidate (dl-MPH). The d-isomer (d-MPH) has been developed as an improved treatment for ADHD since only half the racemic dose is used. This study, performed in healthy subjects, assessed the effect of food on the pharmacokinetics of dexmethylphenidate hydrochloride (d-MPH HCl) in a single dose (2 x 10-mg tablets), two-way crossover with d-MPH administered to subjects in both a fasting state or after a high-fat breakfast. There were no serious or unexpected adverse events during the course of this study, with most events reported in comparable numbers of fed and fasted subjects. The bioequivalence of d-MPH was similar with or without food, with 90% confidence intervals of 88.2% to 104.6% and 105.9% to 118.2% for ln(C(max)) and ln[(AUC(0-infinity))], respectively. There was a marginal but statistically significant 1-hour increase in t(max) in the fed versus fasted state, reflecting an absorption delay. The rate of formation of the major metabolite, d-ritalinic acid (d-RA), was marginally decreased ( approximately 14%) after food. The extent of exposure to d-RA was similar (within 1.2%) between both treatments. There was a marginal but statistically significant difference in mean t(max) for d-RA between fed and fasted conditions, with peak concentration occurring 1.5 hours later after d-MPH administration with food. There was no measurable in vivo chiral inversion of d-MPH to l-MPH in plasma. In addition, the metabolism of d-MPH was stereospecific as d-MPH only produced d-RA. In summary, food had no substantial effect on the bioavailability of d-MPH, with an equivalent rate and extent of exposure obtained. Therefore, d-MPH can be administered without regard to food intake.

Open-label study of dexmethylphenidate hydrochloride in children and adolescents with attention deficit hyperactivity disorder

BACKGROUND

This pilot study examined the efficacy and duration of the effect of dexmethylphenidate (d-MPH) given once-daily in subjects with attention deficit hyperactivity disorder (ADHD).

METHOD

Subjects aged 6-18 years (inclusive) with ADHD were enrolled in this 8-week, openlabel study. Outcome measures included the Conners'Teacher and Parent Rating Scales, the Attention Deficit Disorder Rating Scale (ADDRS), the Clinical Global Impression (CGI) Scale, and teacher and parent visual analog scales to estimate the duration of efficacy. d-MPH was initiated at a dose of 2.5 mg/day. The dose was flexible, based on response and tolerability, and could be increased in increments of 2.5 mg/day to a maximum daily dose of 30 mg/day.

RESULTS

Twenty-two subjects (mean age, 8.7 +/- 0.4 years) were treated. Significant improvements (p <0.0001) from baseline occurred in the Conners' Teacher and Parent Rating Scales after 8 weeks. Of the evaluated subjects, 85.7% (18 of 21) showed at least a 30% improvement from baseline on the Conners' Teacher Rating Scale, and 86.4% (19 of 22) of subjects showed at least a 30% improvement from baseline on the Conners' Parent Rating Scale. Most subjects demonstrated an improvement on the ADDRS and the CGI-Improvement (CGI-I) scale. Median duration of effect was estimated at 6.2 hours (teachers) and at 7.5 hours (parents). On average, patients gained 2.4 pounds over the course of the study.

CONCLUSIONS

A single daily dose of d-MPH was effective in controlling ADHD in children and was well tolerated. Future studies are needed to confirm these findings and to evaluate chronic dosing with d-MPH.

Differential effects of amphetamine isomers on dopamine release in the rat striatum and nucleus accumbens core

RATIONALE

Current medications for attention-deficit/hyperactivity disorder (ADHD) include some single isomer compounds [dextroamphetamine (D: -amphetamine, dexedrine) and dexmethylphenidate (Focalin)] and some racemic compounds [methylphenidate and mixed-salts amphetamine (Adderall)]. Adderall, which contains approximately 25% L: -amphetamine, has been successfully marketed as a first-line medication for ADHD. Although different clinical effects have been observed for D: -amphetamine, Adderall, and benzedrine; potential psychopharmacological differences on the level of neurotransmission between D: -amphetamine and L: -amphetamine have not been well characterized.

OBJECTIVES

To evaluate potential differences in the isomers, we used the technique of high-speed chronoamperometry with Nafion-coated single carbon-fiber microelectrodes to measure amphetamine-induced release of dopamine (DA) in the striatum and nucleus accumbens core of anesthetized male Fischer 344 rats. Amphetamine solutions were locally applied by pressure ejection using micropipettes.

RESULTS

The presence of L: -amphetamine in the D: ,L: -amphetamine solutions did not cause increased release of DA but did change DA release kinetics. The D: ,L: -amphetamine-evoked signals exhibited significantly faster rise times and shorter signal decay times. This difference was also observed in the nucleus accumbens core. When L: -amphetamine was locally applied, DA release was not significantly different in amplitude, and it exhibited the same rapid kinetics of D: ,L: -amphetamine.

CONCLUSIONS

These data support the hypothesis that amphetamine isomers have different effects on release of DA from nerve endings. It is possible that L: -amphetamine may have unique actions on the DA transporter, which is required for the effects of amphetamine on DA release from nerve terminals.

A post hoc analysis of d-threo-methylphenidate hydrochloride (focalin) versus d,l-threo-methylphenidate hydrochloride (ritalin)

OBJECTIVE

To evaluate clinical measures of the benefit/risk ratio in a post hoc analysis of a clinical trial of d-threo-methylphenidate hydrochloride (d-MPH) and d,l-threo-methylphenidate hydrochloride (d,l-MPH).

METHOD

Data from a phase III clinical trial was used to compare equimolar doses of d-MPH and d,l-MPH treatment for attention-deficit/hyperactivity disorder (ADHD) on clinician ratings of improvement/deterioration, teacher ratings of remission, and duration of action.

RESULTS

d-MPH was clinically and statistically significantly superior to d,l-MPH on clinician's dimensional ratings of global improvement, teacher ratings of remission of ADHD symptoms and parent 6:00 p.m. ADHD symptom ratings. No treatment differences were observed for symptom ratings at 3:00 p.m. and for 6:00 p.m. math test performance.

CONCLUSION

The results suggest that the two drugs may have distinct profiles on the measures analyzed. Because d-MPH may have be more than twice the potency of d,l-MPH, the differences reported here are only applicable to the doses of the study drugs involved in the clinical trial. The results are limited by the exploratory nature of our analysis, small samples, and multiple analyses. The findings are suggestive that further study is warranted to look at these differences prospectively but cannot be used to draw clinical conclusions at this time.

Dexmethylphenidate extended-release capsules for attention deficit hyperactivity disorder

Medications for attention deficit hyperactivity disorder (ADHD) currently represent the ninth largest segment of the CNS market by sales, with 2.4 billion USD spent annually on this condition and 40% annual growth. Stimulant medications remain the most effective ADHD therapies and provide robust improvement in ADHD symptoms in both youth and adults. Current prescribing practices favor extended release preparations due to increased convenience, compliance and tolerability with once-daily dosing. Dexmethylphenidate extended release is a long-acting preparation of the ADHD medication Focalin (dexmethylphenidate immediate release) and was approved for marketing by the US Food and Drug administration in June 2005. Dexmethylphenidate consists of the single dextro-isomer form of d,l-methylphenidate commonly marketed as Ritalin. Dexmethylphenidate extended release utilizes spheroidal oral drug absorption system technology to achieve a 50% immediate medication delivery and 50% delayed release of dexmethylphenidate approximately 4 h after ingestion. Placebo-controlled, clinical trials in children and adults with ADHD have demonstrated efficacy for behavioral and academic ratings, with an analog classroom study showing medication effects up to 12 h after dosing. Dexmethylphenidate extended release was generally well tolerated with a side-effect profile similar to other stimulants. The most common reported side effects include diminished appetite and insomnia. Given its duration of effect, favorable tolerability and flexibility in dosing, dexmethylphenidate extended release is likely to gain considerable use as an ADHD treatment.

Dexmethylphenidate--Novartis/Celgene. Focalin, D-MPH, D-methylphenidate hydrochloride, D-methylphenidate, dexmethylphenidate, dexmethylphenidate hydrochloride

Celgene has developed a chirally pure form of methylphenidate (Ritalin), called dexmethylphenidate [d-methylphenidate, d-methylphenidate hydrochloride, d-MPH; Focalin]. The drug has been launched in the USA and is undergoing registration in Canada for the treatment of children with attention-deficit hyperactivity disorder (ADHD). Dexmethylphenidate is the single isomer version of racemic methylphenidate (Ritalin), which contains the active d isomer of Ritalin. Dexmethylphenidate acts via the inhibition of reuptake of norepinephrine and dopamine. Research is ongoing to further clarify the mode of therapeutic action in ADHD. Dexmethylphenidate was developed with the aim of reducing drug load, adverse events and drug interactions. Dexmethylphenidate provides effective management of attention-deficit hyperactivity disorder at half the dose of Ritalin. In April 2000, worldwide rights (excluding Canada) to dexmethylphenidate were granted to Novartis. Celgene has also granted Novartis rights to all related intellectual properties and patents. Novartis will fund all remaining development and marketing expenses required for regulatory approval and commercialisation of dexmethylphenidate. Crystaal Corporation, the marketing division of Biovail Corporation International, has exclusive Canadian marketing rights for all formulations of dexmethylphenidate. Novartis launched dexmethylphenidate (Focalin) in the USA during Q1 2002. It is available as a D-shaped tablet (2.5, 5 and 10 mg doses). Novartis had planned to use the tradename Ritadex, however the FDA recommended an alternative name due to potential prescribing errors with Ritalin. The finalized tradename to be used is Focalin. In July 2001, a new drug submission was filed with Canada's Therapeutic Products Programme for dexmethylphenidate in the treatment of attention-deficit disorder and attention-deficit hyperactivity disorder. Novartis is also developing an extended-release version of chirally pure dexmethylphenidate. Dexmethylphenidate has been found to be effective and well tolerated in clinical trials, involving a total of 684 children with ADHD and in 15 healthy adult volunteers. Dexmethylphenidate is a schedule II drug.

Dexmethylphenidate extended release: in attention-deficit hyperactivity disorder

Dexmethylphenidate extended release (XR) is an orally administered, bimodal release, capsule formulation of the active d-enantiomer of methylphenidate (MPH), which inhibits dopamine and norepinephrine (noradrenaline) reuptake to increase their concentration in the extraneuronal space. A single dose of dexmethylphenidate XR mimics the pharmacokinetic profile of two doses of dexmethylphenidate immediate-release formulation administered 4 hours apart, albeit with less fluctuation in plasma concentration. Once-daily dexmethylphenidate XR was more effective than placebo in reducing attention-deficit hyperactivity disorder (ADHD) symptom scores in children, adolescents and adults with ADHD in four randomised, double-blind, placebo-controlled trials of up to 7 weeks' duration. In crossover trials in children (aged 6-12 years), dexmethylphenidate XR 20 mg/day reduced mean ADHD symptom scores 1 hour after administration (by 43% in one trial) and was significantly better than placebo for up to 12 hours. Dexmethylphenidate XR 5-30 mg/day reduced mean ADHD symptom scores by 49%, while scores declined by 16% with placebo in a 7-week trial in children and adolescents (aged 6-17 years). Dexmethylphenidate XR 20, 30 or 40 mg/day reduced ADHD symptom scores by 36-46% versus a 21% reduction with placebo in a 5-week trial in adults (aged 18-60 years). Dexmethylphenidate XR was generally well tolerated in children, adolescents and adults with ADHD, with an adverse-event profile typical of MPH.

Dexmethylphenidate extended-release capsules for the treatment of attention deficit hyperactivity disorder

Dexmethylphenidate is a chirally pure d-isomer of the racemic mixture of methylphenidate. The extended-release form of this compound was developed using proprietary Spheroidal Oral Drug Absorption System technology. The product is approved for the treatment of attention deficit hyperactivity disorder in individuals as young as 6 years old. It represents the first methylphenidate product approved for use in adults. The agent's delivery system is designed to provide an initial release of medication immediately after dosing, with a second release approximately 4 h later. Blood levels first peak at approximately 1.5 h, and the second peak is noted at an average of 6.5 h post-dose. Laboratory classroom studies have demonstrated clinically and statistically meaningful efficacy throughout a 12-h day. Pharmacokinetics, safety and efficacy data are reviewed.