Absence of cytogenetic effects in children and adults with attention-deficit/hyperactivity disorder treated with methylphenidate

In silico molecular docking and in vitro analysis of atomoxetine

Although atomoxetine, a selective norepinephrine reuptake inhibitor, is widely used in the treatment of attention-deficit/hyperactivity disorder (ADHD), there is limited data on its cytogenetic effects. This study aimed to investigate the cytotoxicity and genotoxicity of atomoxetine in vitro and silico. Chromosome aberration and micronucleus assays were used to analyze the genotoxic effect of atomoxetine in human peripheral blood lymphocytes under culture conditions. The mitotic index was assessed for cytotoxic potential. For the docking analysis, DNA receptor (1BNA) was prepared with ChimeraX, and the Atomoxetine molecule was optimized by Avogadro2.0 software. In silico molecular docking analysis was carried out utilizing SwissDock online platform. The results obtained were visualized using ChimeraX and Pymol software. Atomoxetine doses of 9.6 µg/mL (equal to about 1.2 mg/kg as a maintenance dose), 14.4 µg/mL (equal about to 1.8 mg/kg as the highest dose systematically tested), 48.0 µg/mL (equal about to 6 mg/kg as five times the maintenance dose) and 96.0 µg/mL (equal about to 12 mg/kg as ten times the maintenance dose) were analyzed. The findings clearly indicate that atomoxetine has no genotoxic effect at the therapeutic dose. However, we observed genotoxic effects at 48.0 and 96.0 µg/mL doses. No strong binding affinity occurs in silico analyses. As one of the initial inquiries into the in silico and in vitro appraisal of atomoxetine's genotoxic impacts, the research has established that atomoxetine does not significantly affect the frequency of chromosomal damage or micronucleus formation. Genotoxic effects should be kept in mind at doses above clinical practice.

The association between medication for attention-deficit/hyperactivity disorder and cancer

OBJECTIVE

A study on chromosomal abnormalities has raised concerns that medication with methylphenidate (MPH) for attention-deficit/hyperactivity disorders (ADHD) might increase the risk of cancer. We performed a rigorous test of the association between cancer and MPH and other drugs used for ADHD, based on data from nationwide Danish registers.

METHODS

Data were linked from five registers containing information on a total of 21,186 patients with ADHD, their drug prescription rates, and associated cancer diagnoses between 1994 and 2010. The cohort included subgroups treated with MPH only, amphetamines only, other ADHD-specific drugs only, antidepressants only, antipsychotics only, mixed medication, and a control group of patients with ADHD who had never taken medication. Frequencies of cancer diagnoses in these groups were compared. In addition, hazard risk (HR) ratios for developing cancer, and survival rates in these subgroups, were analyzed.

RESULTS

The mean observation time varied between 1.3 and 10.8 years for the various drugs. Cancer rates in the total group amounted to 1.27 per 10 000 person-years before and to 4.33 per 10 000 person-years after onset of treatment. The frequency of cancer was significantly higher (p = 0.05) after than before medication only in the antipsychotics subgroup. Furthermore, for mixed medication, the cancer frequency in a small subgroup was significantly higher (p < 0.05) after onset of medication than in the unmedicated subgroup. The Cox regression analysis indicated that none of the drugs represented risk factors, whereas higher dose (p < 0.001) and older age (p < 0.05) were risk factors for developing cancer.

CONCLUSIONS

The concern that children taking MPH and other drugs over long periods of time could be at a significant risk of developing cancer is not substantiated by these findings in a large and representative sample, which had been diagnosed and treated over a period of 17 years.

Long-term exposure to oral methylphenidate or dl-amphetamine mixture in peri-adolescent rhesus monkeys: effects on physiology, behavior, and dopamine system development

The stimulants methylphenidate and amphetamine are used to treat children with attention deficit/hyperactivity disorder over important developmental periods, prompting concerns regarding possible long-term health impact. This study assessed the effects of such a regimen in male, peri-adolescent rhesus monkeys on a variety of cognitive/behavioral, physiological, and in vivo neurochemical imaging parameters. Twice daily (0900 and 1200 hours), for a total of 18 months, juvenile male monkeys (8 per group) consumed either an unadulterated orange-flavored solution, a methylphenidate solution, or a dl-amphetamine mixture. Doses were titrated to reach blood/plasma levels comparable to therapeutic levels in children. [¹¹C]MPH and [¹¹C]raclopride dynamic PET scans were performed to image dopamine transporter and D₂-like receptors, respectively. Binding potential (BP(ND)), an index of tracer-specific binding, and amphetamine-induced changes in BP(ND) of [¹¹C]raclopride were estimated by kinetic modeling. There were no consistent differences among groups on the vast majority of measures, including cognitive (psychomotor speed, timing, inhibitory control, cognitive flexibility), general activity, physiological (body weight, head circumference, crown-to-rump length), and neurochemical (ie, developmental changes in dopamine transporter, dopamine D₂ receptor density, and amphetamine-stimulated dopamine release were as expected). Cytogenetic studies indicated that neither drug was a clastogen in rhesus monkeys. Thus, methylphenidate and amphetamine at therapeutic blood/plasma levels during peri-adolescence in non-human primates have little effect on physiological or behavioral/cognitive development.

The genetic toxicity of methylphenidate: a review of the current literature

Attention deficit/hyperactivity disorder (ADHD), a common children's behavioral disorder, is characterized by inattention, hyperactivity and impulsivity. The disorder is thought to stem from abnormalities in the catecholamine pathway and the symptoms of the disorder have been successfully treated with methylphenidate (MPH) since the FDA approved the drug in the 1950s. MPH underwent the appropriate safety testing as part of the FDA approval process; however, a publication in 2005 that reported significant increases in cytogenetic damage in the lymphocytes of MPH-treated pediatric patients caused concern for patients and their families, the pharmaceutical industry and regulatory agencies. This communication will review the many studies that were subsequently initiated worldwide to address the genetic safety of MPH in both animal models and human subjects. Animal experiments broadened the study protocols used in the 2005 investigation to include a wider dose-range, a longer treatment period and automated scoring of biological endpoints, where possible, to reduce observer bias. The human subject studies replicated the experimental design used in the 2005 study, but increased the treatment periods and the sizes of the study populations. Neither the laboratory animal nor human subject studies found an increase in any of the measures of genetic damage that were evaluated. Taken together, these new studies are consistent with the original safety evaluation of the FDA and do not support the hypothesis that MPH treatment increases the risk of genetic damage in ADHD patients. Published 2012. This article is a US Government work and is in the public domain in the USA.

Methylphenidate lacks genotoxic effects in mouse peripheral blood erythrocytes

Methylphenidate (MPH; Ritalin®; Novartis Pharmaceuticals, Inc., Basel, Switzerland) has been prescribed to treat attention deficit/hyperactivity disorder (ADHD) since its approval by the U.S. Food and Drug Administration over 50 years ago. Due to concerns that MPH might induce cytogenetic alterations in children, treatment with this drug has been a controversial issue. In the present study, we assessed the frequency of micronucleated erythrocytes (MNEs), micronucleated polychromatic erythrocytes (MNPCEs), and polychromatic erythrocytes (PCEs) in peripheral blood samples from mice treated with three different doses of MPH (30, 60, or 125 mg/kg). We found no evidence of increased MNEs or MNPCEs, nor did PCEs decline. These results add to the accumulating evidence that MPH does not induce genotoxic or cytotoxic damage.

Advances in understanding and treating ADHD

Attention deficit hyperactivity disorder (ADHD) is a neurocognitive behavioral developmental disorder most commonly seen in childhood and adolescence, which often extends to the adult years. Relative to a decade ago, there has been extensive research into understanding the factors underlying ADHD, leading to far more treatment options available for both adolescents and adults with this disorder. Novel stimulant formulations have made it possible to tailor treatment to the duration of efficacy required by patients, and to help mitigate the potential for abuse, misuse and diversion. Several new non-stimulant options have also emerged in the past few years. Among these, cognitive behavioral interventions have proven popular in the treatment of adult ADHD, especially within the adult population who cannot or will not use medications, along with the many medication-treated patients who continue to show residual disability.