Pharmacology: Lipid Imbalances in ADHD:
Scientific evidence demonstrates that low levels of certain lipids are associated with Attention Deficit Hyperactivity Disorder (ADHD). While ADHD is a complex disorder, the etiology of which is multi-factorial, ADHD has been shown to be associated with metabolic disturbances such as lipid and glucose metabolism. The abnormalities in lipid metabolism that may occur in ADHD are associated with increased oxidative stress, higher rates of lipid degradation and decreased synthesis of phospholipids containing omega-3 fatty acids. Reduced levels of phosphatidylserine containing omega-3 fatty acids (PS-Omega-3) have implications in membrane structure and function, where they are believed to play an important role in signal transduction pathways, secretory vesicle release, and cell growth regulation.
Compared to healthy children of the same age, children with ADHD have lower blood levels of omega-3 long-chain polyunsaturated fatty acids (LC-PUFAs). These lipids, found also in the brain, play an essential role in brain development and function. In turn, it has been reported that omega-3 fatty acid deficiency is correlated to decreased brain phosphatidylserine, which is mainly in the form of PS-Omega-3.
PS-Omega-3 play an important role in the functioning of neuronal membranes, such as signal transduction, secretory vesicle release, cell-to-cell communication, and cell growth regulation. Thus, reduced levels of PS-Omega-3 and omega-3 may represent a complex lipid imbalance playing a role in the etiology/pathogenesis of ADHD.
Vayarin is a proprietary lipid composition of Phosphatidylserine-Omega-3 (PS-Omega-3), enriched with EPA. This form has been specially designed to deliver these essential lipids to the brain in order to support and maintain proper brain function.
Pharmacodynamics: Mechanism of Action:
Phosphatidylserine (PS) in the mammalian nervous system, which is characterized by relatively high levels of omega-3 fatty acids, has been implicated in numerous membrane related functions, such as maintaining the integrity of cell membranes, cell excitability and cell-to-cell recognition and communication. While the exact mechanism by which PS exerts its effects is not fully understood, PS has been found to regulate key proteins in neuronal membranes, including sodium/calcium ATPase and protein kinase C which undertake crucial functions in diverse signal transduction pathways. Similarly, PS interacts with Raf-1 protein kinase to promote a cascade of reactions that are believed to be involved in cell survival. Additionally, PS has been found to influence neurotransmitter activity, such as the release of acetylcholine, dopamine and noradrenaline and to increase brain glucose levels. Moreover, administration of a specially processed formulation consisting of PS conjugated to omega-3 fatty acids was found to significantly increase DHA levels in the brains of rats.
The Vayarin study was designed as a single-center randomized double blind placebo-controlled study of 15 weeks followed by an open label extension (OLE) of an additional 15 weeks. In the double-blind phase two hundred ADHD children (aged 6-13 years) were randomly assigned to receive Vayarin or placebo (four capsules a day). In order to evaluate the effect of a reduced dose, an OLE was conducted in 150 participants, assigned to consume two Vayarin capsules per day. The effect of Vayarin was assessed by rating scales and questionnaires, including the Conners' parent (CRS-P) and teacher (CRS-T) rating scales and the child health questionnaire (CHQ).
Following 15 weeks of Vayarin administration, significant improvement in both ADHD scores and quality of life were observed in the Vayarin group as compared to the placebo group, specifically in a subgroup of children with more pronounced hyperactive/impulsive behavior, as well as emotional dysregulation (see figure).
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See Table 1.
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Safety was evaluated by clinical laboratory measurements including biochemical and hematological parameters and by adverse events recording, physical examination and measurement of vital signs and weight. There were no clinically meaningful differences between treatment groups on the tested blood parameters in the double-blind study and within the treatment groups in the open-label extension. In addition, no significant findings were observed during physical examination or in vital signs or weight measurements in both study phases. Information regarding adverse events is elaborated in Adverse Reactions.
Pharmacokinetics: Absorption and Metabolism:
Phospholipids can break down to different levels or remain intact and be subsequently absorbed in the circulation and brain. Following dietary ingestion of PS, fatty acids esterified to the PS molecule can be hydrolyzed by pancreatic digestive enzymes, forming lyso-PS and free fatty acids. Once the lyso-PS is absorbed by the mucosal cells of the intestine, it can be reacylated into PS, while some of it may be converted into other phospholipids. PS and other phospholipids formed inside the enterocytes can either be transported in the lymphatic circulation as chylomicrons or in the portal circulation, and subsequently enter the general circulation for distribution to the body. Available evidence indicates that ingested PS reaches the systemic circulation and is incorporated into the phospholipid pool.
There are no known contraindications, however Vayarin could potentially interact with cholinergic and anticholinergic drugs. It is recommended to consult with a physician about Vayarin interactions that may apply to specific medical conditions.
The safety profile of PS conjugated to omega-3 (PS-Omega-3) is supported by several pre-clinical studies. Repeat-dose safety studies in rats and dogs showed that oral administration of PS-Omega-3 at doses up to 1000 mg/kg/day for up to 6 months was without any significant adverse effects of toxicological concern. The results of teratogenicity studies in rats at doses up to 200 mg/kg/day and in rabbits at doses up to 450 mg/kg/day showed that oral administration of PS-Omega-3 did not affect embryonic and fetal development. The mutagenic potential of PS-Omega-3 was investigated in several cell types and revealed no significant findings. In a micronucleus test, PS-Omega-3 was administered to mice at total dosages of 30, 150 and 300 mg/kg in two equal doses separated by 24-hours. The results of the study did not reveal any evidence of mutagenic potential or bone marrow toxicity.