Lisdexamfetamine



Lisdexamfetamine dimesylate ( L -lysine-dextroamphetamine dimesylate) is a psychostimulant prodrug of the phenethylamine and amphetamine chemical classes. Its molecular structure consists of dextroamphetamine coupled with the essential amino acid L -lysine. Lisdexamfetamine itself is inactive and acts as a prodrug to dextroamphetamine upon cleavage of the lysine portion of the molecule.

Lisdexamfetamine can be prescribed for the treatment of attention deficit hyperactivity disorder (ADHD) in children six to twelve years and in adults as a part of a treatment program that may include other measures (i.e., psychological, educational, social). The safety and the efficacy of lisdexamfetamine dimesylate in people three to five years old have not been established. Lisdexamfetamine is also being investigated for possible treatment of major depressive disorder, cognitive impairment associated with schizophrenia, excessive daytime sleepiness, and binge eating disorder.

In the United States lisdexamfetamine is a Schedule II controlled substance (DEA number 1205) and the aggregate production quota for 2014 is 23,750 kilograms of anhydrous acid or base.

In the United Kingdom, Denmark, Sweden, Germany, Finland, Spain and Norway lisdexamfetamine is available and licensed under the brand name Elvanse (Tyvense in Ireland) and is available in 30 mg, 50 mg and 70 mg capsules. It was recently scheduled as a Schedule 2/Class B substance in the United Kingdom, allowing for its medical use but placing strict criminal penalties for its unauthorised production, supply, possession etc.

Lisdexamfetamine is currently in Phase II trials in Japan for ADHD, as well as under investigation for the treatment of binge eating disorder.

Medical
Individuals over the age of 65 were not commonly tested in clinical trials of lisdexamfetamine. Therefore, there is insufficient data to determine how older individuals respond. People over the age of 65 should start on the low end of dosing schedules due to the prevalence of decreased hepatic function, decreased renal function, and comorbidities in this population.

Contraindications
Pharmaceutical lisdexamfetamine dimesylate is contraindicated in patients with hypersensitivity to amphetamine or any other ingredients that it contains. It is also contraindicated in in patients who have used a monoamine oxidase inhibitor (MAOI) within the last 14 days. Amphetamine products are contraindicated by the United States Food and Drug Administration (USFDA) in people with a history of drug abuse, heart disease, or severe agitation or anxiety, or in those currently experiencing arteriosclerosis, glaucoma, hyperthyroidism, or severe hypertension. The USFDA advises anyone with bipolar disorder, depression, elevated blood pressure, liver or kidney problems, mania, psychosis, Raynaud's phenomenon, seizures, thyroid problems, tics, or Tourette syndrome to monitor their symptoms while taking amphetamine. Amphetamine is classified in US pregnancy category C. This means that detriments to the fetus have been observed in animal studies and adequate human studies have not been conducted; amphetamine may still be prescribed to pregnant women if the potential benefits outweigh the risks. Amphetamine has also been shown to pass into breast milk, so the USFDA advises mothers to avoid breastfeeding when using it. Due to the potential for stunted growth, the USFDA advises monitoring the height and weight of children and adolescents prescribed amphetamines. Prescribing information approved by the Australian Therapeutic Goods Administration further contraindicates anorexia.

Availability
Lisdexamfetamine dimesylate is a white to off-white powder that is soluble in water (792 mg/mL). Vyvanse capsules contain 20 mg, 30 mg, 40 mg, 50 mg, 60 mg, and 70 mg of lisdexamfetamine dimesylate and the following inactive ingredients: microcrystalline cellulose, croscarmellose sodium, and magnesium stearate. The capsule shells contain gelatin, titanium dioxide, and one or more of the following: FD&C Red #3, FD&C Yellow #6, FD&C Blue #1, Black Iron Oxide, and Yellow Iron Oxide.

Side effects
Products containing lisdexamfetamine have a side effect profile comparable to those containing amphetamine.

Interactions

 * Acidifying Agents: Drugs that acidify the urine, such as ascorbic acid, increase urinary excretion of amphetamines thus decreasing the half-life time of lisdexamfetamine in the body.


 * Alkalinizing Agents: Drugs that alkalinize the urine, such as sodium bicarbonate, decrease urinary excretion of amphetamines thus increasing the half-life time of lisdexamfetamine in the body.


 * Monoamine Oxidase Inhibitors: Concomitant use of MAOIs and central nervous system stimulants such as lisdexamfetamine can cause hypertensive crisis.

Mechanism of action
Lisdexamfetamine is an inactive prodrug that is converted in the body to dextroamphetamine, a pharmacologically active compound which is responsible for the drug’s activity. After oral ingestion, lisdexamfetamine is broken down by enzymes in red blood cells to form L -lysine, a naturally occurring essential amino acid, and dextroamphetamine. The conversion of lisdexamfetamine to dextroamphetamine is not affected by gastrointestinal pH and is unlikely to be affected by alterations in normal gastrointestinal transit times.

The optical isomers of amphetamine, i.e., dextroamphetamine and levoamphetamine, are TAAR1 agonists and vesicular monoamine transporter 2 inhibitors that can enter monoamine neurons; this allows them to release monoamine neurotransmitters (dopamine, norepinephrine, and serotonin, among others) from their storage sites and the presynaptic neuron, as well as prevent the reuptake of these neurotransmitters from the synaptic cleft.

Lisdexamfetamine was developed with the goal of providing a long duration of effect that is consistent throughout the day, with reduced potential for abuse. The attachment of the amino acid lysine slows down the relative amount of dextroamphetamine available to the blood stream. Because no free dextroamphetamine is present in lisdexamfetamine capsules, dextroamphetamine does not become available through mechanical manipulation, such as crushing or simple extraction. A relatively sophisticated biochemical process is needed to produce dextroamphetamine from lisdexamfetamine. As opposed to Adderall, which contains roughly equal parts of racemic amphetamine and dextroamphetamic salts, lisdexamfetamine is a single-enantiomer dextroamphetamine formula. Studies conducted show that lisdexamfetamine dimesylate may have less abuse potential than dextroamphetamine and an abuse profile similar to diethylpropion at dosages that are FDA-approved for treatment of ADHD, but still has a high abuse potential when this dosage is exceeded by over 100%.

History, society, and culture
Lisdexamfetamine was developed by New River Pharmaceuticals, who were bought by Shire Pharmaceuticals shortly before lisdexamfetamine began being marketed. It was developed for the intention of creating a longer-lasting and less-easily abused version of dextroamphetamine, as the requirement of conversion into dextroamphetamine via enzymes in the red blood cells increases its duration of action, regardless of the route of ingestion. The drug lisdexamfetamine dimesylate is the first prodrug of its kind.

On April 23, 2008, Vyvanse received FDA approval for the adult population. In a randomized, double-blind, four-week phase III trial in adult patients with ADHD, dosages of 30, 50 or 70 mg/day of oral lisdexamfetamine caused a significantly greater improvement in ADHD-Rating Scale total score than placebo. On February 19, 2009, Health Canada approved 30 mg and 50 mg capsules of lisdexamfetamine for treatment of ADHD. On February 8, 2012, Vyvanse received FDA approval for maintenance treatment of adult ADHD. In February 2014, Shire announced that two late-stage clinical trials had shown that Vyvanse was not an effective treatment for depression.

Brand names
Lisdexamfetamine is sold as Tyvense (IE), Elvanse (UK) , Venvanse (BR) , Vyvanse (CA, US).