Methamphetamine is a particular compound of Amphetamine. Regular amphetamines are psycho-stimulants with similar effects to that of caffeine, though not as mild. Methamphetamine is a synthesized drug that is the most potent of amphetamines (Grilly, 2001). This is because a methamphetamine molecule is a molecule with methyl group added to the structure. This methyl group allows the drug to pass quicker through the blood brain barrier (Hart & Ksir, 2011). When one discusses Methamphetamine potency, one is referring to the dose or concentration at which a substance reaches half of its maximal efficacy.
Efficacy is the amount of activation once a substance is bound to the receptor it has affinity (or ability to remain bound). The maximal efficacy, therefore, is reached when increasing the dosage of a drug will no longer produce a greater activation of receptors. If one says that Methamphetamine is the most potent of Amphetamine combinations, one is stating that a dose of Methamphetamine will have a quicker activation (efficacy) rate at a lower dose than other combinations. In order for potency and efficacy to happen, a receptor must be present to be activated.
While the stimulant actions of methamphetamine are generally thought to involve dopamine systems (Fleckenstein et al. , 2000), it has been known for many years that methamphetamine also binds to sigma receptors Sigma receptors are present in organ systems that mediate the actions of methamphetamine (e. g. brain, heart, lung). In addition, activation of these receptors stimulates dopamine synthesis and release (Basianetto et al. , 1995). The major neurotransmitters that have an increase in activity after indulging in the drug are: dopamine, norepinephrine, and serotonin.
Methamphetamines wax the activity of these neurotransmitters b stimulating release rather than inhibiting reuptake (Hart & Ksir, 2011). Part of the euphoric feelings associate with methamphetamines is that amphetamine heightens dopamine levels in the nucleaus accumbens brain region that is important for drug-related reinforcement (Tenayuca JM. & Nazarian A. , 2012). Focusing on dopamine, however, is an oversimplisitc view. As it seems that norephinephrine mediates the euphoric effect of amphetamines.
Scientists discovered this when they realized that dopamine antagonists do not block the euphoria produced, as one would expect an antagonist to do (Brauer, L. H. , & H. deWit, 1997). Methamphetamine increases alertness, concentration, energy, and in high doses, can induce euphoria, enhance self-esteem and increase libido (Mack et al. , 2005). It can also have adverse feeling physiological effects: repetitive and obsessive behaviors and paranoia (Dart, 2004).
A study performed on female Japanese prison inmates suffering from methamphetamine addiction showed 20% experienced a psychosis resembling schizophrenia which persisted for longer than six months post-methamphetamine use (Barr et al. , 2006). In an Australian study of 309 active amphetamine users, 18% had experienced a clinical level psychosis in the past year (McKetin et al. , 2006).
This is a phenomenon known as “stimulant psychosis,” this generally occurs in abusers who take high doses of the stimulant, but, rarely, can affect people who take stimulants under medical supervision (for conditions such as: asthma, ADHD or obesity) (Curran et al. ,2004). Pharmacokinetics Following oral administration, methamphetamine is readily absorbed into the bloodstream. Methamphetamine’s high lipophilicity also allows it to cross the blood brain barrier quickly.
The amphetamine metabolite peaks at 10 to 24 hours. Methamphetamine is also well absorbed following inhalation and following snorting (Schep et al. , 2010). There are some reports of the meth community taking the drug by suppository. This would make for the second fastest route of administration after intravenous. The fastest peak effect of 5-10 minutes occurs when the drug is smoked (Mundy, 2001).
Methamphetamine is metabolized in the liver (Schep et al. , 2010), and is excreted by the kidneys (Greenhill et al. , 2003). The half-life of methamphetamine is variable with a mean value of between 9 and 12 hours.
The drug is completely eliminated within two days. (Schep et al. , 2010). Mechanism of Tolerance and Dependence Withdrawal As a result of methamphetamine-induced neurotoxicity to dopaminergic neurons, chronic abuse may also lead to post-withdrawal syndrome, which persists beyond the withdrawal period for months, and even up to a year. In addition to psychological harm, physical harm – primarily consisting of cardiovascular damage – may occur with chronic use or acute overdose. References: Bastianetto S, Rouquier L, Perrault G, Sanger DJ. (1995).
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