The two main forms of memory are declarative memory and procedural memory. Declarative memory is memory of past events and facts, whereas procedural memory is memory of how to carry out routine-based tasks, such as the memory of how to ride a bike. The type of memory most easily affected by recreational and prescription drugs is short-term declarative memory. The side-effects of prescription drugs tend to be reversible, but continued use of drugs that impair cognitive ability may, in some cases, lead to permanent damage.
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Anti-anxiety medications in the benzodiazepine class may cause short-term memory loss. The benzodiazepines most commonly prescribed for anxiety are alprazolam and diazepam. Alprazolam, which is sold under the brand name Xanax, was initially developed as a sleep medication but is now primarily prescribed for its axiolytic effects. Diazepam, which is sold under the brand name Valium, is a muscle relaxant primarily prescribed as an anticonvulsant and anti-anxiety drug. Because the benzodiazepines enhance the effects of the brain inhibitory neurotransmitter GABA, drugs in this class slow down neurological functions, including memory functions, reports a research team in the March 2002 issue of "Consciousness and Cognition."
Sleeping pills in the imidazopyridines class include zolpidem, zopiclone, and zalepon. Like benzodiazepines, imidazopyridines bind to the GABA receptor. The mechanism of action is different but the end result is the same. They enhance the action of the inhibitory chemical GABA, thereby slowing down brain functions. Zolpidem, which is sold under the brand name Ambien, is the most commonly prescribed drug in this class. This sleeping pill can result in severe amnesia, sleep-eating and other zombie-like behavior, reports a study in the October 2007 issue of "Journal of Clinical Sleep Medicine."
Anesthesia-inducing drugs include barbiturates, etomidate, propofol and ketamine. In large doses, these drugs cause unconsciousness. Some of them also relieve pain. The drugs are primarily used in general anesthesia, capital punishment and active euthanasia. At lower doses, they act as sedatives. Like benzodiazepines and imidazopyridines, most anesthesia-inducing drugs enhance the retarding effects of the GABA neurotransmitter. Others bind to the excitatory NMDA receptor without stimulating it, thus slowing down the transfer of neuron signals. Both kinds of inhibitory action can cause cognitive retardation, according to a review published in the October 2002 issue of "Nature Neuroscience."
Statins inhibit the synthesis of low-density lipoprotein, LDL, cholesterol and increase the uptake of LDL cholesterol from the bloodstream. At high blood concentrations, LDL cholesterol can cause narrowing of the blood vessels, strokes and heart attacks. Researchers disagree about whether statins help relieve memory loss or are a trigger for it, reports a review article published in the March 2008 issue of "Neurology Today." Constrictions of blood vessels in the brain can cause cognitive problems. But some case studies indicate that statins may speed up the progression of dementia.
Street drugs are typically impure forms of sedative or excitatory agents. Impure drugs may contain additive drugs that can impair cognitive functions. In addition to the potential side-effects of the additive components, the active ingredients themselves can trigger memory loss and other cognitive problems. Sedatives in the classes describe above and opioids, such as heroin, morphine and codeine, cause a retardation of the neurological system. Long-term use of stimulants, such as amphetamines, cocaine and Ecstasy, which raise the brain's levels of dopamine, serotonin and norepinephrine, causes cognitive impairment due to tolerance, reports a research team in the February 2010 issue of "Journal of Psychopharmacology."