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Drug withdrawal includes a variety of negative symptoms experienced when drug use is discontinued. These symptoms usually are opposite of the effects of the drug. For example, withdrawal from sedative drugs often produces unpleasant arousal and agitation. In addition to withdrawal, many individuals who are diagnosed with substance use disorders will also develop tolerance to these substances. Psychological dependence, or drug craving, is a recent addition to the diagnostic criteria for substance use disorder in DSM-5. This is an important factor because we can develop tolerance and experience withdrawal from any number of drugs that we do not abuse. In other words, physical dependence in and of itself is of limited utility in determining whether or not someone has a substance use disorder.

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The effects of all psychoactive drugs occur through their interactions with our endogenous neurotransmitter systems. Many of these drugs, and their relationships, are shown in Table 4.2. As you have learned, drugs can act as agonists or antagonists of a given neurotransmitter system. An agonist facilitates the activity of a neurotransmitter system, and antagonists impede neurotransmitter activity.

Drugs and Their Effects

Class of Drug Examples Effects on the Body

Effects When Used Psychologically Addicting?

Stimulants Cocaine, amphetamines (including some ADHD medications such as Adderall), methamphetamines, MDMA (“Ecstasy” or “Molly”)

Increased heart rate, blood pressure, body temperature

Increased alertness, mild euphoria, decreased appetite in low doses. High doses increase agitation, paranoia, can cause hallucinations. Some can cause heightened sensitivity to physical stimuli. High doses of MDMA can cause brain toxicity and death.

Yes

Sedative- Hypnotics (“Depressants”)

Alcohol, barbiturates (e.g., secobarbital, pentobarbital), Benzodiazepines (e.g., Xanax)

Decreased heart rate, blood pressure

Low doses increase relaxation, decrease inhibitions. High doses can induce sleep, cause motor disturbance, memory loss, decreased respiratory function, and death.

Yes

Chapter 4 | States of Consciousness 135

 

 

Drugs and Their Effects

Class of Drug Examples Effects on the Body

Effects When Used Psychologically Addicting?

Opiates Opium, Heroin, Fentanyl, Morphine, Oxycodone, Vicoden, methadone, and other prescription pain relievers

Decreased pain, pupil dilation, decreased gut motility, decreased respiratory function

Pain relief, euphoria, sleepiness. High doses can cause death due to respiratory depression.

Yes

Hallucinogens Marijuana, LSD, Peyote, mescaline, DMT, dissociative anesthetics including ketamine and PCP

Increased heart rate and blood pressure that may dissipate over time

Mild to intense perceptual changes with high variability in effects based on strain, method of ingestion, and individual differences

Yes

Table 4.2

Alcohol and Other Depressants

Ethanol, which we commonly refer to as alcohol, is in a class of psychoactive drugs known as depressants (Figure 4.15). A depressant is a drug that tends to suppress central nervous system activity. Other depressants include barbiturates and benzodiazepines. These drugs share in common their ability to serve as agonists of the gamma-Aminobutyric acid (GABA) neurotransmitter system. Because GABA has a quieting effect on the brain, GABA agonists also have a quieting effect; these types of drugs are often prescribed to treat both anxiety and insomnia.

136 Chapter 4 | States of Consciousness

This OpenStax book is available for free at http://cnx.org/content/col31502/1.4

 

 

Figure 4.15 The GABA-gated chloride (Cl–) channel is embedded in the cell membrane of certain neurons. The channel has multiple receptor sites where alcohol, barbiturates, and benzodiazepines bind to exert their effects. The binding of these molecules opens the chloride channel, allowing negatively-charged chloride ions (Cl–) into the neuron’s cell body. Changing its charge in a negative direction pushes the neuron away from firing; thus, activating a GABA neuron has a quieting effect on the brain.

Acute alcohol administration results in a variety of changes to consciousness. At rather low doses, alcohol use is associated with feelings of euphoria. As the dose increases, people report feeling sedated. Generally, alcohol is associated with decreases in reaction time and visual acuity, lowered levels of alertness, and reduction in behavioral control. With excessive alcohol use, a person might experience a complete loss of consciousness and/or difficulty remembering events that occurred during a period of intoxication (McKim & Hancock, 2013). In addition, if a pregnant woman consumes alcohol, her infant may be born with a cluster of birth defects and symptoms collectively called fetal alcohol spectrum disorder (FASD) or fetal alcohol syndrome (FAS).

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