Module 3: Drugs that Influence the CNS Flashcards
What is the main excitatory neurotransmitter in the brain?
Glutamate
What is the main inhibitory neurotransmitter in the brain?
Gamma-aminobutyric acid (GABA)
How do drugs increase the GABA inhibitory signalling in the brain?
The drugs mimic the inhibitory effects of GABA by binding onto the chloride channel, slowing excitatory CNS transmission
What is the definition of Drug Classes?
A class of drugs is a group of drugs that have the same mechanism of action and similar pharmacological properties
T/F Each class of sedative-hypnotic agents bind to a different site on the chloride channel
True!
What are the three main classes of sedative-hypnotic drugs that bind to the chloride ion channel?
Benzodiazepines, barbiturates, the “Z” drugs
What are the three classes of barbiturates?
Long acting (1-2 days)
Short acting (3-8 hours)
Ultrashort acting (20 minutes)
What receptor do benzodiazepines bind of the chloride ion channel? What happens when it binds?
The benzodiazepine receptor. Upon binding, benzodiazepines increase the frequency of the opening of the chloride channel, enhancing GABA’s effect
What are some of the pharmacological properties of Benzodiazepines?
High therapeutic index, relieve anxiety, produce sedation, decrease aggression, minimal suppression of REM sleep, skeletal muscle relaxation
How do benzodiazepines negatively effect pregnant/breastfeeding individuals?
Benzodiazepine freely crosses the placenta and distributes to the fetus. In the first trimester, can cause fetal abnormalities. Also transfers through the milk, which can expose infants to doses, leading to sedation or death
Which of the GABA modifying drugs are used to treat insomnia? Why?
The “Z” drugs and short-acting benzodiazepines; The depressive nature makes users feel drowsy
Describe the pharmacology of barbiturates
- Low therapeutic index
- Suppress REM type sleep
- Lethality is common when combined with alcohol
- No antidote
- Death can occur from withdrawl
Why do benzodiazepines have a high misuse potential?
They are wildly prescribed and are often used with other CNS depressants (alcohol) or stimulants
Describe the clinical use of barbiturates
Ultrashort and short acting can be used to induce anesthesia.
Long acting have been used as anti-seizure medications
Limited clinical use
How do benzodiazepines work?
They bind to the chloride channel at the barbiturate receptor, and act as an allosteric activator, increasing the duration of the opening of the chloride channel, increasing GABA effects
How do benzodiazepines negatively effect the elderly?
Can produce cognitive dysfunction. Due to slower metabolism, are more likely to experience over-sedation and falls
Why do barbiturates have a high misuse potential?
They have quite a bit of pleasurable effects, tolerance is rapidly made
T/F Benzodiazepines are first line of treatment for anxiety? Explain.
False. They are second-line due to their potential for over-sedation, cognitive impairment, and psychomotor incoordination
Which of the GABA modifying drugs are used to treat anxiety?
Benzodiazepines
Which of the GABA modifying drugs are used to treat seizures?
Long acting barbiturates for partial seizures, benzodiazepines for status epilepticus
Which of the GABA modifying drugs are used to treat skeletal muscle spasm (e.g., cerebral palsy). Why?
Benzodiazepines; relax the muscles
Which of the GABA modifying drugs are used to treat alcohol withdrawl syndrome? Why?
Benzodiazepines; have cross tolerance with alcohol
What are generalized seizures?
Involve the entire CNS, accompanied by loss of consciousness. Subdivided based on the type of movement and duration of loss of consciousness that occurs during the seizure
What are the three ways anti-seizure drugs decrease glutamate-induced excitation?
Increasing the inhibitory input (GABA)
Blocking electrical activity of the nerve to slow nerve impulses (blocking sodium channel activity)
Decreasing excitatory transmission (decreasing the release of glutamate at the synapse)
What are partial (focal) seizures?
Involve focal areas of the brain and have more restricted symptoms. May involve motor disturbances, as well as alterations of perceptions or behaviour
What are some of the adverse effects of anticonvulsants?
Sedation, tremor, cognitive impairment, nausea, vomiting, diarrhea, elevated hepatic enzymes, skin rashes
How are adverse effects of anticonvulsants minimzied?
By starting with a low dose and slowly increasing; administering with meals
T/F Most anticonvulsants reduce biotransformation enzymes
False! They induce biotransformation enzymes - so the metabolism of concurrently administered drugs is also increased
What are the three types of depression?
Reactive (secondary) depression
Major depression
Depression associated with dipolar disorder
What are the three theories surrounding the cause of major depression? Give a brief description
The amine hypothesis
Neurotrophic hypothesis
Neuroendocrine hypothesis
Give a brief description of the amine hypotheisis
Suggests that depression is the result of a deficiency of the excitatory neurotransmitters in the CNS (norepinephrine, serotonin, and dopamine)