CNS Stimulants Flashcards
What are the three ways sympathomimetic stimulants can work?
- increase release of NE and DA
- Block NE and DA reuptake
- Inhibit MAO
What affects will sympathomimetrics have on respiration?
they will stimulate the medullary respiratory center and increase rate and depth
What are the acute side effects of sympathomimetics?
basically exaggerated therapeutic effects:
headaches, arrhythmias, palpitations, anginal pain, hyperthermia, dizziness, agitation, confusion, insomnia, seizures and coma
How do you treat an acute sympathetomimetic toxicity?
give an antipsychotic
acidify the patient’s urine
What toxicity can develop with chromic amphetamine use?
amphtemine psychosis:
vivid hallucinations, paranoid delusions and compulsions
marked weight loss
How long does it take for an amphetamine psychosis to resolve once you stop the drug?
7-10 days
What will abrupt withdrawal of a sympathetomimetic cause?
craving for the drug, prolonged sleep, general fatigue, excessive eating and depression
What are the 5 things we use sympathomimetics for?
ADHD
Narcolepsy
Chronic Fatigue
Weight loss
analeptic to reverse drug-induced depression (but we don’t do that anymore really)
How is cocaine usually administered?
- crystalline form (in hydrochloride salt) can be snorted
- crystals can be dissolved and the base can be extracted with ether to then smoke
- IV injection
- indigenous populations chew the leaves and swallow saliva
What is the potency of cocaine compared to amphetamine?
1 mg cocaine = 10 mg amphetamine
What specific actions of cocaine causes the motor effects? The euphoria effects?
motor effects are from the blocked reuptake of NE
euphoria is from the blocked reuptake of dopamine
How is MDMA derived from methamphetamine and why does it reach the brain more rapidly?
it has an addition of a methyl groups
this increases the lipophilicity, so it gains rapid entry into the brain
What method of action does MDMA have that the amphetmaines dont?
it directly stimulates 5HT autoreceptors, stimulating the release of serotionin and inhibits its reuptake
(in addition to stimulating the release and inhibiting the reuptake of epinephrine, norepinephrine, and dopamine)
What are the 3 xanthine stimulants we discussed?
caffeine
theobromide
theophylline
What are the xanthine effects on the CNS in order of increasing dosage?
- stimualtes cerebral cortex, so you have clearer flow of though, lower raction time and better idea associations. less fatigue and improved manual desterity in well learned tasks
- Medullary centers affected next - stimulates respiration and vasomotor center
- large dose will affect the spinal cord, leading to hyperreflexia
What are the cardiac effects of the xanthines?
- increased HR and increased force of cotnraction, leading to increased cardiac output
- rapid (but transient) increase in CO for CHF patients (and diuresis)
- arrhythmias
- premature ventricular contractions
What is the effect of xanthines on smooth muscle?
they’re smooth muscle relaxants
decreases peripheral resistance and increases cerebral fascular resistance - so may be useful for some headaches but can worsen others
What is the proposed mechanism of action for the xanthines?
- translocation of intracellular Ca2+ from sarcoplasmic reticulum
- inhibition of phosphodiesterase, so elevated levels of cAMP
- nonselective adenosine receptor antagonist, so inhibits sleepiness-inducing adenosine
At what dose do you start to see cafeeine toxicity? About how many cups of coffee is this?
1 gm
about 80-100 cups of coffee for an average adult taken within a limited time frame
What are the CNS toxicity symptoms for caffeine?
insomnia, excitement, mild delirium, sensory disturbances
followed by convulisons! Over 10 gm you get clonic convulsions and death!
What is the toxic effect with caffeine on the GI system?
it increases gastric secretions
(even the decaffeinated coffee does this though)
What are the THERAPEUTIC uses of caffeine?
cardiac stimulation in CHF (controversial)
paroxysmal dyspnea associated with left heart failures
analeptic
bronchial asthma
migraine (with ergot alkaloids)
Do all caffeine users develop tolerance to the sleep-disrupting effects?
some do, but not all
What are the caffeine withdrawal symptoms and how soon do they occur?
headache, irritability, inability to concentrate, drowsiness, insomnia, stomach pain, joint pain
may appear within 12 to 24 hours of stopping caffeine intake
