Anticonvulsants Part 3 (Convulsants, Stimulants) Flashcards
Name the 3 convulsants
- pentylenetetrazole (Metrazole)
- strychnine
- picrotoxin
Which of the 3 convulsants blocks GABA receptors
picrotoxin
Which of the 3 convulsants decreases neuronal recovery time by increasing K permeability
pentylenetetrazole (Metrazole)
Define the action of strychnine
blocks glycine receptors on Renshaw cells (postsynaptic inhibition)
- Produces a generalized convulsion
- Added to heroin and causes overdose
- Rat poison
Define the action of picrotoxin
- Blocks GABA receptors
- Blocks GABA-induced increased chloride conductance and decreasing cAMP concentrations
- Produces conic convulsions by blocking presynaptic inhibition
Define action of pentylenetetrazole (Metrazole)
Decreases neuronal recovery time by increasing K permeability
- **Used for provocative diagnosis of epilepsy
- General cortical convulsant
Keeps people awake
Indication for Stimulants
Used as an antidote for depression = analeptics
- No one drug that is very effective
- ***Primarily used to reverse respiratory, cardiac and CNS depression
What is an analeptic
a drug that acts as a restorative
Primary classes of stimulants
- Xanthenes
- Centrally acting sympathomimetics
- Convulsants
General use for Xanthenes
Primarily used for asthma to reverse respiratory depression (Bronchodilators)
General use for centrally acting sympathomimetics
Used primarily for hyperkinetic children
- Amphetamine is prototype
2 drugs for asthma, chronic bronchitis, COPD (Xanthene)
aminophylline
theophylline
How much caffeine or theophylline is needed to increase cortical activity? How much is in an OTC stimulant?
50-200 mg (1 to 4 cups of coffee)
-*** OTC stimulants have 100-200 mg
CNS and respiratory stimulation in order of potency
- Cerebral Cortex = 50-200 mg (Small dose produces effect = more potent)
- Brain Stem = >250 mg (greater dose required)
- Spinal cord = 1000 mg (highest dose required –> **Can lead to convulsions, shakiness
Summary of Pharmacological Effects by potency/Efficacy
CNS --> caffeine = theophylline BV --> theophylline > caffeine Heart --> theophylline > caffeine SM musc --> theophylline > caffeine SK musc --> caffeine > theophyline Diuresis --> theophylline > caffeine
Describe the Blood vessel dilation effects of Xanthenes
- Blood vessel dilation (dilation in coronary and peripheral blood vessels) **BETA 2 Effect
- caffeine decreases peripheral resistance
- Can make someone hypotensive
- **theophylline more potent than caffeine
- Blood vessel Constriction (cerebral blood vessels)
- Treatment for headache
Describe the Cardiac Muscle stimulation effects of Xanthenes
Beta 1 effect
- **Increases cardiac output
- theophylline more stimulatory than caffeine
- theophylline = inhibits ADH which increases perfusion
- caffeine = hypotension (smooth muscle relaxation of vasculature in periphery), normal heart rate
- ** caffeine will cause arrhythmias in someone who is at risk for arrhythmias but does not produce arrhythmias in a normal heart
Describe the Smooth muscle relaxation effects of Xanthenes
Beta 2 effect
- Bronchial dilation; increases lung capacity to facilitate breathing
- theophylline more potent than caffeine
- *** theophylline is a popular asthma medication
Describe the Skeletal muscle effects of Xanthenes
Skeletal muscle contraction
- Caffeine more stimulatory than theophylline
- **Pain stiffness, psychic tension in neck
Causes by permeability to Ca in skeletal muscle (Contracts more than it normally would)
Describe the Diuresis effects of Xanthenes
theophylline more potent than caffeine
- increased glomerular filtration rate
- inhibits ADH
- Increased perfusion to kidney
Adverse reactions of Xanthenes
- CNS
- GI
- CVS - hyoptension
- Habit forming
How much caffeine is needed to produce toxicity
300 mg required
Withdrawal syndrome begins how soon after discontinuance with caffeine
wihtin 24 hours
2 OTC caffeine preparations
No Doz = 100 mg caffeine per tablet; recommended dose is 2 tablets
Vivarin = 200 mg caffeine tablet
Therapeutic uses of xanthenes
1- Asthma, chronic bronchitis, COPD, status asthmaticus
2- Maintains wakefulness, overcomes mild depression of CNS caused by fatigue, alcohol and sedatives
3- Some CNS depressant poisonings (Opioid poisoning)
4- Migraines - caffeine used with analgesics
5- Treatment of acute pulmonary edema and apnea in preterm infants
6- Diuretic (increases kidney perfusion, inhibits ADH)
T or F, Xanthenes are very effective in treating alcohol OD and may help to overcome mild opiate OD
1st statement False: not effective in treating alcohol OD
2nd statement True
Mechanism of Action for CNS Sympathomimetics
- Direct alpha 1 or dopamine receptor agonists
- MAO inhibitors
- Re-uptake inhibitors
- Presynaptic releasers of endogenous catecholamines
Effects of CNS sympathomimetics
- Decrease fatigue
- They don’t improve performance just allow you stop stay awake for longer
- Reduces rapid eye movement (REM)
- Produces psychic depression, parania
- May depress appetite
- Stimulates medullary respiratory center
Indications for CNS sympathomimetics
- Narcolepsy - only good therapeutic indication (30 mg/kg)
- Hyperkinetic syndromes (hyperactivity)
- Can’t concentrate for long periods of time.
Adverse effects of CNS sympathomimetics
- Acute toxicity - Xerostomia, irritability, palpitations, etc.
- Chronic toxicity - Psychosis resembling paranoid schizophrenia
- Dependency/addiction
Action of Cocaine
Blocks sodium/potassium ATP-ase reuptake mechanism
- Dopamine and NE remains in the synapse
- Rapid onset of sympathetic effects
- Reaches CNS and *causes euphoria
- Crosses blood brain barrier, which increases sympathetic effects
Drugs for ADHD
Adrenergic agonists = CNS stimulation
- methylphenidate (Ritalin) –> blocks repute of dopaminergic neurons
Stimulants
- dextroamphetamine (Dexadrine)
Selective norepinephrine reuptake inhibitor
- atomoxetine (Straterra)
What should you avoid with Ritalin
vasoconstrictors
Action of Dexadrine
- blocks the repute of dopamine and norepinephrine
- inhibits monamine oxidase
- Enhances sympathomimetic response of epinephrine/norepinephrine = avoid vasoconstrictor
Action of atomoxetine (Straterra)
Selectively inhibits repute of norepinephrine with little to no activity at other repute or receptor sites
- May increase heart rate and blood pressure in presence of a pressor agent = use vasoconstrictor with caution
Name the 3 specific amphetamines
- amphetamine (Benzedrine)
- dextroamphetamine (Dexedrine) = Narcolepsy
- ephedrine (Pretz-D)
- Cough and cold medications to relieve bronchial and nasal congestion
Amphetamines pulled from market
phenylpropanolamine (PPA)
- Deaths from heart attack and stroke
ephedra
- Deaths from heart attack and stroke - Stimulatns for performance enhancement
Amphetamines stimulate what nervous system?
Sympathetic nervous system - many cardiac effects
T or F, Use caution when administering local anesthetics with vasodilators to patients using these drugs
False, vasoconstrictors
Action of doxapram (Dopram)
Selectively stimulates respiratory centers
Indication of doxapram (Dopram)
Sold as parenteral drug to reverse general anesthesia or drug-induced respiratory depression
- also used to treat apnea in infants
Action of Nicotine
low doses of nicotine from smoke stimulates nicotinic receptors in brain stem and cortex, even though most cholinergic receptors in brain are muscarinic
T or F, higher concentrations of nicotine cause convulsions, which can be fatal. One of the most addicting substances known
True
