Clinical Toxicology: CNS Stimulants and Amphetamines

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Questions and Answers

What is one of the primary pharmacological actions of caffeine?

Promoting bronchodilation (correct)

Decreasing norepinephrine levels

Enhancing the effects of benzodiazepines

Inhibiting serotonin reuptake

Which methylxanthine derivative is primarily associated with the use of caffeine in drug therapy?

Cacao

Salicylates

Theobromine

Theophylline (correct)

Which factor can affect the clearance of theophylline in the body?

Frequency of exercise

Amount of water intake

Temperature variations

Presence of other drugs (correct)

What is the therapeutic blood concentration range for theophylline?

10 to 20 μg/mL Signup and view all the answers

What is a potential consequence of rapid intravenous administration of theophylline?

Cardiac arrhythmias Signup and view all the answers

What is diazepam typically used for in cases of theophylline toxicity?

Controlling seizures Signup and view all the answers

Which cyclic nucleotide is notably accumulated due to methylxanthine toxicity?

Cyclic AMP Signup and view all the answers

What is a common manifestation of theophylline overdose?

Seizures Signup and view all the answers

What can be used to manage arrhythmias induced by theophylline toxicity?

Propranolol Signup and view all the answers

Which methylxanthine has a weaker pharmacological activity on the central nervous system compared to caffeine?

Theobromine Signup and view all the answers

What is the primary reason camphor-related poisonings occur?

Mistaking camphorated oil for castor oil or similar remedies Signup and view all the answers

What should be done first in the management of camphor poisoning?

Induction of emesis or gastric lavage Signup and view all the answers

Which of the following accurately reflects the time frame for symptoms to appear after camphor ingestion?

Between 5 to 15 minutes or delayed for several hours Signup and view all the answers

Why is diazepam preferred over barbiturates in managing convulsions from camphor poisoning?

Diazepam produces less respiratory depression Signup and view all the answers

What is the purpose of using hemodialysis in camphor poisoning?

To accelerate the removal of camphor from the blood Signup and view all the answers

How should the patient be managed in terms of environmental stimuli during treatment for camphor poisoning?

Kept quiet and with minimum sensory input Signup and view all the answers

Which of the following should be continued until the camphor odor is no longer detected?

Gastric lavage Signup and view all the answers

What is one of the primary mechanisms of toxicity associated with amphetamines?

Causing the release of catecholamines into central synaptic spaces Signup and view all the answers

What dosage assumption is recommended if the quantity of camphor ingested is unknown?

Assume it was greater than 1 g Signup and view all the answers

Which of the following roles does succinylcholine play in the treatment of camphor poisoning?

It helps control muscular rigidity and spasm Signup and view all the answers

Which of the following symptoms is NOT typically associated with amphetamine poisoning?

Severe respiratory depression Signup and view all the answers

Which treatment is recommended for managing amphetamine-induced psychosis?

Chlorpromazine Signup and view all the answers

What is a common misconception about camphor-containing products?

They are not toxic at all Signup and view all the answers

What effect may occur as a result of prolonged amphetamine use, specifically regarding doses?

Development of tolerance to the euphoric effects Signup and view all the answers

In the management of hyperthermia caused by amphetamine toxicity, which approach is NOT recommended?

Providing warm fluids Signup and view all the answers

Which cardiovascular effect is commonly associated with amphetamine use?

Hypertension Signup and view all the answers

What is a potential fatal consequence of high amphetamine induced hyperpyrexia?

Incompatibility with life Signup and view all the answers

Which type of hallucination is most commonly associated with chronic amphetamine use?

Auditory hallucinations with chronic use Signup and view all the answers

What characterizes the sympathomimetic effects of amphetamines?

Increased rate of perspiration and flushing Signup and view all the answers

What is a characteristic sign of amphetamine overdose?

Psychosis with hallucinations Signup and view all the answers

Study Notes

Clinical Toxicology: Central Nervous System Stimulants (Amphetamines)

Amphetamines modify various medical conditions
Approved for narcolepsy, hyperactivity in children, and short-term obesity treatment

Mechanism of Toxicity

Amphetamines stimulate the CNS by:
- Releasing catecholamines (epinephrine, norepinephrine, dopamine) into synaptic spaces
- Inhibiting reuptake of these neurotransmitters
Tolerance develops, requiring increasing doses
Continued use can lower the convulsive threshold, increasing fatality risk

Characteristics of Poisoning

Amphetamines cause dose-related signs and symptoms, extending pharmacological actions
- Central Nervous System (CNS):
  - Psychosis with euphoria and hallucinations (common)
    - Auditory hallucinations (chronic use)
    - Visual hallucinations (large dose)
    - Tactile hallucinations (occasional)
- Respiratory: Stimulation
- Cardiovascular: Stimulation (tachycardia, hypertension)
- Sympathomimetic effects: Flushing, diaphoresis
- Hyperthermia: Temperatures above 109°F (42.8°C) can be life-threatening

Methylxanthine Derivatives

Three methylxanthine alkaloids commonly found in natural resources:
- Theobromine (Cocoa, chocolate)
- Theophylline (Tea)
- Caffeine (Tea, coffee, cola drinks, cocoa, chocolate)
Used in drug therapy

Methylxanthines

Stimulate the central nervous system (CNS)
Cause:
- Diuresis
- Relaxation of bronchial muscles
- Stimulation of cardiac function
Caffeine enhances analgesic effects of salicylates
Theobromine has milder CNS effects than caffeine

Mechanism of Methylxanthine Toxicity

Increased calcium release from intracellular sites
Accumulation of cyclic AMP (cAMP) and other cyclic nucleotides, particularly by phosphodiesterase inhibitors (important second messengers in cellular responses)
Adenosine receptor blockade, increasing norepinephrine, dopamine, and serotonin release

Theophylline Poisoning

Narrow therapeutic margin (10-20 µg/mL)
Maintaining therapeutic levels can be challenging
Rapid IV administration can cause arrhythmias
Signs of overdose: nausea, vomiting, headache, dizziness, palpitations, tachycardia, hypotension, precordial pain, restlessness, agitation, and occasionally seizures

Camphor Poisoning

Rapid CNS entry due to high lipid solubility
Signs and symptoms appear within 5-15 minutes of ingestion sometimes delayed
Management:
- Stomach emptying (emesis, lavage)
- Activated charcoal administration
- Continue until camphor odor is gone
  - If the amount ingested is unknown, treat as if it were a larger than usual dose (greater than 1g)
Treatment:
- Diazepam (often first line for seizures), followed by phenobarbital if needed
- Propranolol or verapamil to control arrhythmias and reverse hypotension
- Hemodialysis to remove camphor from the blood

Other Management Considerations

Barbiturates (used to control convulsions, but diazepam is generally preferred because it causes less respiratory depression)
Succinylcholine to control muscle rigidity and spasms

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Description

Explore the mechanisms, toxicity, and symptoms associated with amphetamines as central nervous system stimulants. This quiz covers their medical uses, effects on neurotransmitters, and the characteristics of poisoning. Test your knowledge on their impact on various systems in the body.