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Questions and Answers

What is a primary effect of CNS stimulants?

Reduction in anxiety

Lessening of fatigue (correct)

Increase in drowsiness

Decrease in alertness

Which of the following is an example of a psychomotor stimulant?

Lysergic acid diethyl amide

Doxapram

Strychnine

Caffeine (correct)

What potential behavioral effect can result from the misuse of CNS stimulants?

Decreased awareness

Increased drowsiness

Euphoria (correct)

Impaired concentration

What is one of the therapeutic uses of CNS stimulants?

To counteract fatigue Signup and view all the answers

Which of the following drugs is categorized as an analeptic?

Nikethamide Signup and view all the answers

What is a common side effect associated with CNS stimulants?

Heightened anxiety Signup and view all the answers

Which neurotransmission process is enhanced by stimulants like amphetamines?

Excitatory neurotransmission Signup and view all the answers

What characterizes convulsant drugs like Strychnine?

Induce seizures Signup and view all the answers

What is the primary mechanism of action for psychomotor stimulants?

They inhibit reuptake mechanisms for several biogenic amines. Signup and view all the answers

Which of the following compounds is a piperidine derivative?

Methylphenidate Signup and view all the answers

Which of the following compounds primarily acts as an anorectic?

Methamphetamine Signup and view all the answers

What is the role of α-adrenergic receptor stimulation in psychomotor stimulants?

It increases heart rate and blood pressure. Signup and view all the answers

Which methylxanthine is known to block adenosine A1-receptors?

Caffeine Signup and view all the answers

Among the listed psychomotor stimulants, which compound is known to have the highest potential for abuse?

Methamphetamine Signup and view all the answers

What is the chemical structure modification that differentiates methamphetamine from amphetamine?

Methyl group substitution at R1 Signup and view all the answers

Which of the following statements about theobromine is true?

It is a weaker stimulant compared to caffeine. Signup and view all the answers

What is the primary effect of adenosine in the bronchial muscles?

Contraction Signup and view all the answers

How do methylxanthines, such as theophylline, primarily enhance bronchodilation?

By inhibiting phosphodiesterase Signup and view all the answers

What type of convulsions does strychnine primarily produce?

Tonic-clonic and symmetrical convulsions Signup and view all the answers

What specific action does doxapram have as a respiratory stimulant?

Increases neuronal excitability Signup and view all the answers

Which drug acts as a hallucinogen primarily through 5-HT receptor agonism?

Lysergic acid diethylamide (LSD) Signup and view all the answers

What is the mechanism of action of picrotoxin as a convulsant?

Blocking GABA-mediated inhibition Signup and view all the answers

Which drug is an example of an antiasthmatic agent with a potent bronchodilatory effect compared to caffeine?

Aminophylline Signup and view all the answers

What is the therapeutic indication currently valid for pentylenetetrazol?

CNS stimulation Signup and view all the answers

Study Notes

CNS Stimulants

CNS stimulants temporarily increase alertness and awareness.
More potent stimulants often have more adverse effects and are therefore prescription medicines or illicit drugs.
Stimulants increase the activity of the sympathetic system, central nervous system, or both.
Some stimulants produce a sense of euphoria, particularly those that act on the CNS.

Therapeutic Uses of CNS Stimulants

Increase or maintain alertness.
Counteract fatigue when sleep is not practical, such as while operating vehicles.
Counteract abnormal states that diminish alertness or consciousness, such as in narcolepsy.
Promote weight loss (anorectics).
Enhance concentration in those with attentional disruptions.

The mechanisms underlying CNS stimulation are complex and involve various neurotransmitters and neural pathways. An imbalance occurs primarily between the inhibitory neurotransmitters, such as gamma-aminobutyric acid (GABA), and excitatory ones like glutamate. This differential modulation results in heightened neuronal activity, contributing to the overall increase in alertness, energy, and stimulation experienced by the individual.

Classification of CNS Stimulants

Psychomotor Stimulants (Central Stimulant Sympathomimetics):
- β–Phenylethylamine derivatives: Amphetamines and related drugs.
- Methylxanthines: Caffeine, Theophylline, Theobromine, Aminophylline, Etophylline, Methylphenidate.
Analeptics (Respiratory Stimulants): Doxapram, Nikethamide.
Convulsants: Strychnine, Picrotoxin, Pentylenetetrazol.
Psychotomimetic Drugs: Hallucinogenic drugs (Lysergic acid diethyl amide, Phencyclidine, Cannabis).

β–Phenylethylamine Derivatives (Amphetamines)

Structure: Amphetamines are derivatives of β–Phenylethylamine with variations in their substituent groups.
Examples: Amphetamine, Methamphetamine, Phentermine, Benzphetamine.
Mechanism of Action: Amphetamines work primarily by inhibiting the reuptake of important neurotransmitters known as biogenic amines, specifically dopamine, norepinephrine, and serotonin. This results in an increased concentration of these neurotransmitters in the synaptic cleft, leading to enhanced catecholamine release and the inhibition of monoamine oxidase, an enzyme responsible for degrading these neurotransmitters..
Uses: Used for weight loss (anorectics).

Methylphenidate

Structure: A piperidine derivative with a cyanophenylmethylsodium group.
Mechanism of Action: Blocks norepinephrine uptake and acts as a postsynaptic agonist.

Methylxanthines

Structure: Methylxanthines are derived from theobromine and have variations in their substituent groups.
Examples: Caffeine, Theophylline, Theobromine, Etophylline.
Sources: Thea sinensis (tea), Theobroma cacao (coffee).
Mechanism of Action: Block adenosine A1-receptors. Adenosine acts as a local mediator in the CNS, cardiovascular system, and other organs. Methylxanthines also inhibit phosphodiesterase, which degrades intracellular cAMP.
Uses:
- Caffeine: Treatment of migraine along with ergotamine; used with analgesics.
- Theophylline: Antiasthmatic (bronchodilation) effect is more potent than that of caffeine. Produces slow but sustained dose-related bronchodilation.

Analeptics (Respiratory Stimulants)

Examples: Doxapram, Nikethamide.
Mechanism of Action: Direct-acting stimulants that increase neuronal excitability by decreasing neuronal recovery time or by increasing responsiveness to excitatory neurotransmitters.
Uses:
- Doxapram: Claimed to be a specific respiratory stimulant for drug-induced respiratory depression, but supportive treatment is often more effective. Sometimes used in anesthesia.
- Nikethamide: Used for excessive CNS depression and respiratory depression.

Convulsants

Examples: Strychnine, Picrotoxin, Pentylenetetrazol.
Strychnine: An alkaloid derived from Strychnos nux vomica seeds. Acts by blocking post-synaptic inhibition produced by the inhibitory transmitter glycine.
Picrotoxin: Obtained from Anamirta cocculus. Produces asymmetrical clonic convulsions by blocking GABA-mediated inhibition and chloride channels.
Pentylenetetrazol: A powerful CNS stimulant that acts by direct depolarization of central neurons. Also inhibits GABA neurotransmission.

Psychotomimetic Drugs (Hallucinogenic Drugs)

Examples: Lysergic acid diethyl amide (LSD), Phencyclidine, Cannabis.
LSD: Acts as a 5-HT (serotonin) receptor agonist in the CNS.
THC (Tetrahydrocannabinol): Binds to specific cannabinoid (CB) receptors located in various brain areas.