Overview & Classes - Brain's Fast Lane
Psychostimulants: Drugs that ↑ alertness, wakefulness, & locomotor activity.
- Core MOA: Potentiate catecholamine (Dopamine, Norepinephrine) effects.
- Key Uses: ADHD, narcolepsy.
- Major Risk: High abuse potential.
Classification of Psychostimulants:
| Class | Examples | MoA (Primary) |
|---|---|---|
| Amphetamines | Amphetamine, Methamphetamine | ↑ DA/NE release & ↓ reuptake |
| Methylphenidate | Methylphenidate | Blocks DA/NE reuptake |
| Xanthines | Caffeine, Theophylline | Adenosine antag., PDE inhib. |
| Modafinil | Modafinil, Armodafinil | Atypical (?DAT inh.) |
| Cocaine | Cocaine | Blocks DA/NE/5-HT reuptake |
MoA & Pharmacokinetics - Neurotransmitter Party
- Mechanism of Action (MoA): General effect: ↑ synaptic Dopamine (DA), Norepinephrine (NE), & Serotonin (5-HT).
- 📌 Mnemonic: Stimulants ARE UP (Amphetamines Release Efflux; Uptake blocked by Phenidates/Cocaine).
- Amphetamines & derivatives: Promote NT release from presynaptic vesicles.
- Cocaine, Methylphenidate: Inhibit reuptake transporters (DAT, NET, SERT).
- Pharmacokinetics (PK):
- Absorption: Rapid (oral, IV, inhalation).
- Distribution: Highly lipid-soluble, readily cross Blood-Brain Barrier (BBB).
- Metabolism: Primarily hepatic (e.g., CYP2D6 for amphetamine).
- Excretion: Renal; urine pH influences amphetamine excretion (acidic pH ↑ excretion).
⭐ Cocaine is unique among psychostimulants for its additional action as a sodium channel blocker, leading to local anesthetic effects.
Specific Drugs & Indications - Focus & Wakefulness
| Drug | Primary MoA | Key Use(s) | Unique Side Effect/Note |
|---|---|---|---|
| Methylphenidate | NET & DAT block; ↑ DA/NE | ADHD, Narcolepsy | Insomnia, ↓Appetite, headache; 📌 MPH: More Productive Hours (less sleep/food) |
| Amphetamine | ↑ NE/DA release; NET/DAT block | ADHD, Narcolepsy, Binge eating disorder | Psychosis risk, Abuse potential, HTN; Growth delay (children) |
| Modafinil | Atypical DAT block; ↑ Histamine, Orexin; ↓ GABA | Narcolepsy, SWSD, OSA (adjunct) | SJS (rare), headache; Less abuse potential than amphetamines |
| Atomoxetine | Selective NET block (SNRI); ↑ NE in PFC | ADHD (esp. with substance abuse risk/tics) | Non-stimulant; Suicidal ideation (BBW); Hepatotoxicity, Somnolence |
Adverse Effects & Cautions - Handle With Care
- Common Adverse Effects:
- CNS: Insomnia, anxiety, irritability, nervousness, headache.
- CVS: Tachycardia, palpitations, ↑BP.
- GI: Anorexia, weight loss, dry mouth, nausea.
- Serious Adverse Effects:
- Dependence, tolerance, withdrawal symptoms.
- Psychotic episodes, hallucinations (especially with abuse).
- Seizures (may lower threshold).
- Cardiovascular events (MI, stroke, sudden death in those with pre-existing cardiac conditions).
- Growth suppression in children (monitor height/weight).
- Contraindications & Cautions: ⚠️
- Known hypersensitivity.
- Symptomatic cardiovascular disease (arrhythmias, severe hypertension).
- Glaucoma (angle-closure).
- Hyperthyroidism.
- Agitated states, severe anxiety.
- History of drug abuse.
- Tourette’s syndrome or tics.
- MAOI use (concurrently or within 14 days).
⭐ Concomitant use of psychostimulants (e.g., amphetamine, methylphenidate) with MAOIs is contraindicated. This combination poses a high risk of life-threatening hypertensive crisis due to synergistic increases in synaptic norepinephrine.
High‑Yield Points - ⚡ Biggest Takeaways
- Psychostimulants primarily ↑ DA & NE; cocaine blocks reuptake, amphetamines also promote release.
- Key uses: ADHD (methylphenidate, amphetamines), narcolepsy (modafinil, amphetamines).
- Methylphenidate: Common for ADHD, acts by blocking DAT and NET.
- Adverse effects: Sympathomimetic (tachycardia, HTN), insomnia, psychosis; risk of dependence & withdrawal.
- Cocaine uniquely blocks Na+ channels (local anesthetic effect) & causes coronary vasospasm.
- Modafinil is an atypical stimulant for narcolepsy with lower abuse potential than amphetamines.
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