Drugs acting on Central Nervous System

A. General anesthetics:

1. Gas: Nitrous oxide
2. Volatile liqiuds: Halothane, Isoflurane, Desflurane, Sevoflurane, Ether

1. Fast-acting drugs (Inducing drugs): Propofol, Etomidate, Thiopentone, Methohexitone
2. Slow-acting drugs:
   • Benzodiazepines: Diazepam, lorazepam, midazolam
   • Dissoiative anaesthetic: Ketamine
   • Opioids: Fentanyl, alfentanil, sufentanil, remifentanil

B. Local anesthetics:

1. Esters: Cocaine, procaine, chloroprocaine, benzocaine, tetracaine
2. Amides: Lignocaine, mepivacaine, bupivacaine, prilocaine, articaine, ropivacaine

1. Surface anaesthetics: Cocaine, lignocaine, tetracaine, benzocaine, oxethazaine, proparacaine, butylaminobenzoate
2. Injectable anaesthetics:
   • Short acting and low potency: Procaine, chloroprocaine
   • Intermediate acting and potency: Lignocaine, mepivacaine, prilocaine, articaine
   • Long acting and high potentcy: Tetracaine, bupivacaine, dibucaine, ropivacaine

C. Preanesthetic medication drugs:

1. Sedative-antianxiety drugs: Diazepam, lorazepam, promethazine
2. Opioids: Morphine, pethidine
3. Anticholinergic drugs: Atropine, Hyoscine, Glycopyrrolate
4. Neuroleptics: Chlorpromazine, triflupromazine, haloperidol
5. Antiemetics: Metoclopramide, domperidone, Ondansetron
6. Gastric acid suppressant drugs: Ranitidine, Famotidine, Omeprazole, Pantoprazole

D. Sedatives and Hypnotics:

1. Benzodiazepines:
   • All these drugs have a benzene ring fused to a 7-membered diazepine ring.
   • They act at Midbrain (ascending reticular formation), limbic system, brain stem, etc.
   • BZDs are typically administered orally, intravenously, or rectally, with oral absorption being variable. They have a large volume of distribution and a short duration of action due to rapid redistribution, preventing hangover effects despite a long elimination half-life.
   • BZDs are generally well-tolerated with common side effects including drowsiness and confusion. Chronic use may lead to withdrawal symptoms (like Insomnia, tremor, nrvousness and restlessness) and paradoxical effects (convulsions and anxiety) in some patients.
   • Ex: Diazepam, lorazepam, promethazine
2. Barbiturates:
   • Long acting: Phenobarbitone
   • Short acting: Butobarbitone, pentobarbitone
   • Ultrashort acting: Thiopentone, methohexitone
3. Nonbenzodiazepine hypnotics:
   • They have less antianxiety, anticonvulsant and muscle relaxant effects than BZDs.
   • Effect on REM sleep is less as compared to BZDs.
   • Zolpidem, zopiclone, zaleplon, eszopiclone
4. Others: Melatonin, ramelteon, suvorexant

E. Alcohols:

• Alcohols can be detected by breath analyser as it is present in exhaled air
• Ex: Methanol and Ethanol

F. Antiepileptic drugs:

1. Barbiturate: Phenobarbitone
2. Deoxyarbiturate: Primidone
3. Hydantoin: Phenytoin, fosphenytoin
4. Succiinimide: Ethosuximide
5. Iminostilbene: Carbamazepam, Oxcarbazepine, eslicrbazepine
6. Aliphatic carboxylic acid: Valproate, divalproex
7. Benzodiazepines: Diazepam, clonazepam, lorazepam, clobazam
8. Phenyltriazine: Lamotrigine
9. Cyclic GABA analogues: Gabapentin, pregabalin
10. Other drugs: Topiramate, zonisamide, levetiracetam, vigabatrin

G. Opioid analgesics:

1. opioid agonists:
   • Natural opioid alkaloids: Morphine, codeine
   • Semisynthetic opioids: Diacetyllmorphine (Heroin), pholcodine, ethylmorphine
   • Synthetic opioids: Pethidine, tramadol, tapentadol, methadone, dextropropoxyphene, fentanyl, alfentanil, sufentanil, remifentanil
2. complex action opioids:
   • Opioid agonist-antagonist (k analgesics): Pentazocine, butorphanol, nalorphine, nalbuphine
   • Partial µ receptor agonist and k receptor antagonist: Buprenorphine
3. Pure opioid antagonist: Naloxone, naltrexone, nalmeferene

F. Antiparkinsonian drugs:

1. Drugs affecting brain dopaminergic system:
   • Dopamine precursor: Levodopa (L-Dopa)
   • Dopamine agonists: Bromocriptine, pramipexole, ropinirole
   • NMDA-receptor antagonist: Amantadine
   • Monoamine oxidase (MAO)-B inhibitors: Selegiline (deprenyl), rasagiline
   • Catechol-O-methyltransferase (COMT) inhibitors: Tolcapone, entacapone
2. Drugs affecting brain cholinergic system:
   • Centrally acting anticholinergic drugs: Benztropine, benzhexol (trihexyphenidyl), procyclidine, biperiden
   • Antihistaminics (H1-blockers) with anticholinergic activity: Promethazine, diphenhydramine, orphenadrine

G. Antipsychotics:

1. Phenothiazines:
   • Aliphatic side chain: Chlorpromazine, triflupromazine
   • Piperidine side chain: Thioridazine
   • Piperazine side chain: Trifluoperazine, fluphenazine
2. Thioxanthenes: Flupenthixol
3. Butyrophenones: Haloperidol, trifluperidol
4. Atypical antipsychotics: Risperidone, clozapine, olanzapine, quetiapine, zotepine, aripiprazole, amisulpride, ziprasidone
5. Others: Loxapine, pimozide, levosulpiride

H. Antianxiety:

1. Benzodiazepines: Diazepam, oxazepam, clonazepam, lorazepam, Chlordiazepoxide
2. Azapirones: Buspirone, Gepirone, Ispapirone
3. Sedative-antihistaminic drugs: Hydroxizine
4. β-adrenergic blocker: Propanolol

I. Antidepressants:

1. Tricyclic antidepressants:
   • NA + 5-HT reuptake inhibitor: Amitriptyline, imipramime, trimipramime, Doxepin, Dothiepin, clomipramine
   • Predominantly NA reuptake inhibitors: Desipramine, Nortriptyline, Protriptyline
2. Selective serotonin (5-HT) reuptake inhibitors (SSRIs): Fluoxetine, fluvoxamine, citalopram, escitalopram, sertraline, paroxetine, dapoxetine
3. Serotonin and noradrenaline reuptake inhibitors (SNRIs): Duloxetine, venlafaxine, desvenlafaxine
4. Atypical antidepressants: Trazodone, bupropion, mianserin, mirtazapine, atomoxetine
5. Reversible ihibitors of MAO-A inhibitors (RIMAs): Moclobemide, clorgyline

J. Hallucinogens:

1. Indole alkylamines: Lysergic acid diethylamide (LSD), Lysergic acid amide, psilocybin, harmine, diethyltryptamine
2. Phenylalklamines: Mescaline, Ecstasy (Methylene dioxymethamphetamine), YABA
3. Arylcyclohexylamine: Phencyclidine
4. Cannabinoids: Tetrahydrocannabinoid

K. CNS stimulants:

1. Convulsants: Strychnine, picrotoxin, bicuculine, pentylenetetrazole
2. Analeptic: Doxapram
3. Psychostimulants: Amphetamines, methyl phenidate, sextroamphetamine, atomoxetine, modafinil, armodafinil, cocaine, caffeine

L. Cognitive enhancers (Nootropics):

1. Cholinergic activators: Rivastigmine, donepezil, galantamine, tacrine
2. Glutamate (NMDA receptor) antagonist: Memantine
3. Miscellaneous drugs: Piracetam, pyritinol, dihydroergotoxine (codergocrine), Citicoline, piribedil, gingko biloba

M. Drugs for mania and bipolar disorder:

• Bipolar disorder, also known as manic-depressive illness, is a psychiatric condition characterized by alternating episodes of depression with mania. Mania, an affective disorder, is marked by heightened mood, increased energy, agitation, hyperactivity, and uncontrolled thoughts and speech.
• Ex:
  1. Lithium (First drug used for the treatment of mania)
  2. Anticonvulsants: Sodium valproate, carbamazepine, lamotrigine
  3. Atypical antipsychotics: Olanzapine, risperidone, quetiapine, aripiprazole