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Stimulants and Psychoactive Drugs: Uses, Mechanisms, and Side Effects
1.
2. Little clinical use, except methylxanthines
Can be classified in to:
› Respiratory stimulants ( Analeptics).
› Convulsants
› Psychomotor stimulants
› Psychomimetic drugs
3. Doxapram :
MOA not clear, may excite central neurons
Short acting, high margin of safety.
Low doses selective for respiratory centre
↑ Tidal volume & rate of respiration
Uses :
Post-anaesthetic resp. depression
COPD i.e. hypoxemic,hypercapnic res.fail
Apnoea in premature infants
4. Dose- 2-5mg/min(max 4mg/kg) slow i.v
infusion.
Contraindications:
Hypoxaemic, normocapnic resp.failureasthma
Resp.fail due to neurological & muscular
diseases.
Epilepsy
Side effect:
Restlessness
Tachycardia
High doses: convulsions & arrhythmias
5. No clinical use
Used as research tools
Strychnine:
Alkaloid, convulsant poison.
Spinal cord stimulant
MOA: Blocking the receptors for Glycine
In poisoning convulsion treated withDiazepam or clonazepam slow i.v
6.
7.
8. Picrotoxin:
Blocks the Cl- ion channel of GABAA.
Bicuculline:
Plant alkaloid, GABAA antagonist.
Pentylenetetrazole (PTZ):
Direct depolarization of central neurons
Provides useful animal model for testing
anticonvulsant drugs.
11. MOA: ↑DA conc. In synaptic cleft by
Enter N endings by active transport
Displace DA(also NE) from vesicles
Also inhibits MOA-B, ↓DA metabolism.
Pharmacological effects: (central)
↑ motor activity
Euphoria & excitement
Anorexia
Stereotyped & psychotic behaviour
12. ↑ BP, inhibition of GI motility
Fatigue both physical & mental reduced.
Amphetamine psychosis on repeated
use- paranoid ideas, A & T hallucinations.
PK:
Well absorbed orally
Freely penetrates BBB
Unmetabolised drug excreted in urine
14. Narcolepsy: Characterised by Sleep attacks during day time
Night mares in awakening state
Cataplexy-reversible
Methylphenedate is still used
Modafinil- devoid of abuse liability
15. Fenfluramine, dexfenfluramine used
earlier to treat obesity
Discouraged due to: Tolerance
Insomnia, pul.htn, abuse potential.
Sibutramine new drug used now
Blocks neuronal uptake of mainly NE &
5HT (also dopamine) at hypothalamic
site that regulates food intake.
16. Use:
Severe obesity with risk factors like DM.
Adverse effects:
Dry mouth
Headache
Insomnia
Constipation
↑in HR & BP
CI in CVS diseases, withdrawn from
market
18. Sudden deaths occurred with MDMA.
Induces heat stroke like conditionrhabdomyolysis & renal failure
Inappropriate secretion of ADH
Methylenedioxy amphetamine (love drug)
75mg- psychotomimetic effects
150 mg-LSD like effects
300mg- amphetamine like
SE: tachycardia, HTN, arrhythmias
19. Only caffeine if used as CNS stimulant
PK:
Oral- rapid but irregular absorption
PPB:<50%
Distributed all over the body
Met: in liver by demethylation & oxid.
Metabolites excreted in urine
T1/2: 3-6hrs
20. AE:
Gastric irritation, N, V
Nervousness, insomnia, agitation
Muscule twitch, rigidity
↑body temp,delirium, convulsions
Tachy, extra systoles at high doses
Uses:
In Analgesic mixture for headache
Migraine
Apnoea in premature infants
22. Derived from cereal fungus ergot
Hofmann synthesized & experimented on
himself.
Act as agonist at 5HT2 receptors.
Excitation threshold of retina ↓-visual
hallucinations
Excitation threshold of RAS↓-hyper
arousal state
Experiences may be bad or good trip.
23. Extract of hemp plant-C.sativa, C.indica
Bhang- paste of powdered dried
leaves, used as drink
Marijuana- dried leaves & flowering
tops, smoked in pipes or rolled as
cigarettes.
Charas or hashish- resinous exudates
leaves & flowering tops, potent smoked
inpipe.
THC content more in hashish
24. Initial CNS stimulation later sedation.
Stimulatory phaseeuphoria, ↑talkativeness, ↑appetite
Felling of confidence, relaxation & well
being
Other- analgesia, antiemetic
Peripheral effects- tachy, VD, reddening
of conjunctiva
25.
Two types CB 1& 2 receptors
CB1 in brain CB2 in periphery
Anandamide-endogenous ligand CB1.
Dronabinol, Nabilone- synt.analogues of
THC
Use: CB1 Agonists- ↑appetite in AIDS pts.
Dronabinol-antiemetic in cancer chemo.
Rimonabant : CB1 antagonist, used for
obesity, dose-20mg OD before Breakfast
Smoking cessation
26. Indications:
AD, multi infarct dementia
Mild cognitive impairment
MR, learning defects, ADHD in children
TIA, CVA, Stroke
Organic psychosyndromes
Sequale of head injury
ECT, brain surgery
27. ↑ global/regional blood flow
Direct support of neuronal metabolism
Enhancement of neurotransmission
Improvement of discrete cerebral
functions
28. Main pathological features:
Amyloid plaque
Neurofibrillary tangles
Marked ↓ in choline acetyltransferase &
loss of cholinergic neurons in brain.
29. ACEs that cross BBB are preferred.
Tacrine:
Longer acting, reversible ACE
Palliative for mild to moderate AD
Orally active
Improves memory, cognition, well being
Facilitates Ach release
AE: hepatotoxicity
30. Newer reversible Anti cholinesterase
Better penetration in to CNS
Better tolerated & less toxic than tacrine
Clinical results modest & temporary
Donepezil: 5mg OD orally evening ↑ max
10mg after 4 wks
Rivastigmine:1.5 mg orally BD ↑ to 3mg
BD after 2 wks
Galantamine:4mg BD orally ↑to 8mg BD
after 2 wks
31. Transdermal Rivastigmine patch –
applied every 24hrs
SE:diarrhoe, N, V, ↑urination
Acetyl-L-carnitine:
Structural analogue of Ach
↓ signs & symptoms of dementia in AD
↑ cholinergic transmission
Also have antioxidant properties, slows
progression of AD
32. Excitotoxicity due to enhanced
Glutamate transmission via NMDA recp.
Dose:5mg OD slowly ↑ to 10-20mg/day
Non-comp. antagonist of NMDA recp.
Better tolerated, less toxic.
Miscellaneous :
Nootropics-piracetam, aniracetam
High doses of vit E(1000 IU B.D)
Antioxidants-vit
C, A, Zn, Se, bioflavonoids or spirulina ↓
progression even in middle stage AD.