This document defines stimulants and analeptics as substances that increase behavioral activity and stimulate the central nervous system (CNS) and respiration. It describes several classes of CNS stimulants based on their site of action, including cortical, medullary, and spinal stimulants. Common stimulants like amphetamines, cocaine, and caffeine are discussed. The document also summarizes the mechanisms of action, pharmacological effects, pharmacokinetics, therapeutic uses, and adverse effects of xanthine alkaloids like caffeine, theophylline, and theobromine.

1. Definition:
 Stimulants are a substance which tend to
increase behavioural activity when
administered.
Stimulants of CNS do not have a selective
action. Excessive stimulation of CNS is
followed depression. So these drugs are not
therapeutically useful. Some of these drugs
are used as analeptics.
CNS Stimulants
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2. ANALEPTICS
Analeptics are drugs which stimulate the CNS.
They also stimulate the respiration.
In larger doses they produce convulsions.
SIGNS AND SYMPTOMS:
 Elevate mood,
 Increase motor activity,
 Increase alertness,
 Decrease need for sleep,
 In case of over dose leads to convulsions and
death
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3. classification
• According to their site of action
1.Direct CNS stimulants/psychomotor
stimulants:
A. Cortical stimulants/cerebral stimulants:
Site of action: cerebral cortex
EX:- Xanthine alkaloids (methyl
xanthines),amphetamine, cocaine,
pipradrol,methyl phenidate
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4. B. Medullary stimulants/respiratory stimulants:
Site of action: Medulla oblongata
EX:- Picrotoxin, PTZ (Pentylene tetrazol)-
convulants,
Nikethamide, amiphenazole, bemigride,
doxapram.
C. Spinal stimulants/spinal cord stimulants:
Site of action: Spinal cord
EX:- Strychnine, leptazol- convulants,
2.Reflex stimulants:
EX:- Lobeline, nicotine,ammonia,veratrum.
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5. M.O.A of CNS stimulants
 Stimulate the CNS
 Increase the heart and breathing rate & brain
function
 Stimulants leading to an increased release of
neurotransmitter
 Relaxing bronchi and cold medicine for
medical purpose
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6. Pharmacology of xanthine (methyl
xanthine alkaloids)
The three xanthine alkaloids are
 Caffeine: present in seeds of Coffea arabica
(coffee seeds)
 Theophylline: present in the leaves of Thea
sinesis (tea leaves)
 Theobromine: present in the seeds of
Theobromo cocoa (cocoa seeds)
These are naturally occurring alkaloids. The
beverages like coffee contains caffeine, tea
contains theophylline and caffeine, cocoa
contains caffeine and theobromine.
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7. Pharmacological actions
1. CNS:- caffeine stimulate cerebral cortex in
CNS. It induces clear flow of thoughts and
association of ideas. Motor activity will be
increased and fatigue is delayed but in larger
doses caffeine produces headache, confusion
and delirium and also produces the
stimulation of respiratory vagus and
vasomotor centers.
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8. 2.CVS:- Xanthines produces direct stimulant
effect on myocardium (i.e. Increase in force of
contraction- increase in heart rate-increase in
cardiac out put-increase in peripheral
vasodilatation-increase in BP). Also they
produce dilation of coronary and pulmonary
blood vessels.
3.Miscellaneous effects:- xanthine produces
A.Smooth muscle:- Relaxation of bronchial
smooth muscle
B.GIT:- Increase the secretion of acid and
pepsin in stomach and are gastric irritant.
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9. C. Skeletal muscle:- Enhances the power of
muscle contraction.
D.Kidney:- Diuretic effect.
Pharmacokinetics:-
Well absorbed on oral and parenteral
administration.
They are metabolized in liver by Phase-1
reactions.
The metabolic products are excreted in urine.
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10. Advere effects:-
 Nausea, vomiting, epigastric pain
and ulcer-----GI effects.
Confusion,insomina,excitment,deliri
um,nervousness,tremors,tachycardia
,hypotension,arrhythmias,headache-
---CNS effects.
High dose produces convulsions.
Tolerance and habituation.
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11. Therapeutic uses:-
Bronchial asthma / anti-asthmatic agents
Diuretics
Anti- drepressants
Coronary vasodilator
Head ache-------
Caffeine + ergotamine---- migrane headache,
Caffeine+ paracetamol/aspirin--- headache
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