Classification
1.
of
Antimuscarinic Agents
Naturalalkaloids (Belladonna alkaloids): AtrOpine, scopolamine (hyoscne).
Semisynthetic derivatives: Hyoscine butyl bromide, Honmatropine (mydriatic), pratropium
bromide, tiotropium bromide (bronchial asthma).
3. Syntheticantimuscarinic agents:
(a) Used as mydriatic - cyclopentolate, tropicamide
(b) Used in pepticulcer - pirenzepine, telenzepine, clidinium, propantheline
(c) Used as antispasmodic - dicyclomine, valethamate, flavoxate, oxybutynin, tolterodine,
darifenacin, solifenacin
(d) Used as preanaesthetic agent - glycopyrrolate
(e) Used in parkinsonism -benzhexol (trihexyphenidyl), benztropine, biperiden, procycidine
Atropine. Atropine is the prototype drug and the chief alkaloid of belladonna. It is a tertiary
amine. It blocksactions of ACh on all the muscarinic receptors. Atropine is administered by
topical (eye), oral and parenteral routes.
CLASSIFICATION
Skeletal muscle relaxants
Centrally acting
" Diazepam and other
Peripherally acting
benzodiazepines
" Methocarbamol
. ChlorzOxazone
. Tizanidine
"Baclofen Drugs acting at Directly acting on
" Carisoprodol NMJ skeletal muscle
" Thiocolchicoside " Dantrolene
Depolarizing blockers Nondepolarising blockers Others
"Succinylcholine (competitive blockers) " Botulinum toxin A
"Decamethonium " d-TC
"Pancuronium
" Doxacurium Long acting
" Pipecuronium)
Vecuronium
" Rocuronium
Intermediate
" Rapacuronium
" Atracurium acting
" Cisatracurium
"Mivacurium Short acting
a-ADRENERGIC BLOCKERS
Classification PHIR
a-blockers
Nonselective Selective
(a, and O) Selective
a,-blockers ay-blocker
blockers
" Prazosin
" Yohimbine
" Terazosin
" Doxazosin
Reversible Irreversible
Tamsulosin
" Phentolamine " Phenoxybenzamine " Silodosin
" Alfuzosin
B-ADRENERGIC BLOCKERS
B-Adrenergic
and drugs. block the B-receptor-mediated effects of sympathetic stimulatio
adrenergicantagonists
CLASSIFICATION
B-blockers
First generation Second generation Third generation
(nonselective (B-selective (B-blockers with
B-adrenergic blockers) adrenergic blockers) additional vasodilatory effect)
" Propranolol " Atenolol
" Timolol . Acebutolol
" Pindolol Bisoprolol
" Sotalol " Esmolol Nonselective B-Selective
Metoprolol " Labetalol " Betaxolol
" Carvedilol " Celiproll
Nebivolol
Pindolol, acebutololand labetalol have partial agonistic activity (intrinsic sympathomimetic
activity [ISA). They stimulate B-receptors partially in the absence of catecholamines.
Propranolol, pindolol, acebutolol, metoprolol and labetalol have membrane-stabilizing
activity (local anaesthetic activity).
Mechanism of action. Propranolol is the prototype drug. B-Blockers competitively block the
B-receptor-mediated actions of catecholamines and other adrenergic agonists.
Catecholamines and other Propranolol and other
B-Receptors B-blockers (antagonists)
adrenergic agonists
Classification
sympathomimetic
1. also The
(D) (a)
the
On ADRENERGI
referred
C
mines:
es,
e.g. called
Catecholamines:
basis
catecholamines, to
of of as
(SYMPATHOMIMETICS) DRUGS
Adrenergic
theiradrenergic
Sympathomimetics drugs
e, chemical
etics
e.g. Drugsagonists.mimic
HO
e, HO4 adrenaline,structure
(Sympathomimetics)
3
effects
2
with of
ne
e,and that 6 NA,
catechol sympathetic
DA,
lack
isoprenaline
nucleus
techol
stimulation
ucleus (3,4-dihydroxy
and
dobutamine. (Fig.
are
called 4.20).
ol. benzene)
They
oncate
are are
2
5
3+ 6
7+
Fig. 4.20 An angry man symbolizing the sympathetic overactivity (fight-right-flight) - 1, anger, alert, agg=
sive; 2, pupillary dilatation (mydriasis); 3, increased muscle tone, trermors; 4, palpitation, increased cata
output-increased blood flow to skeletal muscles; 5, flushing of the face: 6, tachypnoea, bronchodiatatr
7. liver - glycogenolysis ’ more energy; 8, adipose. tissue ’
lipolysis ’ energy.
2. On thebasis of their mechanism of action (Table
(a) Direct acting: They act directly by 4.12):
(b) Indirect acting: They act by stimulating adrenergic receptors.
(c) Mixed acting: These drugs actreleasing NA from adrenergicnerve endings.
both directly and indirectly.
3. On the basis of their therapeutic use:
vasopressor:
(a) As vasopressOr: NA,
termine.
dopamine, ephedrine, phenylephrine, methoxamine Imephet
(b) As bronchodilator: Salbutamol,
formoterol. levalbuterol, terbutaline, bambuterol, salmeterol and
(c) As cardiac stimulant: AdAdrenaline,
(d) As CNS stimulant: Amphetamine,
isoprernaline and dobutamine.
(e) As nasal decongestant: Phenylephrine, dextxylroamnphet
ometa a
zolimi
n n
and
e, e methamphet aOxymetazoline
mine.
and naphazoline.
() As anorexiant: Amphetamine, mazindol, phentermine and pseudoephedrine,
(g) As uterine relaxant: Isoxsuprine, terbutaline, salbutamol andsibutramine.
ritodrine.
Mixed 3. Indirectiy
acting 2. Directacting
By1.
AdrenalineADRENERGIC ab4,le12
acting Formoterol Levalbuterol
" " Noradrenaline "
Dopamine " Ephedrine "Brimonidine
" Amphetamine
Methylphenidate " "Oxymetazoline
"Naphazoline
" Xylometazoline " Isoxsuprine
" Methoxamine " " Salbutamol "
ermine Methamphetamine Apraclonidine Ritodrine Phernylephrine eterolalin(ealbuterol)
SalmTerbut DobutaminIseoprenaline
AGONISummar
STS y
a, B-agonists;
aet a1-agonists
They ag-Agonists ag-agonists SelectiveSelective
main Bz-agonists selectiveB-agonistandB1- a1,andag-
Selective B-agonist
Relatively RECEPTOR
gonistreleasesNAa1,action)
action) periphery; action
uterus
on -,, of
a2, hydroxytryptamine
a2, centrally
(5-H) act
B B1
by
Sympathomimetic
Bi
and +and B-agonist; ACTION
eases
+ releases releasing
NA, B2
D B2 and
agonist agonist DA
NA and NA no
Ba-agonist
NA
t(indirect
(direct 5 in Agents
Bz
the action
BronchialCardiogenic HeartSeptic Anaphylactic THERAPEUTIC
USES
Intravenous attention-deficit
Narcolepsy,
hyperac Glaucoma
(topical) NasalHypotension relaxants
Uterine
tensiCardiogenic
on anaesthesia
treatment
spinal disorder
(ADHD)
tivity mydriatic
rine),as
nasalsia, heart availablenot is capillary
ture myocardial (ACDE) sia,
O0zing prolong
decongestants labour failure shock, controi to
block,shock,
asthma, Duration
decongestant
(phenyleph due shock
bradycardia
due shock, ephedrine
of (as infarction
or cardiogeric Epistaxis shock,
to hypotension to uterine to cardiac
due of
CCF (phenylephrine) spinal suppress Cardiac
spinal (a, iocal
is
stimulation) relaxant) surgery (M), to when and
with used anaesthe acute shock anaesthe
naesthesia due severe
other arest,
oliguria tofor prema pacing
the to
Hence, ACh isa
Neostigmine "
"Physostigmine
Rivastigmine " Carbamates
Pyridostigmine Choline
esters
CLpAsSeuIFdIoCcAhToIlOinNest(eCraHOLseol gacticIaLquatli.ammoni
oNns.in OMICHeOrnaryLINMEuRmAGEICTEINCTS,
it
has
no
Acetylcholine
Bethanechol
Carbachol
application.
therapeutic
Even
blood.ammonium
in
Directly
acting when
intravenously,
given a
Reversible compound
Edrophonium "
" " Others
Galantamine
Donepezil "
Tacrine
Alkaloids It
Pilocarpine Cholinergic
agonists has
Muscarine
toand
PARASYMPATHOMIMETICS)
be
largegiven is
rapidly
Dyflos
ate "Malathion
"soman, compounds
Sarin,Parathion
" "
gases)Organophosphorus(OP)
(nerve
tabun amount
intravenously
(anticholinesterases)
Indirectly
acting hydrolysed
of
the
drug is to by
Irreversible study
cholinesterases.
Carbamates
Propoxur "
destroyed its
Carbary!
pharma 1.1PH
4
by
