CHOLINOCEPTORACTIVATING & CHOLINESTERASEINHIBITING DRUGS Flashcards
Mimic acetylcholine
CHOLINOMIMETIC DRUGS
TYPE OF CHOLINOMIMETIC DRUGS Classified by
A. Spectrum of action (type of receptor activated)
- Muscarinic
2. Nicotinic
TYPE OF CHOLINOMIMETIC DRUGS Classified by
B. Mechanism of action
1. Direct-acting Binding/activate cholinoceptors 2. Indirect-acting Inhibiting the hydrolysis of endogenous ACh
CHOLINOMIMETIC DRUGS
Divided on the basis of their chemical structure
Directly bind to and activate muscarinic or
nicotinic receptors
Many have effects on receptors like ACh
A. DIRECT-ACTING CHOLINOMIMETIC DRUGS
BASIC PHARMACOLOGY OF THE DIRECT ACTING CHOLINOCEPTOR STIMULANTS (2)
- CHOLINE ESTERS
Including ACh - ALKALOIDS
Muscarine and nicotine
BASIC PHARMACOLOGY OF THE DIRECT ACTING CHOLINOCEPTOR STIMULANTS
4 important choline esters
Permanently charged quaternary NH 4 group
Relatively insoluble in lipids
CHOLINE ESTERS
BASIC PHARMACOLOGY OF THE DIRECT ACTING CHOLINOCEPTOR STIMULANTS
Poorly absorbed
Poorly distributed in the CNS
Hydrophilic
CHOLINE ESTERS
BASIC PHARMACOLOGY OF THE DIRECT ACTING CHOLINOCEPTOR STIMULANTS
Hydrolyzed in the GIT
Differ markedly in their susceptibility to
hydrolysis by cholinesterase
CHOLINE ESTERS
BASIC PHARMACOLOGY OF THE DIRECT-ACTING
CHOLINOCEPTOR STIMULANTS
Very rapidly hydrolyzed
Large amounts must be infused IV to achieve
concentrations high enough to produce
detectable effects
ACETYLCHOLINE
BASIC PHARMACOLOGY OF THE DIRECT-ACTING
CHOLINOCEPTOR STIMULANTS
Addition of methyl CH3
3x more resistant to hydrolysis compared to ACh
METHACHOLINE
BASIC PHARMACOLOGY OF THE DIRECT-ACTING
CHOLINOCEPTOR STIMULANTS
Carbamic acid ester derivative of ACh
More resistant to hydrolysis by cholinesterase
Longer duration of effect
CARBACHOL and BETANECHOL
BASIC PHARMACOLOGY OF THE DIRECT-ACTING
CHOLINOCEPTOR STIMULANTS
Addition of beta-methyl group (methacholine and
betanechol reduces the potency of these drugs at
nicotinic receptor sites
CARBACHOL and BETANECHOL
BASIC PHARMACOLOGY OF THE DIRECT-ACTING
CHOLINOCEPTOR STIMULANT
Act mostly with muscarinic receptors
(muscarine, pilocarpine)
Act with nicotinic receptors
(nicotine, lobeline)
- ALKALOIDS
BASIC PHARMACOLOGY OF THE DIRECT-ACTING
CHOLINOCEPTOR STIMULANT
Well absorbed from most sites of administration
Excreted chiefly by the kidneys
Acidification of urine accelerates clearance of
these amines
- ALKALOIDS
BASIC PHARMACOLOGY OF THE DIRECT-ACTING
CHOLINOCEPTOR STIMULANT
Liquid
Sufficiently lipid-soluble to be absorbed across
the skin
NICOTINE
BASIC PHARMACOLOGY OF THE DIRECT-ACTING
CHOLINOCEPTOR STIMULANT
Quaternary amine
Less completely absorbed from the GIT
Toxic when ingested
Eg, in certain mushrooms, it even enters the brain
MUSCARINE
BASIC PHARMACOLOGY OF THE DIRECT-ACTING
CHOLINOCEPTOR STIMULANT
Plant derivative
Similar to nicotine
LOBELINE
ORGAN SYTEM EFFECTS
Instilled to the conjunctival sac Causes contraction of the sphincter muscle of iris (miosis) Causes ciliary muscle contraction (accommodation)
- EYE
ORGAN SYTEM EFFECTS
Reduction in peripheral resistance and
changes in heart rate
- CVS
ORGAN SYTEM EFFECTS
Contraction of the smooth muscles of the
bronchial tree
Stimulate glands of the tracheobronchial
mucosa to secrete
- RESPIRATORY SYSTEM
ORGAN SYTEM EFFECTS
Similar to the parasympathetic nervous
system stimulation
Increase in the secretory and motor activity
of the gut
- GIT
ORGAN SYTEM EFFECTS
Stimulation of the salivary and gastric glands
Increase in peristaltic activity
Relaxation of sphincters
- GIT
ORGAN SYTEM EFFECTS
Endothelium Derived Relaxing Factor (EDRF) is released to produce dilation Dilation of arteries Dilation of veins Constriction (high-dose direct effect)
- BLOOD VESSELS
ORGAN SYTEM EFFECTS
Stimulate the detrussor muscle
Relax the trigone and sphincter
Promote voiding
- GUT
ORGAN SYTEM EFFECTS
Stimulate the thermoregulatory sweat,
lacrimal and nasopharyngeal glands
- GLANDS
CHOLINOMIMETIC DRUGS
Primary effect by inhibiting acetylcholinesterase
which hydrolyzes acetylcholine to choline and
acetic acid
B. INDIRECT-ACTING CHOLINOMIMETIC DRUGS
CHOLINOMIMETIC DRUGS
Increase endogenous ACh concentration
Stimulates cholinoceptors to evoke increase
response
B. INDIRECT-ACTING CHOLINOMIMETIC DRUGS
CHOLINOMIMETIC DRUGS
Parasympathetic effects
Some have direct action at nicotinic receptors
B. INDIRECT-ACTING CHOLINOMIMETIC DRUGS
CHOLINOMIMETIC DRUGS
Chief difference of the group are chemical and
pharmacokinetics
3 chemical groups
B. INDIRECT-ACTING CHOLINOMIMETIC DRUGS
BASIC PHARMACOLOGY 0F INDIRECT-ACTING
CHOLINOMIMETICS
Quaternary NH4 group
2 to10 minutes
Reversible
- SIMPLE ALCOHOLS
BASIC PHARMACOLOGY 0F INDIRECT-ACTING
CHOLINOMIMETICS
Quaternary or tertiary NH4 group
30 minutes to 6 hours
Reversible
- CARBAMIC ACID ESTERS OF ALCOHOL
BASIC PHARMACOLOGY 0F INDIRECT-ACTING
CHOLINOMIMETICS
Highly lipid soluble
Very long duration
Irreversible
- ORGANIC DERIVATIVES OF PHOSPHORIC
ACID
BASIC PHARMACOLOGY 0F INDIRECT-ACTING
CHOLINOMIMETICS
Echothiophate
-Retains the very long duration of other
organophosphates
-More stable in aqueous solution
- ORGANIC DERIVATIVES OF PHOSPHORIC
ACID
ORGANIC DERIVATIVES OF PHOSPHORIC
ACID
Used as insecticides
Parathion and malathion (thiophosphates)
Primary action is to amplify the actions
of endogenous Ach
Effects are similar, but not always identical,
to the effects of direct-acting cholinomimetics
ORGAN SYSTEM EFFECTS
ORGAN SYSTEM EFFECTS
Most prominent effects
CVS
GIT
Eye
Skeletal muscle neuromuscular junction
CLINICAL PHARMACOLOGY OF CHOLINOMIMETICS
Pilocarpine Echothiophate (long-acting effect)
- EYE
CLINICAL PHARMACOLOGY OF CHOLINOMIMETICS
POSTOPERATIVE ILEUS
URINARY RETENTION POST OP
- GIT and GUT
- GIT and GUT
Clinical disorders that involve depression of smooth muscle activity without obstruction
Betanechol
CLINICAL PHARMACOLOGY OF
CHOLINOMIMETICS
NEUROMUSCULAR JUNCTION
Disease affecting the skeletal muscles
neuromuscular junction
Autoimmune process
MYASTHENIA GRAVIS
NEUROMUSCULAR JUNCTION Production of antibodies that decrease the functional nicotinic receptors at the postjunctional end plates Cholinesterase inhibitors are used for therapy
MYASTHENIA GRAVIS
MYASTHENIA GRAVIS
diagnostic test
Edrophonium
MYASTHENIA GRAVIS
long term therapy
Neostigmine, pyridostigmine
CLINICAL PHARMACOLOGY OF
CHOLINOMIMETICS
SUPRAVENTRICULAR TACHYCARDIA
Treated by short-acting cholinesterase inhibitor
(edrophonium)
Replaced by newer drugs (calcium channel
blockers)
- HEART
- ANTIMUSCARINIC DRUG INTOXICATION
Lethal in children
Causes prolonged severe behavioral
disturbances and arrhythmias in adults
ATROPINE INTOXICATION
- ANTIMUSCARINIC DRUG INTOXICATION
Causes severe muscarinic blockade
Physostigmine
Antidote to atropine poisoning
ATROPINE INTOXICATION
CNS ALZHEIMER’S DISEASE With anticholinesterase activity With cholinomimetic action Used for therapy
Tacrine
TOXICITY
A. DIRECT-ACTING MUSCARINIC STIMULANTS
Nausea and vomiting Diarrhea Salivation Sweating Cutaneous vasodilatation Bronchial constriction Excitation Lacrimation
A. DIRECT-ACTING MUSCARINIC STIMULANTS
BLOCKED BY
atropine
DIRECT-ACTING NICOTINIC STIMULANTS
40 mg or 1 drop of pure liquid is fatal
2 cigarettes
Central stimulant action
ACUTE TOXICITY
DIRECT-ACTING NICOTINIC STIMULANTS
Convulsion Coma Respiratory arrest or paralysis Hypertension Arrhythmia
ACUTE TOXICITY
DIRECT-ACTING NICOTINIC STIMULANTS
Treatment is symptom directed
Atropine
Anticonvulsants
ACUTE TOXICITY
DIRECT-ACTING NICOTINIC STIMULANTS
Smoking
CHRONIC TOXICITY
RISK OF chronic toxicity increased when
Vascular disease
Peptic ulcers
60 % carcinogenic
C. CHOLINESTERASE INHIBITORS
Major source of intoxication is pesticid
Organophosphates
Treated with large doses of atropine
ACUTE TOXICITY