SYMPATHOMIMETICS
Prepared by
R.Prem sai
Narayana pharmacy college
Drugs that bind to the adrenergic receptors
and results in activation of adrenergic
receptors are known as
‘’SYMPATHOMIMETICS or ADRENERGIC
AGONISTS’’
SYMPATHOMIMETICS
DIRECT ACTING MIXED ACTING INDIRECT ACTING
Alpha agonists 1-Ephedrine 1-Releasing agents
1-non selective 2-Metaraminol - Amphetamine
a) Epinephrine 2- monoamine oxidase
b) Nor epinephrine inhibitors
2-selective - selegiline
a) Alpha-1 agonists : phenylephrine 3- catechol-o-methyl
b) Alpha-2 agonists : clonidine transferase inhibitors
Beta agonists -Entacapone
1-non selective : Isoproterenol , epinephrine
2- selective
a) Beta -1 agonists : Dopamine
b) Beta -2 agonists : salbutamol , terbutaline
DIRECT ACTING
1-EPINEPHRINE
❖ Epinephrine is one of the four catecholamines commonly used in the
therapy
❖ It is a naturally occurring neurotransmitter
❖ In adrenal medulla , nor epinephrine is methylated to give epinephrine
❖ It interacts with both alpha and beta receptors
❖ It’s interaction depends on dose
At low doses beta effects are strongest
At high doses alpha effects are strongest
PHARMACOLOGICAL ACTIONS
1-Cardiovascular :
❖ It has both positive inotrope and chronotrope activity on heart
as a result cardiac output increases and it also acts on kidneys to
release renin which is a potent vasoconstrictor [beta-1 action]
❖ It also have alpha effects like constriction of arterioles in the
viscera and mucuous membranes and have beta-2 effects like
dilation of vessels in liver and skeletal muscles
2-Respiratory : Epinephrine is a potent bronchodilatior [beta-2
action]
3-Hyperglycemia : This effect is due to increased glycogenolysis in
liver and increase release of glucagon
USES
❖ It is the primary drug used in treatment of anaphylactic shock
and type-1 hypersensitivity reactions
❖ Used to induce and maintain mydriasis during intraocular surgery
❖ It also increases the duration of the local anesthesia
PHARMACOKINETICS
❖ ABSORPTION – Has rapid onset but brief duration of action and
epinephrine is given as IM , IV or SC
❖ METABOLISM – By monoamine oxidase [MAO] and catechol-o-
methyl transferase [COMT]
❖ EXCRETION – metabolites like metanephrine and vanillyl mandelic
acid are excreted by urine
ADVERSE EFFECTS
❖ Epinephrine can cause adverse CNS effects like anxiety , tension
tremors and headache
❖ Can trigger cardiac arrythmias
❖ Also induce pulmonary edema due to increased afterload
2-NOREPINEPHRINE
❖ When given at therapeutic doses alpha receptor is mostly effected
PHARMACOLOGICAL ACTIONS
cardiovascular actions
❖ Causes a rise in peripheral resistance due to vasoconstriction and
also increase systolic and diastolic bloodpressure
❖ Its ability of vasoconstriction is greater than epinephrine as it has
weak beta-2 activity
Baroreceptor reflex
❖ It rises blood pressure stimulates baroreceptors which increase vagal
activity and produces reflex bradycardia
USES
❖ Used to treat shock like septic shock
❖ It has no other significant uses
PHARMACOKINETICS
❖ A – given as IV
❖ M – by MAO and COMT
❖ E – inactive metabolites excreted by urine
ADVERSE EFFECTS
❖ Similar to epinephrine
❖ Blanching and sloughing of skin and cause tissue necrosis if
extravastation occurs
3-DOPAMINE
❖ It is the metabolic precursor of nor epinephrine that mainly occurs
naturally in the basal ganglia of CNS
❖ It acts on both alpha and beta receptors and also on D1 and D2
receptors present in peripheral mesenteric and renal vascular beds
PHARMACOLOGICAL ACTIONS
1- cardiovascular actions
❖ It has stimulatory effects on β1 receptors on heart that increases
both heart rate and contraction of heart and at high doses it cause
vasoconstriction
2-Renal and visceral
❖ Causes dilation of renal and splanchnic arterioles and increase blood
flow to kidneys
USES
❖ Used to treat both cardiogenic and septic shock
❖ Enhances perfusion to both kidney and splanchnic areas
❖ Used to treat hypotension , heart failure , bradycardia
❖ Used to treat acute renal failure [effects are limited]
ADRs
❖ Rapidly metabolized by MAO and COMT so its adverse effects like
nausea , hypertension and arrhythmias are short lived
. DRUG RECEPTORS CLINICAL ADVERSE
USES EFFECTS
Isoproterenol β1and β2 Treat Heart Tachycardia
block and and
cardiac arrest arryhythmias
Sabutamlol,terbut Only β2 Treat Respiratory Tremors ,
aline ,salmeterol disorders like Tachycardia and
and formoterol asthma and COPD hypokalemia
Phenylephrine , only alpha1 Used as Nasal Hypertension and
methoxamine decongestant and anxiety
mydriatic
Clonidine only alpha 2 Treat constipation and
Hypertension xerostomia
INDIRECT ACTING
DRUG ACTION CLINICAL ADVERSE
USES EFFECTS
Amphetamine Both α1 and β1 Treat Attention Nausea , vomiting
and increase defecit and diarrhoea ,
release of hyperactivity circulatory
dopamine and nor disorder and collapse,
epinephrine narcolepsy confusions and
Tremor
Methylphenidate Increase release of Same as Anorexia , fever and
dopamine and it may increase
Amphetamine seizure frequency in
norepinephrine in
epilepsy patients
synaptic cleft
MIXED ACTING
DRUG ACTION CLINICAL ADVERSE
USES EFFECTS
Ephedrine Binds to both α Previously used as Insomnia ,
and β receptors asthma but it is hypertension ,
slow acting and
and enhance also used in
Tachycardia
release of nor anesthesia and
epinephrine induced palpitations
hypotension
Mephentermine Binds to α1 Used in Anxiety , reflex
receptors and treatment of bradycardia and
releases nor hypotensive dyspnea
epinephrine states
