Review of Pharmacology - 9E (2015)

Autonomic Nervous System
• Dopamine is the drug of choice for cardiogenic shock with oliguric renal failure. It acts on
D 1
(at a dose of 1-2 µg/kg/min.), β 1
(at 2-10 µg/kg/min.) and α 1
(at > 10 µg/kg/min.)
receptors. It causes renal vasodilation by acting on D 1
receptors and maintains renal
perfusion and GFR. Other ionotropic agents like NA cause renal vasoconstriction
and thus worsen renal failure.
• Ibopamine has similar properties as DA.
• Dobutamine is relatively selective β 1
agonist with no action on DA receptors. It
increases cardiac output with little action on heart rate.
• Dopexamine combines β 2
and D 1
agonistic activity with NA reuptake inhibitory action.
• Fenoldopam is D 1
agonist useful in hypertensive emergencies.
Concentration of adrenaline for different routes and indications
Route and Indication
Bronchial asthma, inhalational 1:100
Anaphylactic shock, intramuscular 1:1000
Anaphylactic shock, subcutaneous 1:1000
Anaphylactic shock, intravenous 1:10000
Cardiac arrest, intravenous 1:1000
With Local anaesthetics, subcutaneous 1:200000
Concentration of Adrenaline required
Uses of clonidine:
• Hypertension
• To control diarrhea in diabetic
patients with autonomic
neuropathy.
• Prophylaxis of migraine.
• Management of withdrawal
symptoms of alcohol, nicotine
and opioids.
• Epidurally, in combination
with opioids for relief of pain.
• For treatment of ADHD [as
monotherapy or adjunctive to
other drugs]
N
Mirabegron is a new drug
approved for overactive bladder.
It acts by stimulating b 3
receptors
Non Catecholamines
α 1
agonists: These drugs can be used as nasal decongestants like naphazoline, oxymetazoline
and xylometazoline. When effect of these drugs subside, after-congestion is seen. If used for
prolonged periods, these can result in atrophic rhinitis (Rhinitis medicamentosa). Phenylephrine
can also be used as a mydriatic (does not cause cycloplegia). Methoxamine and mephentermine
can be used to inrease BP in hypotensive states. Midodrine is a prodrug (active metabolite is
desglymidodrine) used for the treatment of orthostatic hypotension.
• Phenylpropanolamine was banned due to risk of hemorrhagic stroke
α 2
agonists: Clonidine and α methyldopa (a prodrug) are α 2
agonists that can be used for the
treatment of hypertension. Other uses of clonidine include:
• To control diarrhea in diabetic patients with autonomic neuropathy.
• Prophylaxis of migraine.
• Management of withdrawal symptoms of alcohol, nicotine and opioids.
• Epidurally, in combination with opioids for relief of pain.
• For treatment of ADHD [as monotherapy or adjunctive to other drugs]
Apraclonidine and brimonidine are selective α 2
agonists used topically for the treatment of
glaucoma. Dexmeditomidine (central α 2
agonist) is used for pre-anaesthetic medication. It is
also indicated for sedation of initially intubated and mechanically ventilated patients during
treatment in ICU. Guanfacine and guanabenz are α 2
agonists similar to clonidine and are
rarely used now. Tizanidine is used as a muscle relaxant.
β 1
agonists: Prenaltrenol is the only non-catecholamine β 1
selective agent. It has been promoted
recently for the reversal of β blockade.
β 2
agonists: Salbutamol (albuterol), levalbuterol, bitolterol, fenoterol, metaproterenol, terbutaline,
pirbuterol, salmeterol, formoterol, arformoterol, carmoterol and indacterol are selective β 2
agonists
useful in bronchial asthma. Ritodrine and isoxsuprine are agonists useful as tocolytic (uterine
relaxant) agents.
β 3
agonists: Mirabegron is a new drug that acts by stimulating b 3
receptors in urinary bladder.
It is indicated for treatment of overactive bladder.
Modafinil is approved for
treatment of
• Narcolepsy,
• In shift workers
• To relieve fatigue in multiple
sclerosis
• An adjunt in obstrutive sleep
apnea.
Ephedrine is the vasopressor of
choice in pregnancy
Autonomic General Pharmacology
Nervous System
69
https://kat.cr/user/Blink99/