Agonists
Selective
a1
Acute hypotension
-Phenylephrine
-Methoxamine
Chronic postural hypotension
-Midodrine
Nasal congestion
-Phenylephrine
-Xylometazoline
-Oxymetazoline
used with antihistaminics
Eye redness and iritation
-Oxymetazoline
a2
alpha-methyl dopa: antihypertensive
Can cause rare heptotoxicity and autoimmune haemolytic anaemia
Tizanidine: decrease SM spasms
B1
Dopamine: +ve chronotropic, +ve inotropic(Cardiac dose)
Dobutamine: used in cardiac stress tests
may induce chest pain and cardiac arrythmias
B2
Salbutamol: bronchodilation in acute asthma and COPD
Ritodrine: uterine relaxation(tocolytic) in premature labour
Terbutaline: bronchodilator and tocolytic
Non-selective
Adrenaline(Direct):
-Haemostatic
-Anaphylactic shock(SC)
-Cardiac arrest(IV)
combined with anaesethetics:
-increased duration of action
-decreased incision bleeding
-decreased anesethia side effects
Noradrenaline(Direct):
1st choice vasopressor used in septic shock
Pseudophedrine(Direct&Indirect):
with antihistamines treat nasal and sinus congestion(Oral)
Amphetamine(Indirect):
-Euphoria(ABUSE)
-ADHD treatment
-Increased BP
Dopamine
D1 Low dose(renal)(<2μg/kg/min):
improves blood flow to vicera
B1 Intermediate dose(cardiac)(2-10μg/kg/min):
+ve chronotropic, +ve inotropic helps sustain renal function and increases CO
a1 high dose(vascular)(>10μg/kg/min):
Vasoconstriction used in hypovolemic shocks
antagonists
Selective
a
Symptomatic treatment of BPH:
Prazosin
Terazosin(longer 1/2HT)
Tamsulosin>(passage of renal stones)
Migraine:
Ergotamine
Triptan derivatives>
Hypertension (only when other drugs are not effective)
B
Esmolol: short acting
Atenolol & Metoprolol:
treat hypertension
Non-selective
a
Phenoxybenzamine(Irreversible)
Phentolamine
-used preoperation in pheochromocytoma
B
Propranolol: highly lipophilic only 30%
reach systemic circulation it can cross BBB
low dose: tremors and anxiety
Nadolol: Long acting(Less lipophilicity)
Timolol:glucoma
Inhibit lypolysis and glycogenolysis
Combined
Nebivelol: dose-dependent B1 blocker
vasodilation(NO)
Labetalol & Carvedilol:
vasodilation(a1 blockers)
Adverse Reactions:
1- Blockade of cardiac B1: Bradycardia and heart failure.
2- Blockade of B2 (non-selective beta-blockers):
Bronchospasm, Vasoconstriction (cold extremities)
Hypoglycemia with insulin or oral hypoglycemics. Also they mask symptoms of hypoglycemia
3- Sudden stoppage of beta-blockers after regular intake will give rise to a withdrawal syndrome:
tachycardia, rebound angina, arrhythmia, or hypertension.
Therapeutic uses:
1- Hypertension:
•Heart: reducing the cardiac output (B1).
•Kidney: reducing renin and aldosterone secretion (B1).
•Presynaptic B2 receptors: will decrease noradrenaline release from adrenergic nerve terminals.
2- Angina pectoris: in stable angina through reduction of HR, BP and contractility thus decreasing O2 demand during rest and exercise.
3- Cardiac arrhythmias: treatment of both supraventricular and ventricular arrhythmias by slowing AV conduction.
4- Chronic heart failure: e.g. carvedilol, metoprolol, and
bisoprolol. (Reduce mortality)
5- Hyperthyroidism: Propranolol especially; by blocking sympathetic overstimulation inhibit conversion T4 into T3
6-propyllaxis of migraine headache: Propranolol in between attacks
7- Pheochromocylome with alpha blockers.
(4)Contraindicated in acute heart failure
Adverse reactions:
-Postural hypotension
Side effect:
1.↑ BP:headache
2. Chest pain, difficulty of breathing, and feelings of nervousnes.
3-Topical nasal decongestants:
-Stinging, burning, and drying of the nostrils.
-Atrophy of the cilia of the nasal mucosa with↑susceptibility to
infection and loss of sense of smell.
-Rebound nasal congestion upon withdrawal. That's why intranasal
formulations of a1-agonists should be used no longer than 3days
Side effects:
-Nervousness(stimulation of central B receptors)
-Skeletal muscle tremors and tachycardia
-Ritodrine causes increase in maternal heart rate and BP
-The long-term use may induce hypokalaemia and tolerance.
Side effects:
-Anxiety, fear, tremors
-Arrythmias, cardiac arrest
-Cerebral haemorrhage(high BP)
-High doses: psychosis & convulsions
-Chronic doses: Tolerance