Sympatholytics (Antiadrenergic Agents) 149It is rapidly absorbed after oral
administration with 40% bioavailability. It
is metabolised in liver by cytochrome P450
to a less active metabolite which is
predominantly excreted in faeces (80%) and
in urine (13%).
It is useful in erectile dysfunction of any
etiology.
Adverse effects include headache,
flushing, dyspepsia, nasal congestion,
abnormal vision (mild and transient),
diarrhoea, dizziness, angina pectoris, AV
block, palpitation, postural hypotension,
priapism etc.
Dose: VIAGRA; 25-100 mg/day.
The newer drug of same category are
alprostadil, vardenafil and tadalafil which
are recently introduced for erectile
dysfunction in man. Apomorphine is
recently introduced for erectile dysfunction
with proven efficacy and safety, given
sublingually and acts within 20 minutes in
a dose of 2-3 mg.BETA ADRENERGIC BLOCKERSThese are the agents which block the action
of sympathetic nerve stimulation and
circulating sympathomimetic amines on the
beta adrenergic receptors. At the cellular
level, they inhibit the activity of the
membrane cAMP. The main effect is to
reduce cardiac activity by diminishing β 1
receptor stimulation in the heart. This
decreases the rate and force of myocardial
contraction of the heart, and decreases the
rate of conduction of impulses through the
conduction system. They are classified as in
table 3.3.2.Table 3.3.2: Classification for beta adrenergic blocking agents.
A.Non-selective (βββββ 1 +βββββ 2 )
Propranolol (CIPLAR) 10-80 mg TDS, 2-8 mg IV
Sotalol (SOTAGARD) 80-480 mg/day
Nadolol 40-240 mg OD
Timolol (TIMOPRESS) 5-20 mg BD, 0.25-0.5% topical (eye)
Alprenolol 200-800 mg/day
Pindolol (VISKEN) 10-30 mg/day
With additional alpha blocking activity
Labetalol (LOBATE) 100-200 mg TDS, 50 mg IV
Carvedilol (CARDIVAS) 12.5-50 mg BD
B.βββββ 1 Selective (cardioselective)
Metoprolol (BETALOC) 100-450 mg/day
Atenolol (BETACARD) 50-100 mg/day
Bisoprolol (CONCOR) 5 mg OD-BD
Celiprolol (CELIPRESS) 100-200 mg/day
C.βββββ 2 Selective
Butoxamine