Organic nitrate acts on venous capacitance.
Route of administration
Tablets- oral , buccal , transmucosal , lingual spray.
Transdermal patch or ointment – 5 to 10mg.
Over 24 hours provides sustained protection against myocardial ischaemia.
Mechanism of action
Generates NO with acts as mediator resulting in peripheral vasodilators in presence of two containing compounds
- t1[half life]/21.5min
- large volume of distribution
- Nitrate metabolite of NTG is capable of oxidizing the ferrous ion in Hb to the ferric state with the production of methhemoglobin .
Effects on organ systems
CVS: Doses up to 2 mcg/kg/min IV ➔ dilatation of veins ➔ venous return and decrease LVEDP[Ltventricular diastolic presssure] and RVEDP.[Rt.ventricular end diastolic pressure]
Heart rate increases slightly.
NTG reduces systemic blood pressure depend more on blood volume than do blood pressure changes like SNP[sodium nitroprusside]
Sublingual administration causes markedly hypotension , excessive decrease in diastolic blood pressure may decrease coronary blood flow
This may also evoke baroreceptor mediated reflex increase in sympathetic nervous activity ➔ tachycardia and increased myocardial contractility combination of decrease coronary blood flow and increase myocardial O2 requirement may provoke angina pectoris in susceptible patients
SVR isnot affected
PVR is decreased
NTG primarily dilates coronary arteries often leading to an increase in coronary blood to ischemic subendocardial areas
Recommended for treatment of hypertension in patients with coronary artery disease
Sublingual 0.3mg – not recommended now.
APPLICATION OF 2% NTG ointment over a skin area of 2.585 produces sustained protection from angina pectoris for upto 4 hours
Mechanism of Action
Selectively dilates large coronary arteries may be an important mechanism of relief of angina pectoris due to vasosapam. It redistributes the coronary blood flow to ischaemic areas of subendocardium by dilating epicardial vessels
Decrease venous return —-decrease LVEDP and RVEDP and ➔ myocardial oxygen requirements
Headache becoz of dilatation of meningeal vessels , vascular dilatation in face and neck manifest as facial flushing.
Decrease preload and relieves pulmonary oedema.
Inflation of NTG to patients with acute MI can improve Cardiac output . Relieve pulomonary congestion and decrease myocardial O2 requirement.
ISOSORBIDE DI NITRATE
Oral nitarte for prophylaxis of angina pectoris.
60-120mg for 6hours.
Metabolite of isosorbide di nitrate ➔ isosorbide 5-mononitrate is more active.
Side efect: orthostatic hypotension.
Is prescribed with warfarin as prophylaxis against thromboembolism and to inhibit platelet aggregation
Smooth muscle relaxant by inhibiting phosphodiesterase increases intracellular concentration of cAMP.
Peripheral vasodilator and ganglionic blocker.
Action is rapid so to be given in infiltration.
Lowers systemic BP by decrease CO and SVR . It blocks ANS reflexes.
Ganglionic blockade ➔ mydriasis, decrease GIT including ileus and urinary retention.
Benzothiadiazene derivative related to thiazide diuretics
IV- 1-3 mg/kg upto 150mg ➔ decreases systolic and diastolic BP for 6-7 hrs
Excretion:kidneys t1/2-28 hrs
Side effects: water retention so patient have CCfF
Formed by product of enzymatic breakdown of either adenosine triposphate or s – adenosyl homocu=ysteine
Potent dilator of coronary arteries and is capable of decrease myocardial O2 consumption by its anti adrenergic effect and negative chronotropic action
T1/2 is 0.6-1.5 sec bcoz of its deamination to inosine in plasma and its uptake by erythrocytes
Principle electrophysiologic actions of adenosine on supraventricular tisues SA node and atrium are mediated by stimulation of K+ channels
Hyper polarization of atrial myocytes and decrease in diastolic depolarization of pace maker cells of SA mode
Ventricular myocytes donot have these adenosine – same as K+channels
- Treat PSVT
- Control HTN by decreasing SVR
- Alternative to dypyridamole for pharmacologic stress testing
- SVT:atrial orjunctional tachycardia 6mg IV followed by 12 mg IV – 18mg IV if well tolerated by the patient
- Children : 0.2mg/kg
Not effective in treatment of Atrial flutter , Atrial Fibrillation and ventricular tachycardia.
Adenosine in awkae patients: dyspnea ,flushing , chest pain and broncho spasm.