What is Mephenteramine can be used in hypovolemic shock, although intravenous fluid supplementation is primary treatment. It acts by and explain in detail?
Ans. d (All of the above) (Ref. KDT 5th/pg. 114)SYMPATHOMIMETICSCatecholaminesNoncatecholaminesAdrenalineEphedrineNoradrenalinePhenylephrineIsoprenalineMetaraminolDopamineMethoxamineDobutamine Dopexamine Selective b2-receptor agonists (salbutamol, terbutaline, ritodrine, metaproterenol, fenoterol and orciprenaline)Other Sympathomimetic Amines (amphetamine, methamphetamine, mephentermine and some newer agents like Prenalterol,Pirbuterol, Xamaterol, fenoldopam, etc)PrenalterolIt is a relatively selective pi agonist that has been used in the management of CHF.It is also useful orally, with a bioavailability of about 33%.PirbuterolIt a b2 agonist which has been used both as a bronchodilator and as an inotrope.XamaterolIt is an orally active partial b1 agonist used for chronic CHFDopamine analogsAside from dopexamine other dopamine analogs have been used in Rx of CHF and HTN.MEPHENTERMINEMechanism of action# Indirectly stimulates beta adrenergic receptors and possibly to a lesser extent alpha adrenergic receptors.# The main effect of therapeutic doses of mephentermine is cardiac stimulation .# Force of contraction and CO are usually increased, accompanied by an increased stroke volume.# Mephentermine shortens atrioventricular (AV) conduction velocity and the refractory period of the AV node and increases ventricular conduction velocity.# Heart rate may be increased, decreased or unchanged.# Mephentermine increases the coronary blood flow, but the work of the heart and myocardial consumption are correspondingly increased.# Mephentermine directly dilates the arteries and arterioles in the skeletal and mesenteric vascular beds.# Venous return to the heart is increased in patients receiving mephentermine.# The drug usually increases systolic and diastolic blood pressure by increasing cardiac output; increases in cardiac output are greatest when initial cardiac output is low. When initial cardiac output is high, increased total peripheral resistance may be responsible for increase in blood pressure.# Mephentermine also dilates the coronary, cerebral, splanchnic and renal blood vessels.# It stimulates the central nervous system and may cause anxiety, seizures or tachycardia.Indications# Shock accompanying myocardial infarction. Injection mephentermine is favoured in combating hypotensive states in cardiogenic shock.# Hypotension occurring during surgical procedures or following spinal anesthesia.# Prevention of hypotension attendant to spinal anesthesia to surgical procedures or occurring in recovery.Contraindications# Injection mephentine is not advocated for the treatment of hypotension caused by phenothiazines.# When shock is primarily due to loss of blood or fluid the primary consideration in treatment should be the replacement of circulating blood volume. The use of mephentine alone is not advocated in such conditions.