Sympathomimetics Domina Petric, MD

Endogenous catecholamines First chapter Endogenous catecholamines

Adrenaline Adrenaline is agonist of both alfa and beta adrenergic receptors. It is very powerful vasoconstrictor and stimulator of heart. Adrenalin has positive inotropic and chronotropic activity on the heart muscle (predominantly β1-receptors). It activates β2-receptors in sceletal muscles where it stimulates vasodilatation.

NORAdrenaline Noradrenaline is agonist for α1 and α2 receptors. It also stimulates β1 receptors, but less than adrenalin does, and β2 receptors weakly. Noradrenaline increases peripheral resistance, diastolic and systolic blood pressure. It has positive ionotropic and chronotropic effect (baroreceptor´s reflex fights back and tends to lower heart rate).

DOPAMINE It is a precursor for noradrenaline synthesis. It is important for regulation of sodium ions excretion and renal function. It is very important neurotransmitter in central nervous system.

Direct sympathomimetics Second chapter Direct sympathomimetics

phenylephrine It has longer effect than endogenous catecholamines. It is used as mydriatic drug and decongestant. It can also be used to elevate blood pressure.

Midodrine It is a prodrug that hydrolises into deglymidodrine. Deglymidodrine is a selective α1-receptors agonist. Primary indication is treatment of orthostatic hypotension.

A2-selective agonists They act on the central nervous system. Clonidine, methyldopa and others are used to treat arterial hypertension.

Xylometazoline, oxymetazoline They are used as nasal decongestants locally. Oxymetazoline has significant afinity for α2A-receptors.

Isoproterenol It is very potent agonist of β-receptors with little effect on α-receptors. It has positive chronotropic and inotropic effect on the heart. It is powerful vasodilator. Summing effect is significant increase in heart minute volume, decrease in diastolic and mean arterial blood pressure with mild decrease or increase in systolic blood pressure.

Dobutamine Dobutamine is β1-selective medication prepared as racemic mixture. Right isomer is powerful β1-agonist and α1-antagonist, whilst left isomer is powerful α1-agonist. Summing effect is positive inotropic and chronotropic effect and less decrease in peripheral resistance than other similar drugs.

B2-selective agonists These are very important drugs in treatment of asthma and premature labour.

Symathomimetics with mixed effect Third chapter Symathomimetics with mixed effect

ephedrine It has moderate stimulative effect in the central nervous system. Pseudoephedrine is sometime used as nasal decongestant.

Direct sympathomimetics Fourth chapter Direct sympathomimetics

Direct sympathomimetics Amphetamin and similar drugs Inhibiotors of catecholamine reuptake amphetamin metamphetamin phenmetrazine methylphenidate modafinil atomoxetine (ADHD treatment) reboxetine sibutramine (obesity treatment) duloxetine (antidepressant) cocain

Tyramine Katzung, Masters, Trevor. Clinical pharmacology. It is a nusproduct of tyrosine synthesis in the body. It can be found in high concentrations in cheese, sousages, dried fish… Monoamine oxidase (MAO) metabolises tyramine in the liver. Patients who take MAO-inhibitors should avoid tyrosine rich foods because high levels of tyrosine can cause severe arterial hypertension. Katzung, Masters, Trevor. Clinical pharmacology.