Difference between revisions of "Isoprenaline"

Latest revision as of 15:49, 19 September 2010

Isoprenaline (INN) or isoproterenol (USAN, trade names Medihaler-Iso and Isuprel) is a sympathomimetic beta adrenergic agonist medication.

It is structurally similar to adrenaline. Isoproterenol is a β1 β2 non selective agonist. ^[1]

Uses

Its primary use is for bradycardia or heart block. By activating β₁-receptors on the heart, it induces positive chronotropic, dromotropic, and inotropic effects.^[1]

It can be used as an inhaled aerosol to treat asthma, although this is currently a rare treatment.^[1] Although it activates all beta adrenergic receptors, it works in a similar fashion to the more selective β₂-adrenergic agonists e.g. salbutamol, by relaxing the airways to increase airflow.

It is also supplied in ampules under the brand name Isuprel for injection and in sublingual pill form for treatment of asthma, chronic bronchitis and emphysema.

Used with caution, it can also be used to treat torsades de pointes by acquired defect, in conjunction with overdrive pacing and magnesium.

Pharmacology

Isoprenaline is a β₁- and β₂-adrenoceptor agonist which was commonly used to treat asthma before the more widespread use of salbutamol, which has more selective effects on the airways. Its route of administration is either intravenous, oral, intranasal, subcutaneous, or intramuscular, depending on use. The plasma half-life for isoprenaline is approximately two hours.

Isoprenaline's effects on the cardiovascular system(non-selective )relate to its actions on cardiac β₁ receptors and β₂ receptors on skeletal muscle arterioles. Isoprenaline has positive inotropic and chronotropic effects on the heart. In skeletal muscle arterioles it produces vasodilatation. Its inotropic and chronotropic effects elevate systolic blood pressure, while its vasodilatory effects tend to lower diastolic blood pressure.

The adverse effects of isoprenaline are also related to the drug's cardiovascular effects. Isoprenaline can produce an elevated heart rate (tachycardia), which predisposes patients to cardiac dysrhythmias. According to Code of Federal Regulations (CFR) Title 21 Section 201.305; use of isoprenaline has been regulated by mandating the inclusion of the following warning label: "Occasional patients have been reported to develop severe paradoxical airway resistance with repeated, excessive use of isoproterenol inhalation preparations. The cause of this refractory state is unknown. It is advisable that in such instances the use of this preparation be discontinued immediately and alternative therapy instituted, since in the reported cases the patients did not respond to other forms of therapy until the drug was withdrawn. Deaths have been reported following excessive use of isoproterenol inhalation preparations and the exact cause is unknown. Cardiac arrest was noted in several instances"

Warnings and contraindications

Isoprenaline should not be administered to patients with myocardial ischemia.

References

de:Isoprenalin es:Isoproterenol fa:ایزوپروترنول fr:Isoprotérénol it:Isoprotenerolo ja:イソプロテレノール pt:Isoproterenol

1. ↑ ^{1.0 1.1 1.2} Shen, Howard (2008). Illustrated Pharmacology Memory Cards: PharMnemonics. Minireview. p. 5. ISBN 1-59541-101-1.