Isoprenaline is a type of drug called a beta-agonist that works on the heart to increase the force and rate of the heart beats. This increases the blood pressure and is useful in the short-term treatment of heart block and shock.
It is only available as an injection to be used in a hospital environment and may also be known by the brand name Isuprel.
What is it used for?
Isoprenaline can be used to manage:
- Heart block
- Bradycardia
- Cardiogenic, septic or hypovolemic shock
This is because of the effect it has on the heart to increase the heart rate. It is only used in the short-term in a hospital environment.
How does Isoprenaline work?
Isoprenaline is a type of drug called beta-agonist because it works by activating the beta receptors in the body. When these receptors are activated, the body responds in certain ways, making the heart beat. more quickly.
The amount of the blood that the heart pumps around the body, called the cardiac output, increases because of changes in the heart muscle and action. The cardiac muscles get stronger and are able to pump more blood with each beat and it also pumps more often.
The blood pressure also increases because of the increased volume of blood pumped around the body. Additionally, the smooth muscles surrounding the blood vessels tighten, causing them to become narrower and increase the blood pressure even further.
Side Effects
The side effects of isoprenaline make sense when you think about how the drug works. It is used to increase the heart rate and blood pressure in dangerous situations but if the dose is too high, these effects can be dangerous. Side effects may include:
- Heart palpitations
- Fast heart rate (tachycardia)
- Abnormal blood pressure (hypertension or hypotension)
- Flushing
- Headache
- Nervousness
- Restlessness
- Tremor
For the full list of side effects, you should see the medicine information leaflet.
Precautions
There are some people who shouldn’t take isoprenaline, as it can have worse effects for them. It is not likely to be a good choice if you have phaeochromocytoma, tachycardia, or have recently suffered from a myocardial infarction
Additionally, there are some people who can take isoprenaline, but with extra caution because they are more likely to experience problems. This might be the case if you have:
- Ischaemic Heart Disease (IHD)
- Uncontrolled Hypertension
- Uncontrolled hypovolemia
- Hyperthyroidism
Drug Interactions
There are several drugs that can interact with isoprenaline.
Beta blockers can increase the effect of isoprenaline. This means that side effects will be more likely, particularly difficulty breathing if you suffer from asthma. If a beta blocker is required, a B1 selective drug is preferred such as atenolol, bisoprolol or metoprolol.
Entacapone can reduce the metabolism of isoprenaline. This means that the concentration of the drug will be higher than usual and side effects such as increased heart rate more likely. To manage this interaction, the isoprenaline dose can be reduced.
Theophylline can cause hypokalemia in the body when paired with isoprenaline. Additionally, isoprenaline can reduce the dose of theophylline and you made need a higher dose of theophylline than usual.
Pregnancy and Breastfeeding
Isoprenaline is thought to be safe for use in pregnancy and has been used to treat many women who are pregnant without significant adverse effects.
Likewise, it is thought to be safe for women who are breastfeeding, although there is no data to confirm this.
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