Indoblok contains propranolol 10 mg, a beta blocker. It treats high blood pressure, angina, irregular heart rhythms, essential tremor and an overactive thyroid, and it prevents migraine. It is also used for the physical symptoms of anxiety. It must not be stopped abruptly.
What is Indoblok?
Indoblok contains propranolol, commonly as 10 mg and 40 mg tablets. It is a Schedule 3 medicine, also sold as Inderal and Purbloka.
Propranolol is a non-selective beta blocker. Adrenaline and noradrenaline act on beta receptors throughout the body; propranolol blocks them. The heart beats more slowly and with less force, blood pressure falls, and the physical effects of adrenaline — pounding heart, tremor, sweating — are damped.
“Non-selective” matters. Newer beta blockers such as atenolol and bisoprolol act mainly on beta-1 receptors in the heart. Propranolol blocks beta-2 receptors as well — in the lungs, blood vessels and elsewhere.
That gives it a wider range of uses, because those beta-2 effects are useful for tremor, migraine and thyroid symptoms. It also means it can narrow the airways, which is why it is avoided in asthma.
Propranolol also crosses into the brain more than most beta blockers, contributing to its effect in migraine prevention and anxiety — and to more vivid dreams and fatigue.
What is Indoblok commonly used for?
- High blood pressure, though newer agents are usually preferred first.
- Angina, reducing how often episodes occur.
- Irregular heart rhythms, including atrial fibrillation and some fast rhythms.
- After a heart attack, to reduce further events.
- Migraine prevention — a well-established use, taken daily to reduce attack frequency.
- Essential tremor, where it is a first-line treatment.
- Overactive thyroid (thyrotoxicosis), to control palpitations and tremor while definitive treatment takes effect.
- Performance and situational anxiety, for the physical symptoms.
- Portal hypertension, to reduce variceal bleeding risk in liver disease.
The anxiety use is worth explaining, because it is often misunderstood. Propranolol does not treat anxiety itself — it blocks the physical manifestations: the racing heart, trembling hands, shaky voice and sweating. For someone whose anxiety is driven by those bodily symptoms feeding back into their fear, breaking that loop helps considerably.
But it does nothing for the psychological experience, and it is not a treatment for an anxiety disorder. For that, cognitive behavioural therapy and, where medication is needed, an SSRI are the appropriate tools.
For migraine prevention, it is taken every day, not during an attack, and it takes several weeks to show benefit. It reduces how often attacks happen rather than treating one in progress.
How Indoblok fits into this medicine category
| Group | Examples | Note |
|---|---|---|
| Non-selective beta blockers | Propranolol (Indoblok) | Broad uses; avoided in asthma |
| Cardioselective beta blockers | Atenolol, bisoprolol, metoprolol | Mainly cardiac; safer in lung disease |
| Calcium channel blockers | Amlodipine | Blood pressure, angina |
| ACE inhibitors / ARBs | Enalapril, losartan | Blood pressure, heart failure |
| Diuretics | Hydrochlorothiazide (Ridaq) | Blood pressure and fluid |
See the heart, blood pressure and circulation medicines hub.
What to check before using Indoblok
Never stop it abruptly. This is the most important caution. Suddenly stopping a beta blocker causes rebound — a surge in heart rate and blood pressure that can trigger angina, a heart attack or a dangerous rhythm, particularly in someone with heart disease. Any change is tapered over one to two weeks under medical guidance.
Take it at consistent times, and do not run out.
Tell your prescriber or pharmacist if you:
- Have asthma or COPD. Propranolol can cause serious bronchospasm and is generally avoided in asthma — this is the key contraindication.
- Have a slow heart rate or a heart block.
- Have heart failure that is not stable.
- Have diabetes. Beta blockers mask the warning signs of low blood sugar — the trembling and palpitations you would normally notice. This matters a great deal if you take insulin or a sulfonylurea.
- Have peripheral vascular disease or Raynaud’s — cold hands and feet are common.
- Have liver or kidney disease.
- Have depression.
- Are pregnant or breastfeeding.
- Take a calcium channel blocker such as verapamil or diltiazem, another heart rhythm medicine, or a diabetes medicine.
Follow the dispensing label. This page does not set doses, and the amount differs greatly between migraine prevention, tremor and heart conditions.
Possible cautions and when to ask a pharmacist or doctor
Do not stop suddenly — worth repeating, because people do it when side effects appear.
Masked hypoglycaemia in diabetes is the caution most likely to cause harm. If you take insulin or a sulfonylurea, you may lose the early warning symptoms of low blood sugar. Monitor more closely and know the symptoms that remain — sweating usually persists.
Cold hands and feet, fatigue and reduced exercise tolerance are common and dose-related.
Vivid dreams, nightmares and disturbed sleep occur because propranolol enters the brain. Report them; a beta blocker that crosses less may suit better.
Wheeze or breathlessness means stop and seek advice urgently.
Slow pulse or dizziness should be reported.
Depression and low mood are associated with beta blockers and worth mentioning.
Seek urgent medical attention for wheezing or difficulty breathing; a very slow pulse, fainting or marked dizziness; chest pain that is new or worse; swollen ankles with breathlessness; confusion; or symptoms of low blood sugar that are hard to recognise. If you have stopped the medicine suddenly and develop chest pain or palpitations, seek help immediately.
Related medicine guides
- Browse Heart, Blood Pressure & Circulation Medicines guides
- Read: Ciplavasc used for
- Read: Ridaq used for
Frequently asked questions
What is Indoblok 10 mg used for? High blood pressure, angina, irregular heart rhythms, migraine prevention, essential tremor, overactive thyroid symptoms, and the physical symptoms of anxiety. It contains propranolol.
Can I take it if I have asthma? Generally no. Propranolol can cause serious bronchospasm and is avoided in asthma. Tell your prescriber.
Does it treat anxiety? It blocks the physical symptoms — racing heart, trembling, sweating — but not the psychological experience. It is not a treatment for an anxiety disorder.
How does it prevent migraine? Taken daily, it reduces how often attacks occur. It takes several weeks to work and does not treat an attack in progress.
Can I stop taking it if I feel fine? No. Stopping abruptly causes a rebound surge in heart rate and blood pressure that can trigger angina or a heart attack. It must be tapered.
Why does it matter that I have diabetes? Beta blockers mask the early warning signs of low blood sugar, so you may not notice it coming. Monitor more closely.