Is modafinil safe? Your heart, blood pressure and long-term use

Is modafinil safe? For adults with narcolepsy who are checked and monitored by a prescriber, UK regulators judge that its benefits outweigh its risks. But modafinil can raise your heart rate and blood pressure and, less often, cause an irregular heartbeat. That is why you need an ECG before you start and regular blood pressure and heart rate checks while you take it.

This guide explains how modafinil can affect your heart and blood pressure, who should not take it, and which checks UK guidance asks for. It also covers what is known, and not known, about long-term use. For an overview of the medicine, read our complete guide to modafinil.

Is modafinil safe? What UK regulators decided

In 2010 the European Medicines Agency reviewed every use of modafinil. Its referral review noted a link between modafinil and heart and blood vessel problems, such as high blood pressure and an irregular heartbeat. It also noted psychiatric side effects.

The review concluded that the benefits outweigh the risks only in narcolepsy. The MHRA Drug Safety Update on the narcolepsy restriction confirmed that modafinil is no longer licensed in the UK for shift-work sleep disorder or obstructive sleep apnoea.

So “safe” here has a specific meaning. It means acceptable for adults with narcolepsy, when a prescriber has checked that it suits them and keeps reviewing them. It does not mean risk-free, and it does not cover other uses.

How modafinil can affect your heart and blood pressure

The UK Summary of Product Characteristics (SmPC) for modafinil lists these heart and circulation side effects. They come from clinical trials involving 1,561 patients.

Side effect	How often (SmPC)
Fast heartbeat (tachycardia), palpitations	Common (between 1 in 10 and 1 in 100 people)
Chest pain	Common
Widening of blood vessels (vasodilatation)	Common
High blood pressure or low blood pressure	Uncommon (between 1 in 100 and 1 in 1,000 people)
Irregular heartbeat (arrhythmia), extra beats (extrasystoles), slow heartbeat (bradycardia)	Uncommon
Abnormal heart trace (ECG)	Uncommon

The patient information leaflet puts this in plain words. Common effects include being aware of your heartbeat, which may be faster than normal, and chest pain. Uncommon effects include changes in blood pressure and an irregular or unusually slow heartbeat.

The NHS narcolepsy treatment page gives the same message. It says modafinil has been linked to irregular heartbeats and increases in blood pressure, so you will need regular monitoring.

Our modafinil side effects guide covers the other effects, such as headache, anxiety and skin reactions.

Who should not take modafinil

The SmPC says you must not take modafinil if you have:

• uncontrolled moderate to severe high blood pressure (hypertension)
• a heart rhythm problem (cardiac arrhythmia)
• an allergy to modafinil or any of the other ingredients

It is also not recommended if you have had left ventricular hypertrophy (thickening of the heart’s main pumping chamber) or cor pulmonale (strain on the right side of the heart from lung disease). The same applies if you have mitral valve prolapse and had mitral valve prolapse syndrome with a stimulant medicine in the past. The SmPC says this syndrome can show as chest pain, an irregular heartbeat or changes on an ECG.

The leaflet asks you to tell your doctor before you start if you have any heart problems or high blood pressure. Your doctor will then check these regularly.

Heart checks before and during treatment

Before you start: an ECG

The SmPC recommends an ECG (a recording of your heart’s electrical activity) for everyone before modafinil is started. If the ECG shows anything abnormal, you should see a specialist and have that treated before modafinil is considered. The MHRA gave the same advice to doctors.

While you take it: blood pressure and heart rate

The MHRA says blood pressure and heart rate should be monitored regularly. Your prescriber will decide how often. Keep these appointments even if you feel well.

The NHS high blood pressure guide explains why. High blood pressure does not usually cause any symptoms, so a check is the only way to know. Many pharmacies and GP surgeries can check your blood pressure.

If you check at home, the NHS says a reading of 135/85 or higher counts as high. A reading of 140/90 or higher counts as high when a healthcare professional takes it. Share your home readings with your prescriber.

If problems appear

The SmPC says modafinil should be stopped in anyone who develops an irregular heartbeat or moderate to severe high blood pressure. It should not be restarted until the problem has been properly assessed and treated. This is a decision for your prescriber, so contact them promptly rather than changing your dose yourself.

What the blood pressure research shows

There is not much published research that measures modafinil’s effect on blood pressure in detail. One small trial, published in Clinical Pharmacology & Therapeutics in 1999, compared modafinil with a dummy tablet (placebo) over two days.

It involved 26 men with mild to moderate obstructive sleep apnoea. At rest, the difference in the main blood pressure measure was small and not statistically significant. During exercise and a mental stress test, though, systolic blood pressure was up to about 6 mmHg higher with modafinil.

The study had clear limits. It was short, small, only included men and did not include people with high blood pressure. Its authors said longer studies including people with high blood pressure were needed. This is one reason UK guidance relies on checking each person, rather than assuming the effect will be small.

Modafinil long-term use: what we know

Many people with narcolepsy take modafinil for years. The UK product information is open about the gaps in the evidence:

• Long-term benefit: the SmPC says long-term efficacy beyond 9 weeks has not been evaluated. Your prescriber should review regularly whether it is still helping you.
• Heart and blood pressure: the need for regular checks applies for as long as you take it. The EMA asked the makers for further studies on heart and skin safety.
• Dependence: the SmPC says some studies showed a potential for dependence, and the possibility with long-term use cannot be entirely excluded.
• Sleepiness: your wakefulness may not return to fully normal levels, so talk to your doctor about whether it is safe for you to drive.
• Sleep: because modafinil promotes wakefulness, look out for trouble sleeping and mention it at your review.

The usual starting dose in adults is 200 mg a day, and people over 65 usually start on 100 mg a day, according to the SmPC. Always take it exactly as your prescriber tells you.

Heart medicines and modafinil

Tell your prescriber and pharmacist about every medicine you take. The SmPC mentions a few that matter for people with heart conditions:

• Propranolol (a beta-blocker): modafinil may slow how fast your body clears it, so the dose may need to be lowered.
• Warfarin (a blood thinner): modafinil may slow how fast your body clears warfarin, so your clotting (prothrombin time) should be checked regularly in the first 2 months.
• Ciclosporin: one patient’s ciclosporin level fell by half while taking modafinil.

Modafinil can also make hormonal contraception less effective. Our guide to modafinil, pregnancy and contraception explains which methods still work.

Caffeine can add to a fast heartbeat and palpitations. Our guide to modafinil, alcohol, caffeine and other interactions covers this and other medicines in more detail.

Is modafinil safe if it was not prescribed for you?

Some people take modafinil to try to stay alert or focus for work or study. It is not licensed for this in the UK, and nobody checks their heart before or during use. A letter in The Pharmaceutical Journal warned that claims about it being a safe “smart drug” rest on small studies, many using single doses.

Our guides to modafinil and UK law and how to check a UK online pharmacy explain more.

This article is for information only and does not replace advice from your doctor or pharmacist. Read our medical disclaimer.