Nitroglycerin Extended-Release Capsules (2.5 mg & 6.5 mg)

Nitroglycerin extended-release capsules deliver glyceryl trinitrate, a nitrate vasodilator, in a slow-release oral form designed to prevent angina attacks rather than treat one already under way. We supply this capsule in 2.5 mg and 6.5 mg strengths, and understanding how the medicine works, how it is generally used, and how it differs from other nitrate products can help you decide whether it fits your needs and what to discuss with your prescriber.

What this medicine is

The active ingredient is glyceryl trinitrate, known in many countries as nitroglycerin. It belongs to the organic nitrate class of anti-anginal medicines, and in this listing it is supplied as an extended-release capsule taken by mouth, distinct from sublingual tablets, sprays, patches, or ointment forms of the same ingredient. The capsule releases glyceryl trinitrate gradually, giving a longer effect than a fast-acting nitrate and making it suited to routine prevention rather than rapid relief of an acute attack.

Angina and why nitrates matter

Angina pectoris develops when the heart muscle does not receive enough oxygen-rich blood for its current workload, usually because coronary artery disease restricts blood flow. Symptoms may be triggered by exertion, cold weather, a large meal, or emotional stress and can include pressure, tightness, heaviness, or pain in the chest, sometimes spreading to an arm, shoulder, jaw, neck, back, or upper abdomen. Breathlessness, nausea, or unusual fatigue can also occur.

Long-term prevention may combine lifestyle measures, management of cardiovascular risk factors, and medicines such as beta-blockers, calcium channel blockers, antiplatelet treatment, lipid-lowering therapy, or a nitrate. A new, severe, persistent, or changing pattern of chest pain needs urgent assessment because it may represent unstable angina or a heart attack rather than the person's usual stable symptoms.

How glyceryl trinitrate works

After absorption, glyceryl trinitrate is bioactivated to nitric oxide and related signalling species. These increase cyclic guanosine monophosphate in vascular smooth muscle, causing the muscle to relax. Veins generally dilate more than arteries, reducing the volume of blood returning to the heart and lowering the pressure the heart must work against. Nitrates can also dilate coronary vessels and relieve coronary spasm. The overall result is a reduction in myocardial wall stress and oxygen demand, helping to prevent the supply-and-demand mismatch that produces angina.

The extended-release design matters here: instead of producing the rapid peak associated with a sublingual product, the capsule releases the medicine more gradually. This supports its preventive role, but sustained nitrate exposure can lead to tolerance. A planned period without nitrate exposure is therefore normally incorporated into the daily regimen.

Evidence behind nitrate therapy

Organic nitrates have been used in cardiovascular medicine for well over a century, and their ability to relieve and help prevent angina symptoms is well established. Studies and extensive clinical experience show that appropriately scheduled long-acting nitrates can reduce angina frequency and improve exercise tolerance in some patients. The response varies, however, and benefit may diminish when nitrate concentrations are maintained continuously.

Extended-release oral preparations are intended to provide preventive activity for part of the day rather than uninterrupted round-the-clock exposure. Evidence on nitrate tolerance supports including a daily nitrate-free interval, commonly around 10 to 12 hours, although the exact schedule must be selected by the prescriber for the individual product and patient. Nitrates control symptoms; they have not been shown to reverse coronary artery disease or independently improve survival, so they do not replace wider cardiovascular risk management.

Formulation details

Each capsule contains glyceryl trinitrate in a modified-release formulation. The precise release technology and inactive ingredients can vary by manufacturer, so people with allergies or dietary restrictions should check the supplied patient information leaflet and packaging. Extended-release capsules should normally be swallowed whole with water and must not be chewed or crushed, as damaging the formulation may alter release of the dose. Do not open a capsule unless the directions for the specific supplied product expressly permit it. Follow its instructions about meals and take each dose in a consistent way.

Established uses

The recognised use for this extended-release capsule is the prevention of angina pectoris associated with coronary artery disease in adults. It is not intended to stop an angina attack that has already started, a role for which a fast-acting sublingual glyceryl trinitrate tablet or spray may be prescribed. Nitrates in other formulations are used in additional cardiovascular settings, including selected cases of acute or chronic heart failure, but that does not make every nitrate formulation interchangeable. The extended-release oral capsule is specifically a maintenance treatment for reducing angina symptoms.

Strengths, pack options and general dosing principles

We offer this capsule in 2.5 mg and 6.5 mg strengths. Each strength is available in packs of 30, 60, 90, 120, 180, 270, or 360 capsules, allowing customers to match the quantity to their planned supply.

Extended-release glyceryl trinitrate is generally started at a low dose, with the strength, timing, and number of daily doses adjusted according to symptom control, blood pressure, adverse effects, and the directions for the specific preparation. Because sustained nitrate exposure can blunt the response, the schedule should provide a daily nitrate-free interval rather than evenly spaced coverage throughout all 24 hours. Patients should not create this interval, alter their dose, or stop treatment abruptly without advice from their prescriber, as poorly timed changes may allow angina to worsen.

Swallow each dose as directed and try to take it at the same times each day. If a dose is missed, follow the product leaflet or ask a pharmacist; do not take two doses together to compensate. This is general information rather than a personal regimen, and the instructions supplied by the prescriber and with the exact product take priority.

Onset, duration and elimination

Glyceryl trinitrate itself is metabolised rapidly, with a plasma half-life measured in minutes. The extended-release capsule prolongs delivery of the active ingredient, so its preventive effect develops more gradually and lasts for several hours rather than producing the near-immediate but short-lived action expected from a sublingual tablet or spray.

Glyceryl trinitrate undergoes extensive first-pass metabolism, principally to dinitrate and mononitrate metabolites. Some metabolites retain vasodilator activity and have longer half-lives than the parent compound before further metabolism and elimination, including renal excretion of metabolites. Nitrate tolerance is associated with sustained exposure and adaptive vascular and biochemical responses, not simply with the parent medicine's short plasma half-life.

Safety essentials

The most important safety principle with any nitrate is that it must not be combined with phosphodiesterase type 5 inhibitors such as sildenafil, tadalafil, or vardenafil, or with the pulmonary hypertension medicine riociguat. The combined vasodilating effect can cause a severe and potentially life-threatening fall in blood pressure. The period for which a phosphodiesterase type 5 inhibitor remains relevant differs between medicines, so patients should tell the prescriber or emergency team exactly which product they used and when.

Alcohol and other blood-pressure-lowering medicines can add to dizziness, light-headedness, or fainting. Rise slowly from sitting or lying down, particularly when treatment is started or the dose changes, and avoid driving, cycling, or operating machinery until you know how the medicine affects you. Anyone who is pregnant should discuss treatment with a clinician because adequate controlled human data are lacking. Caution is also advised during breastfeeding because it is not established whether glyceryl trinitrate passes into human milk. Safety and effectiveness have not been established in children.

Monitoring and practical use

Before treatment, a clinician should review blood pressure, the pattern of chest symptoms, other cardiovascular conditions, and all prescription medicines, over-the-counter products, and recreational drugs. During treatment, useful measures of response include the frequency and severity of angina, use of fast-acting rescue medicine, exercise tolerance, blood pressure, headaches, dizziness, and any episodes of fainting. Increasing attacks, reduced exercise capacity, or a growing need for rescue medicine warrants medical review rather than an unsupervised increase in the capsule dose.

Extended-release capsules should not be relied upon during an acute attack. If a rapid-relief glyceryl trinitrate product has been prescribed, keep it accessible and follow the individual angina action plan. Stop exertion and seek emergency help by calling 999 if pain is severe, feels different from usual, occurs at rest, or does not settle as instructed after use of the prescribed rapid-relief treatment. Do not delay emergency assessment by taking extra extended-release capsules.

Glyceryl trinitrate reduces symptoms but does not remove the need to address smoking, blood pressure, cholesterol, diabetes, physical activity, diet, or other cardiovascular risk factors. These should be reviewed with the appropriate healthcare professional as part of the broader coronary artery disease treatment plan.

Prescription status and how to order with us

Glyceryl trinitrate capsules are classified as prescription-only medicines in the United Kingdom, which describes their legal status in the UK market. Separately, our checkout does not require you to upload or submit a prescription before we accept your order. The medicine's UK classification and our product-specific ordering policy are distinct points.

Because this nitrate has important contraindications and interaction risks, appropriate medical guidance should be in place before treatment is started or continued. Our pharmacist team is available by email, online chat, or phone, 24/7, if you have questions before or after ordering. A current UK marketing authorisation for this exact glyceryl trinitrate capsule product in the listed strengths has not been confirmed against the MHRA medicines registers; customers for whom this distinction matters can check the applicable register entry or ask our team. Suspected adverse effects can be reported through the MHRA Yellow Card Scheme.

Who should avoid this medicine

Do not use this medicine if you have had a hypersensitivity reaction to glyceryl trinitrate, another organic nitrate, or an ingredient in the capsule. Concomitant use with a phosphodiesterase type 5 inhibitor or riociguat is contraindicated because of the risk of profound hypotension.

Glyceryl trinitrate may also be unsuitable, or require specialist assessment, in people with severe hypotension, marked hypovolaemia, severe anaemia, acute circulatory failure, raised intracranial pressure, or a condition that depends on maintaining adequate cardiac filling pressure. Examples include right ventricular infarction, cardiac tamponade, constrictive pericarditis, hypertrophic obstructive cardiomyopathy, and severe aortic or mitral stenosis. These conditions should not be treated as interchangeable, and the individual haemodynamic risk must be assessed by a clinician. An unspecified allergy history alone is not a nitrate contraindication; the concern is a known reaction to an organic nitrate or a capsule ingredient.

Interactions to be aware of

• Phosphodiesterase type 5 inhibitors such as sildenafil, tadalafil, and vardenafil, and riociguat: combined use can cause severe, dangerous hypotension and must be avoided.
• Other blood-pressure-lowering medicines, including beta-blockers, calcium channel blockers, ACE inhibitors, angiotensin receptor blockers, diuretics, and alpha-blockers: additive effects may increase dizziness or fainting and can require clinical monitoring.
• Alcohol: may intensify flushing, dizziness, and low blood pressure.
• Other nitrates and vasodilators: duplicate nitrate exposure can increase adverse effects and promote tolerance unless the combination is specifically managed by a prescriber.
• Medicines that can contribute to methaemoglobinaemia: concurrent exposure may increase the risk of this rare complication and should be reviewed by a clinician or pharmacist.

Always provide an up-to-date list of medicines and supplements when glyceryl trinitrate is prescribed. Interaction screening is particularly important before treatment for erectile dysfunction or pulmonary hypertension is started.

Possible side effects and when to act

Headache is the most frequently reported effect, particularly when treatment begins or the dose increases. It can be pronounced but often becomes less troublesome as the body adjusts. Flushing, dizziness, light-headedness, weakness, nausea, and a faster heartbeat can also occur. Headache may indicate that the medicine is exerting a vascular effect, but persistent or severe symptoms still deserve advice; patients should not alter the nitrate schedule or take a headache medicine without checking that it is suitable for them.

Seek prompt medical advice for fainting, severe or persistent dizziness, a marked fall in blood pressure, worsening angina, or an unusually slow or rapid heartbeat. Rarely, excessive nitrate exposure can cause methaemoglobinaemia, reducing the blood's ability to carry oxygen. Possible signs include blue or grey discolouration of the lips, skin, or nail beds, shortness of breath, unusual tiredness, confusion, or a rapid heartbeat. Severe symptoms, collapse, or chest pain that does not settle require emergency care through 999 or A&E.

Overdose and toxicity

Taking substantially more than directed can cause pronounced hypotension, severe throbbing headache, flushing, sweating, nausea, vomiting, visual disturbance, confusion, and a rapid pulse that may later slow. High exposure can cause methaemoglobinaemia with cyanosis and breathing difficulty; severe poisoning may lead to collapse, seizures, coma, or cardiovascular compromise.

A suspected overdose is a medical emergency. Call 999 for severe symptoms or follow urgent advice from NHS 111 when appropriate, and keep the packaging available so healthcare professionals can identify the product and strength. Do not induce vomiting or try to manage the overdose by giving additional medicines. Hospital treatment is supportive and may include positioning, intravenous fluids, cardiovascular monitoring, and specific treatment for confirmed clinically significant methaemoglobinaemia.

Storage

Store these capsules at 20°C to 25°C in a tightly closed container, protected from light and moisture. Keep them out of the sight and reach of children, and do not use them after the stated expiry date. Avoid transferring capsules to an unsuitable container that does not protect them adequately. A pharmacist can advise how to dispose of expired or unwanted capsules; they should not be put into household wastewater.

Benefits and trade-offs of this form

An extended-release oral capsule provides planned maintenance exposure without the skin irritation, adhesion problems, and application-site rotation associated with a transdermal patch. It may suit someone who prefers an oral preventive medicine and can follow a deliberately uneven schedule that includes a nitrate-free interval.

The trade-off is that the capsule acts too slowly to replace a sublingual tablet or spray during an angina attack. Unlike a rapid-relief product used when symptoms occur or shortly before a predictable trigger, this capsule is taken as scheduled maintenance treatment. The nitrate-free interval also means that uninterrupted protection is not the objective, so the timing should reflect when symptoms are most likely while minimising tolerance. Headache and blood-pressure effects can limit the usable dose, and individual response can vary.

Nitroglycerin capsules and related anti-anginal options

Nitroglycerin may be sold generically or under different brand names in various markets. Products with the same active ingredient are not automatically interchangeable unless the strength, dosage form, and modified-release characteristics are equivalent. A pharmacist or prescriber should confirm suitability before a patient changes between extended-release preparations.

Other glyceryl trinitrate products include sublingual tablets, translingual sprays, transdermal patches, and topical preparations. Sublingual tablets and sprays provide rapid, short-lived action for an acute attack or a predictable trigger. Patches deliver medicine through the skin for preventive use but must also be scheduled to limit tolerance. Topical preparations have their own dosing and application requirements. These forms should not be substituted dose for dose.

Isosorbide dinitrate and isosorbide mononitrate use the same nitric-oxide pathway but differ in bioavailability, onset, duration, metabolism, and usual schedules. Non-nitrate anti-anginal medicines include beta-blockers such as metoprolol, calcium channel blockers, and other options chosen according to heart rate, blood pressure, ventricular function, associated conditions, and treatment response. They may be used instead of or alongside a long-acting nitrate, but they are not direct equivalents. Discussing these distinctions with a prescriber helps ensure that the selected form, strength, regimen, and pack size fit the overall treatment plan.