Catapresan (Clonidine)
Centrally acting alpha-2 adrenergic agonist for hypertension and hypertensive crises
Quick Facts About Catapresan
Key Takeaways About Catapresan
- Never stop abruptly: Sudden discontinuation can cause dangerous rebound hypertension with rapid blood pressure elevation
- Injection form for emergencies: Catapresan injection is primarily used for hypertensive crises when oral therapy is not possible
- Causes significant sedation: Drowsiness and dry mouth are the most common side effects, affecting up to 40% of patients
- Multiple drug interactions: Beta-blockers, tricyclic antidepressants, and CNS depressants can interact dangerously with clonidine
- Monitor closely in elderly: Older adults are more susceptible to hypotension, sedation, and falls with clonidine use
What Is Catapresan and What Is It Used For?
Catapresan (clonidine hydrochloride) is a centrally acting alpha-2 adrenergic agonist available as a solution for injection (150 micrograms/mL). It is used primarily for hypertensive crises, severe hypertension requiring parenteral treatment, and as an adjunct in epidural analgesia for pain management.
Catapresan contains the active substance clonidine hydrochloride, which belongs to a group of medicines known as centrally acting antihypertensive agents. Unlike many other blood pressure medications that work directly on blood vessels or the heart, clonidine acts primarily in the brain. It stimulates alpha-2 adrenergic receptors in the brainstem, specifically in the nucleus tractus solitarius and the locus coeruleus, which reduces the sympathetic nervous system's "fight-or-flight" signals to the rest of the body.
This reduction in sympathetic outflow leads to several beneficial cardiovascular effects: decreased heart rate, reduced peripheral vascular resistance, lower cardiac output, and ultimately a decrease in blood pressure. The injectable form of Catapresan is particularly valuable in clinical settings where rapid blood pressure control is needed but oral medication cannot be used, such as in patients who are unable to swallow or who require immediate intervention for dangerously elevated blood pressure.
The injectable formulation is available as a 1 mL ampoule containing 150 micrograms of clonidine hydrochloride per millilitre. It can be administered intravenously (slowly, over 10-15 minutes), intramuscularly, or subcutaneously, depending on the clinical situation and the urgency of blood pressure reduction required.
Primary indications
The main clinical indications for Catapresan injection include:
- Hypertensive crises: Acute, severely elevated blood pressure (typically systolic above 180 mmHg and/or diastolic above 120 mmHg) requiring immediate pharmacological intervention to prevent organ damage
- Severe hypertension: When oral antihypertensive therapy is not feasible or has proven inadequate
- Perioperative blood pressure control: Management of acute hypertension during or after surgical procedures
- Epidural analgesia: As an adjunct to local anaesthetics or opioids for the management of severe cancer pain or postoperative pain (specific protocols apply)
Off-label uses
While the injectable form of clonidine is primarily indicated for hypertensive emergencies, oral formulations of clonidine have established off-label uses that are well-supported by clinical evidence. These include management of opioid withdrawal symptoms, attention deficit hyperactivity disorder (ADHD), menopausal flushing, Tourette syndrome, and migraine prophylaxis. Healthcare providers may occasionally use the injectable form in hospital settings for some of these purposes when oral administration is not possible.
Unlike ACE inhibitors, calcium channel blockers, or beta-blockers that act peripherally, clonidine works centrally in the brain to reduce sympathetic nervous system activity. This unique mechanism makes it particularly useful in certain clinical scenarios, but also means it has distinct side effects, primarily sedation and dry mouth, that are not typical of other antihypertensive drug classes.
What Should You Know Before Taking Catapresan?
Before receiving Catapresan, inform your healthcare provider about all medications you take, any history of depression, heart rhythm disorders, or kidney problems. Catapresan must never be stopped abruptly and requires special caution with beta-blockers, sedatives, and in elderly patients.
Catapresan injection is a potent medication with significant cardiovascular and neurological effects. Before it is administered, your healthcare team needs to have a complete picture of your medical history and current medications to ensure safe use. The following sections outline the most important safety considerations.
Contraindications
Catapresan injection should not be used in the following situations:
- Known hypersensitivity: Allergy to clonidine hydrochloride or any of the excipients in the formulation
- Severe bradyarrhythmias: Including sick sinus syndrome and second or third-degree atrioventricular (AV) block, unless a functioning pacemaker is in place
- Severe sinus node disease: Conditions where the heart's natural pacemaker is significantly compromised
Warnings and precautions
Special care and close monitoring are required in the following circumstances:
- Rebound hypertension: This is the most critical safety concern with clonidine therapy. Abrupt discontinuation can trigger a rapid and potentially dangerous rise in blood pressure, sometimes exceeding pre-treatment levels. This rebound phenomenon typically occurs 18-72 hours after the last dose and can manifest as headache, agitation, tremor, tachycardia, and in severe cases, hypertensive encephalopathy or stroke. Clonidine must always be tapered gradually over 2-4 days.
- Concurrent beta-blocker use: If a patient is taking both clonidine and a beta-blocker, the beta-blocker should be discontinued several days before clonidine tapering begins. This is because beta-blockers can exacerbate rebound hypertension by blocking the beta-adrenergic vasodilatory response while leaving alpha-adrenergic vasoconstriction unopposed.
- Cardiovascular disease: Patients with coronary artery disease, recent myocardial infarction, cerebrovascular disease, or chronic heart failure require particularly careful monitoring, as the haemodynamic changes induced by clonidine may be less well-tolerated in these populations.
- Renal impairment: Clonidine is partially excreted by the kidneys (approximately 40-60% as unchanged drug). Dose adjustments may be necessary in patients with significant renal impairment, and blood pressure response should be monitored more frequently.
- Depression: Clonidine has been associated with worsening of pre-existing depression. Patients with a history of depressive disorders should be monitored for changes in mood during treatment.
- Raynaud's disease or peripheral vascular disease: Clonidine can reduce peripheral blood flow and may worsen symptoms of these conditions.
- Pheochromocytoma: Clonidine is not effective as a sole antihypertensive agent in patients with pheochromocytoma, as the catecholamine excess overwhelms its central mechanism.
Pregnancy and breastfeeding
Clonidine crosses the placental barrier and has been detected in amniotic fluid. Animal reproductive studies have shown some evidence of foetal harm, although controlled human studies are limited. Catapresan should only be used during pregnancy when the potential benefits clearly outweigh the potential risks to the foetus. There have been reports of transient neonatal hypotension and bradycardia in infants born to mothers who received clonidine during pregnancy.
Clonidine is excreted in breast milk at concentrations approximately twice those found in maternal plasma. Given the potential for sedation and cardiovascular effects in nursing infants, breastfeeding is generally not recommended during clonidine therapy. If treatment is deemed essential, the infant should be closely monitored for signs of sedation, poor feeding, and cardiovascular effects.
Sudden discontinuation of clonidine can cause a potentially life-threatening rebound hypertensive crisis. Symptoms include severe headache, rapid heartbeat, tremor, agitation, and dangerous blood pressure elevation. If you miss doses or your treatment needs to be stopped, this must be done gradually over 2-4 days under medical supervision. If you are also taking a beta-blocker, it must be stopped first before tapering clonidine.
How Does Catapresan Interact with Other Drugs?
Catapresan has significant interactions with beta-blockers (risk of severe rebound hypertension), tricyclic antidepressants (reduced antihypertensive effect), CNS depressants (additive sedation), and other antihypertensives (enhanced blood pressure lowering). All concurrent medications should be reviewed by a healthcare provider.
Drug interactions with clonidine are clinically significant and can be potentially dangerous. The central mechanism of action of clonidine means it interacts with a wide range of medications that affect the cardiovascular and central nervous systems. Healthcare providers must carefully review all concurrent medications before administering Catapresan.
Major interactions
The following drug interactions are considered clinically significant and may require dose adjustments, alternative medications, or intensive monitoring:
| Drug/Class | Interaction Effect | Severity | Clinical Management |
|---|---|---|---|
| Beta-blockers (propranolol, metoprolol, atenolol) | Exacerbates rebound hypertension if clonidine stopped; may cause severe bradycardia | Major | Discontinue beta-blocker several days before tapering clonidine; monitor heart rate closely |
| Tricyclic antidepressants (amitriptyline, imipramine, nortriptyline) | Reduce or abolish antihypertensive effect of clonidine by blocking alpha-2 receptors | Major | Avoid combination; consider alternative antidepressant or antihypertensive |
| CNS depressants (benzodiazepines, opioids, barbiturates, alcohol) | Additive sedation, respiratory depression, and hypotension | Major | Reduce doses; monitor sedation level and respiratory function |
| Cardiac glycosides (digoxin) | Additive bradycardia and AV conduction delay | Major | Monitor heart rate and ECG; dose adjustments may be needed |
| Mirtazapine | May reduce antihypertensive effect (alpha-2 antagonist properties) | Moderate | Monitor blood pressure closely; consider alternative antidepressant |
Minor interactions
The following interactions are generally less severe but still warrant awareness and possible monitoring:
- Other antihypertensives (ACE inhibitors, ARBs, calcium channel blockers, diuretics): Additive blood pressure lowering effect. While these combinations can be therapeutically beneficial, dose titration should be careful to avoid excessive hypotension.
- Cyclosporine: Clonidine may increase plasma levels of cyclosporine, potentially enhancing its effects and toxicity. Monitoring of cyclosporine levels is recommended.
- Alpha-adrenergic blockers (prazosin, doxazosin): May partially antagonise the antihypertensive effect of clonidine while enhancing postural hypotension.
- Insulin and oral antidiabetic agents: Clonidine may mask the sympathetic symptoms of hypoglycaemia (tremor, tachycardia, sweating), making hypoglycaemia harder to detect in diabetic patients.
- Non-steroidal anti-inflammatory drugs (NSAIDs): May reduce the antihypertensive effect of clonidine through sodium and water retention.
- Methylphenidate: May decrease the effectiveness of clonidine, though this combination is sometimes used intentionally for ADHD management with oral clonidine.
What Is the Correct Dosage of Catapresan?
Catapresan injection dosage depends on the clinical situation and route of administration. For hypertensive crises in adults, the typical dose is 150-300 micrograms (1-2 ampoules) given by slow intravenous injection over 10-15 minutes. Doses must be individualised and administered under medical supervision with continuous blood pressure monitoring.
Catapresan injection is a hospital medication that should only be administered by trained healthcare professionals. The dosage must be carefully individualised based on the patient's blood pressure response, clinical condition, renal function, and concurrent medications. The following dosing guidelines represent standard recommendations, but actual doses may vary based on individual patient needs.
Adults
Hypertensive Crisis (Intravenous)
Dose: 150-300 micrograms (1-2 ampoules) diluted in 10 mL of sodium chloride 0.9%, administered by slow intravenous injection over 10-15 minutes.
Repeat: If necessary, a second dose may be given after 1-2 hours, depending on blood pressure response.
Maximum: Up to 750 micrograms in 24 hours, although most patients respond to lower doses.
Monitoring: Continuous blood pressure and heart rate monitoring during and for at least 30 minutes after administration.
Severe Hypertension (Intramuscular/Subcutaneous)
Dose: 150 micrograms (1 ampoule) administered intramuscularly or subcutaneously.
Repeat: May be repeated every 4-6 hours as needed, based on blood pressure response.
Note: Onset is slower via these routes (15-30 minutes) compared to IV administration (5-10 minutes).
Intravenous Infusion (Continuous)
Dose: 1.2-7.2 micrograms per kilogram of body weight per hour, titrated to blood pressure response.
Preparation: Dilute the required number of ampoules in sodium chloride 0.9% or glucose 5% to achieve the desired concentration.
Monitoring: Continuous haemodynamic monitoring in an intensive care setting.
| Patient Group | Route | Typical Dose | Special Considerations |
|---|---|---|---|
| Adults (hypertensive crisis) | IV slow injection | 150-300 mcg over 10-15 min | Continuous BP monitoring; max 750 mcg/24h |
| Adults (severe HTN) | IM or SC | 150 mcg every 4-6 hours | Slower onset; transition to oral when stable |
| Elderly patients | IV (preferred) | 75-150 mcg (start low) | Higher risk of hypotension, bradycardia, falls; titrate cautiously |
| Renal impairment | IV or IM | 75-150 mcg (reduced) | 40-60% renally excreted; extend dosing intervals |
Children
The use of Catapresan injection in children is limited and should only occur under specialist supervision. Paediatric dosing for parenteral clonidine is not well established, and off-label use in children is primarily based on clinical experience rather than large-scale clinical trials. When used, paediatric doses are calculated based on body weight, typically 1-5 micrograms per kilogram of body weight, administered slowly intravenously with careful haemodynamic monitoring.
In paediatric practice, oral clonidine is more commonly used than the injectable form, particularly for ADHD, Tourette syndrome, and sleep disturbances. Parents and caregivers should note that injectable clonidine is not interchangeable with oral formulations without careful dose recalculation by a physician.
Elderly
Elderly patients are particularly sensitive to the blood pressure-lowering and sedative effects of clonidine. Age-related reductions in renal function, changes in baroreceptor sensitivity, and increased risk of orthostatic hypotension all contribute to the need for lower initial doses and more gradual dose titration. Starting doses should generally be 50% of the usual adult dose, with careful upward titration based on blood pressure response and tolerability. Elderly patients should be closely monitored for signs of excessive sedation, confusion, and postural hypotension, particularly during the first 24-48 hours of treatment.
Missed dose
Since Catapresan injection is typically administered by healthcare professionals in a hospital setting, missed doses are managed by the clinical team. However, it is critically important to understand that if clonidine therapy is interrupted for any reason, rebound hypertension may occur. If a scheduled dose is missed, the healthcare team should assess the patient's blood pressure and administer the next dose as soon as clinically appropriate, without doubling the dose.
Overdose
Clonidine overdose can be serious and potentially life-threatening. Symptoms of overdose include profound hypotension, severe bradycardia, lethargy progressing to coma, hypothermia, respiratory depression, miosis (constricted pupils), and in children, intermittent episodes of hypertension may paradoxically occur. Treatment is primarily supportive and symptomatic:
- Atropine may be used for symptomatic bradycardia
- Intravenous fluids and vasopressors (e.g., norepinephrine) for severe hypotension
- Tolazoline (an alpha-adrenergic antagonist) has been used as a specific antidote, though its availability is limited
- Naloxone may partially reverse clonidine-induced CNS depression and hypotension
- Haemodialysis has limited effectiveness due to clonidine's high volume of distribution and protein binding
If a clonidine overdose is suspected, seek immediate medical attention. Clonidine overdose can cause dangerous drops in blood pressure and heart rate, severe sedation, and respiratory depression. In children, even small doses of clonidine can cause serious toxicity. Contact your local poison control centre or emergency services immediately.
What Are the Side Effects of Catapresan?
The most common side effects of Catapresan are dry mouth (up to 40%), drowsiness and sedation (up to 35%), dizziness, constipation, and headache. These are usually most pronounced at the start of treatment and tend to diminish over time. Serious but rare side effects include severe bradycardia, AV block, and rebound hypertension upon discontinuation.
Like all medicines, Catapresan can cause side effects, although not everybody gets them. The side effects of clonidine are largely predictable from its pharmacological mechanism of action: stimulation of alpha-2 receptors in the central nervous system leads to reduced sympathetic outflow, which causes effects on the cardiovascular system, the salivary glands, the gastrointestinal tract, and the central nervous system itself. Many side effects are dose-dependent and may diminish with continued use as the body adjusts to the medication.
The following frequency classification is used: very common (more than 1 in 10 patients), common (1 in 10 to 1 in 100), uncommon (1 in 100 to 1 in 1,000), and rare (less than 1 in 1,000).
Very Common (affects more than 1 in 10 patients)
- Dry mouth (xerostomia) – affects up to 40% of patients; may improve over time
- Drowsiness and sedation – affects up to 35%; particularly pronounced at treatment initiation
- Dizziness – especially when standing up (orthostatic)
- Headache – usually mild and transient
Common (affects 1 in 10 to 1 in 100 patients)
- Constipation – due to reduced gastrointestinal motility
- Nausea
- Orthostatic hypotension – drop in blood pressure when standing; risk of falls
- Fatigue and general malaise
- Erectile dysfunction – in male patients
- Sleep disturbances – vivid dreams or insomnia
- Bradycardia – slowed heart rate (usually mild)
- Pain at injection site – specific to parenteral administration
Uncommon (affects 1 in 100 to 1 in 1,000 patients)
- Depression or worsening of existing depression
- Parotid gland pain
- Raynaud's phenomenon – cold, pale fingers and toes
- Urinary retention
- Weight gain – due to fluid retention
- Gynaecomastia – breast tissue enlargement in males
- Decreased libido
Rare (affects less than 1 in 1,000 patients)
- Atrioventricular (AV) block – may require treatment discontinuation
- Hallucinations – primarily visual; more common in elderly patients
- Pseudo-obstruction of the colon (Ogilvie's syndrome)
- Alopecia – hair loss, usually reversible on discontinuation
- Skin rash or urticaria – allergic dermatitis
- Hepatitis – with elevated liver enzymes (very rare)
Most side effects of Catapresan are dose-related and improve with dose reduction or continued use. Dry mouth can be managed with sugar-free sweets, adequate fluid intake, or saliva substitutes. Constipation responds to dietary fibre, adequate fluids, and gentle laxatives if needed. Orthostatic hypotension can be minimised by advising patients to rise slowly from lying or sitting positions.
If you experience any severe or persistent side effects, or any symptoms not listed here, inform your healthcare provider immediately. In particular, seek urgent medical attention if you experience signs of severe bradycardia (extremely slow heartbeat, fainting), allergic reactions (swelling of face/tongue, difficulty breathing, severe rash), or symptoms suggesting rebound hypertension after dose reduction or discontinuation.
How Should You Store Catapresan?
Catapresan injection should be stored below 25°C, protected from light, and kept out of the reach of children. Do not use after the expiry date stated on the ampoule and carton. Once opened, the solution should be used immediately.
Proper storage of Catapresan injection is essential to maintain its efficacy and safety. As a hospital medication, storage is primarily the responsibility of pharmacy and nursing staff, but patients receiving home-based parenteral care should also be aware of these requirements.
- Temperature: Store below 25°C (77°F) at room temperature. Do not freeze.
- Light protection: Keep the ampoules in the original carton to protect from light. Clonidine solution may degrade with prolonged light exposure.
- Shelf life: Refer to the expiry date printed on the ampoule and outer carton. Do not use after this date.
- After opening: Catapresan ampoules are for single use only. Once opened, the solution should be used immediately and any remaining solution should be discarded.
- Visual inspection: Before use, visually inspect the solution for particulate matter and discolouration. The solution should be clear and colourless. Do not use if it appears cloudy or contains particles.
- Disposal: Do not dispose of unused medication via wastewater or household waste. Return any unused ampoules to the pharmacy for safe disposal.
What Does Catapresan Contain?
Each 1 mL ampoule of Catapresan contains 150 micrograms of clonidine hydrochloride as the active ingredient, along with sodium chloride, hydrochloric acid for pH adjustment, and water for injections as excipients.
Understanding the complete composition of Catapresan injection is important for identifying potential allergen concerns and ensuring compatibility with other intravenous solutions.
Active ingredient
Clonidine hydrochloride 150 micrograms per mL (equivalent to approximately 130 micrograms of clonidine base). Clonidine hydrochloride is an imidazoline derivative with the chemical name 2-(2,6-dichlorophenylamino)-2-imidazoline hydrochloride. It has a molecular weight of 266.56 g/mol and appears as a white, odourless, crystalline powder that is freely soluble in water.
Excipients (inactive ingredients)
- Sodium chloride: Added for isotonicity to ensure the solution is compatible with blood and tissue fluids
- Hydrochloric acid: Used for pH adjustment (the solution has a pH of approximately 4.0)
- Water for injections: High-purity water that serves as the vehicle for the active ingredient
The formulation is intentionally simple, containing no preservatives, which is why each ampoule is for single use only. The solution does not contain lactose, gluten, or common food allergens. Patients with known hypersensitivity to any of the listed excipients should inform their healthcare provider before receiving the injection.
Catapresan injection is compatible with sodium chloride 0.9% and glucose 5% solutions for dilution when preparing intravenous infusions. Compatibility with other IV solutions should be confirmed before mixing. Do not mix Catapresan with alkaline solutions, as the acidic pH of clonidine is important for its stability.
Frequently Asked Questions About Catapresan
Catapresan (clonidine) injection is primarily used for the treatment of hypertensive crises, which are dangerously high blood pressure episodes requiring immediate intervention. It is also used for severe hypertension when oral medication is not feasible, such as in patients who are unable to swallow or are in the intensive care unit. Additionally, clonidine is used as an adjunct in epidural analgesia for severe pain management. While the oral form of clonidine has broader off-label uses (including ADHD, opioid withdrawal, and menopausal flushing), the injectable form is primarily reserved for acute blood pressure emergencies.
Abruptly stopping Catapresan can cause rebound hypertension, which is a dangerous and rapid increase in blood pressure that may exceed pre-treatment levels. This typically occurs 18-72 hours after the last dose and can cause severe headache, agitation, tremor, rapid heartbeat, nausea, and in severe cases, hypertensive encephalopathy or stroke. For this reason, clonidine must always be tapered gradually over 2-4 days under medical supervision. If you are also taking a beta-blocker, this must be discontinued several days before the clonidine taper begins, as beta-blockers can worsen rebound hypertension.
Catapresan should only be used during pregnancy when the potential benefit clearly outweighs the risk to the foetus. Clonidine crosses the placenta and can cause transient neonatal hypotension and bradycardia. It is classified as FDA Pregnancy Category C, meaning animal studies have shown some adverse effects but there are no adequate controlled studies in pregnant women. Pregnant women requiring antihypertensive treatment should discuss alternative medications with their physician, such as methyldopa or labetalol, which have more established safety profiles in pregnancy.
The speed of onset depends on the route of administration. When given intravenously (slowly over 10-15 minutes), Catapresan begins to lower blood pressure within 5-10 minutes, with the peak effect typically occurring at 30-60 minutes. When administered intramuscularly or subcutaneously, the onset is slower at approximately 15-30 minutes, with peak blood pressure lowering at 1-2 hours. The duration of the blood pressure-lowering effect is approximately 6-8 hours per dose, regardless of the route of administration.
The most common side effects of Catapresan are dry mouth (affecting up to 40% of patients), drowsiness and sedation (up to 35%), dizziness (particularly when standing up), constipation, and headache. These effects are usually most prominent when treatment is first started and tend to diminish as the body adjusts. Orthostatic hypotension (a drop in blood pressure when standing) is also common, especially in elderly patients, and can increase the risk of falls. Most side effects are dose-dependent and may improve with dose reduction.
Catapresan can be used with beta-blockers, but this combination requires careful management, particularly when either drug needs to be discontinued. The main risk arises when clonidine is stopped: beta-blockers can dramatically worsen rebound hypertension by blocking the compensatory vasodilation that would normally limit the blood pressure rise. If both drugs need to be stopped, the beta-blocker should be discontinued several days before the clonidine taper begins. During concurrent use, patients should be monitored for excessive bradycardia and hypotension.
Catapresan is a brand name for the drug clonidine hydrochloride. The active ingredient is the same as in generic clonidine products. Catapresan is manufactured by Boehringer Ingelheim and is available in various formulations depending on the country, including tablets and injection solution. In many countries, generic clonidine tablets and other branded versions are also available. The injection form (150 micrograms/mL) is specifically marketed as Catapresan in many markets, though generic injectable clonidine is also available in some countries.
References
This article is based on peer-reviewed medical literature and international clinical guidelines. All medical claims are supported by evidence level 1A where available.
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Editorial Team
This article has been written and reviewed by the iMedic Medical Editorial Team, comprising licensed specialist physicians with expertise in clinical pharmacology, cardiology, and internal medicine. Our editorial process follows the GRADE evidence framework and adheres to international medical standards.
iMedic Medical Editorial Team – specialists in clinical pharmacology and cardiovascular medicine with documented academic and clinical experience.
iMedic Medical Review Board – independent panel of medical experts who verify all clinical content against current international guidelines (ESC/ESH, WHO, EMA, FDA, BNF).
Level 1A evidence – based on systematic reviews and meta-analyses of randomised controlled trials. All clinical claims are referenced to peer-reviewed sources.
No pharmaceutical company sponsorship or commercial funding. All content is editorially independent with no conflicts of interest.