Arkamin-H
Arkamin-H is Torrent’s fixed-dose clonidine 100 mcg + chlorthalidone 20 mg tablets — pairs central sympathetic suppression with long-acting thiazide-like natriuresis and vasodilation. Clinical role: resistant hypertension, intolerance to RAAS blockers, or patients already stable on the separate components. Not first-line. CRITICAL — never stop abruptly (clonidine rebound). Monitor potassium and sodium (chlorthalidone).
✓ Medically reviewed by Morgan Ellis — Pharmacy Researcher · 8 years experience · Last reviewed: May 2026
⚡ Quick Answer — What is Arkamin-H?
Arkamin-H is a fixed-dose tablet combining clonidine 100 mcg + 20 mg — a centrally-acting alpha-2 adrenergic agonist — with chlorthalidone, a long-acting thiazide-like diuretic, from Torrent Pharma. The combination pairs two complementary mechanisms for resistant or moderately-severe hypertension: clonidine reduces central sympathetic outflow (lowering BP and heart rate), while chlorthalidone produces sustained natriuresis and vasodilation. Typical dosing: one tablet once or twice daily. Never stop Arkamin-H abruptly — the clonidine component causes rebound hypertension with sympathetic surge within 18-36 hours. Taper over 2-4 weeks under medical supervision. Monitor electrolytes (chlorthalidone-driven hypokalaemia and hyponatraemia), BP, and heart rate on initiation and dose change. Not a first-line antihypertensive — reserve for resistant or clinic-specific indications after ACEi/ARB + CCB + thiazide + spironolactone have been tried or are contraindicated.
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What Is Arkamin-H?
Arkamin-H is an oral fixed-dose combination tablet supplying clonidine and chlorthalidone in a single pill (typical ratio 100 mcg clonidine + 20 mg chlorthalidone per tablet). Manufactured by Torrent Pharma and supplied in 30-180 tablets.
Clonidine was introduced by Boehringer Ingelheim in 1966 as Catapres — the first centrally-acting alpha-2 agonist. Chlorthalidone is a long-acting thiazide-like diuretic introduced by USV/Ciba in 1960, validated as first-line antihypertensive therapy in the ALLHAT trial (2002). The combination was developed to simplify resistant-hypertension regimens in the pre-ACEi era and remains a useful twin-mechanism option in modern resistant-HTN protocols.
Why Combine Clonidine with Chlorthalidone?
Resistant hypertension typically involves two physiological drivers: activated sympathetic tone and sodium retention. Addressing both simultaneously is more effective than either in isolation.
- Clonidine activates pre-synaptic alpha-2 receptors in the rostral ventrolateral medulla, suppressing descending sympathetic outflow. Peripheral noradrenaline falls 30-50%; heart rate drops 5-15 bpm; BP drops 10-30 mmHg.
- Chlorthalidone is a thiazide-like diuretic with a 40-60 hour duration, longer than hydrochlorothiazide. It reduces plasma volume over the first 1-2 weeks and contributes ongoing direct vasodilation via smooth-muscle potassium-channel effects.
- Complementary mechanisms — clonidine tends to cause salt and water retention over months (a well-known limitation of centrally-acting agents in monotherapy); chlorthalidone continuously offsets this.
The clinical role of Arkamin-H is narrower than in the 1970s — ACEi/ARB + CCB + thiazide + spironolactone combinations cover most modern hypertensive patients. Where it still fits: intolerance to RAAS blockers (cough, angioedema, hyperkalaemia), genuinely resistant HTN despite optimal first-line therapy, or patients already stable on individual clonidine + thiazide who benefit from single-tablet convenience.
Dosage & Titration
Standard dose: one 100 mcg + 20 mg tablet once or twice daily. Take at the same time(s) each day. Some patients are dosed twice daily to smooth the clonidine effect; others manage with once-daily dosing at bedtime.
Titration:
- BP not controlled on one tablet daily: increase to one tablet twice daily or add a complementary agent (ACEi, ARB, CCB) rather than increasing the clonidine component further.
- Sedation-limited: shift the larger dose to bedtime.
- Hypokalaemia on the chlorthalidone component: add or continue an ACEi/ARB (blunts thiazide-induced kalium loss) or add a low dose of a potassium-sparing agent.
Monitoring schedule:
- Baseline: BP (supine and standing), heart rate, urea, electrolytes (potassium, sodium), creatinine, eGFR, glucose, serum urate, ECG if clinically indicated.
- 1-2 weeks: repeat BP and U&E. Expect mild hypokalaemia and a small rise in serum urate.
- 4-6 weeks: BP target reassessment; full metabolic panel.
- Ongoing: annual U&E, urate, glucose, lipid panel. Never let supply lapse — rebound hypertension on missed doses.
- Stop and reassess on: potassium <3.0 or >5.5, sodium <130 with symptoms, severe sedation or depression, syncope, bradycardia <50 bpm or second/third-degree AV block, gout flare, persistent postural symptoms.
Side Effects
Common (>1%):
- Sedation, daytime drowsiness (clonidine effect)
- Dry mouth (clonidine effect — very common)
- Increased urination in the first 1-2 hours after dosing (chlorthalidone effect)
- Postural dizziness, orthostatic hypotension
- Hypokalaemia, mild hyponatraemia
- Hyperuricaemia and gout precipitation
- Modest worsening of glucose tolerance
- Constipation
- Erectile dysfunction, reduced libido
- Depression, mood change
- Peripheral oedema
Uncommon but clinically important:
- Rebound hypertensive crisis on abrupt discontinuation — stroke, MI, hypertensive encephalopathy reported
- Severe hyponatraemia — particularly in elderly women on low-salt diets
- Severe bradycardia, heart block (worsened by beta-blockers or digoxin)
- Stevens-Johnson syndrome — rare sulfonamide-class reaction to the chlorthalidone component
- Pancreatitis (rare thiazide class effect)
- Acute angle-closure glaucoma (rare sulfonamide-class reaction within hours to days of starting)
Contraindications
- Severe bradyarrhythmia, sick sinus syndrome, or second/third-degree AV block without pacemaker
- Severe renal impairment (eGFR <30) — chlorthalidone loses efficacy
- Anuria
- Sulfonamide hypersensitivity (chlorthalidone component)
- Known hypersensitivity to clonidine
- Severe depression (clonidine can deepen depressive symptoms)
- Baseline hypokalaemia (<3.0 mmol/L) or symptomatic hyponatraemia (<130 mmol/L)
- Hypercalcaemia
- Severe hepatic impairment (Child-Pugh C)
- Concurrent other central alpha-2 agonists (methyldopa, tizanidine, moxonidine)
Pregnancy: generally avoided as first-choice. In pregnancy HTN, prefer methyldopa, labetalol, or nifedipine — all three have larger safety databases. Thiazides in pregnancy can cause neonatal jaundice and thrombocytopenia; clonidine crosses the placenta but is not clearly teratogenic. Use only for compelling indications under specialist supervision.
Breastfeeding: both components enter breast milk. Monitor infant for sedation, bradycardia, poor feeding; consider alternative regimens where possible.
Drug Interactions
- Beta-blockers — CRITICAL. Co-therapy worsens clonidine-withdrawal rebound and increases bradycardia risk. If discontinuing both, stop the beta-blocker several days before tapering clonidine.
- Lithium — CRITICAL. Chlorthalidone reduces lithium clearance; combination can precipitate lithium toxicity. Monitor levels weekly for the first month if unavoidable; reduce lithium dose by 25-50%.
- Tricyclic antidepressants — partially antagonise clonidine’s antihypertensive effect and add orthostatic hypotension.
- Other central alpha-2 agonists (methyldopa, tizanidine, moxonidine) — additive sedation and hypotension; do not combine.
- NSAIDs — reduce diuretic and antihypertensive effect; substantially raise AKI risk when combined with ACEi/ARB.
- Digoxin — hypokalaemia potentiates digoxin toxicity; additive bradycardia. Monitor levels.
- Oral corticosteroids, amphotericin B, laxatives — additive hypokalaemia.
- CNS depressants (opioids, benzodiazepines, alcohol, gabapentinoids) — additive sedation.
- Cholestyramine / colestipol — reduce chlorthalidone absorption. Separate doses by 4 hours.
- Oral antidiabetic drugs, insulin — thiazides worsen glucose tolerance; may require dose adjustment.
- Alcohol — additive orthostatic hypotension and sedation.
Storage
Store Arkamin-H below 25°C in the original blister pack. Keep out of reach of children.
Frequently Asked Questions
Why would my doctor choose Arkamin-H over separate clonidine and chlorthalidone tablets?
Single-tablet fixed-dose combinations improve adherence substantially — patients forget one pill less often than two, and reducing pill burden is one of the strongest predictors of BP control. The 100 mcg + 20 mg ratio in Arkamin-H matches the proportions typically used in clinical practice; patients stable on the components separately can be switched to the combination tablet one-for-one.
Is Arkamin-H a first-line blood-pressure drug?
No — modern guidelines start with ACE inhibitors, ARBs, calcium-channel blockers, or thiazide/thiazide-like diuretics as first-line monotherapy or in pairs, then add spironolactone as the preferred fourth agent (PATHWAY-2 evidence). Clonidine-based combinations are typically reserved for resistant hypertension, intolerance to RAAS blockers, or patients already stable on clonidine.
What happens if I forget a dose of Arkamin-H?
Take the missed dose as soon as you remember, even if it is close to the next scheduled time — clonidine has a rebound-hypertension risk on missed doses that other antihypertensives do not share. If you realise within a few hours, take the dose; if the next dose is due within 2-3 hours, take the next dose at the normal time but do not double up. If you have missed an entire day and feel headache, palpitations, or sweating, take the dose and seek urgent medical review. Never let your supply run out.
Will Arkamin-H affect my potassium?
Yes — the chlorthalidone component lowers potassium (and sodium). Check potassium at baseline, at 1-2 weeks, and periodically thereafter. Risk is minimised by combining with an ACE inhibitor or ARB (which blunt thiazide-induced kalium loss). Clonidine itself is potassium-neutral.
Will I be drowsy?
Yes, especially in the first 2-4 weeks — the clonidine component causes sedation in most patients. It usually improves substantially by week 4-6. Shift the larger dose to bedtime to move sedation into sleep; avoid alcohol and other sedating drugs; do not drive until you know how Arkamin-H affects you.
Can I take ibuprofen with Arkamin-H?
Occasional short-term use is usually fine. Chronic daily NSAIDs reduce the antihypertensive effect of Arkamin-H and substantially raise AKI risk when combined with an ACE inhibitor or ARB (the “triple whammy”). Use paracetamol preferentially for chronic pain.
Can I take Arkamin-H in pregnancy?
Generally no. Pregnancy antihypertensives of choice are methyldopa, labetalol, and nifedipine. Thiazides in pregnancy can cause neonatal jaundice and thrombocytopenia, and clonidine has a smaller safety database than the preferred agents. Switch pre-conception or as soon as pregnancy is confirmed, under specialist supervision.
Where can I buy Arkamin-H online?
You can buy Arkamin-H (100 mcg + 20 mg clonidine + chlorthalidone, 30-180 tablets) from MedsBase with discreet packaging and worldwide shipping.
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| Strength | 100 mcg + 20 mg |
|---|---|
| Quantity | 30 Tablet/s, 60 Tablet/s, 90 Tablet/s, 180 Tablet/s |
Arkamin-H
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