Aximin 550 mg Tab

Aximin 550 mg Tablet (Rifaximin) — Clinical Overview

What is Aximin 550 mg?

Aximin 550 mg Tab is a high-dose formulation of rifaximin, manufactured by ACI Limited, Bangladesh. It is a non-systemic, gut-selective antibiotic of the rifamycin class — meaning it acts exclusively within the gastrointestinal tract without significant absorption into the bloodstream (<0.4% systemic bioavailability). At the 550 mg dose, rifaximin is clinically validated for two major indications: hepatic encephalopathy (HE) prevention in cirrhotic patients and irritable bowel syndrome with diarrhoea (IBS-D).

Aximin 550 mg is a distinct, higher-dose product from Aximin 200 mg (used for traveller's diarrhoea and SIBO). The two products should not be interchanged — dosing and indications differ significantly.

Mechanism of Action

Rifaximin inhibits bacterial RNA polymerase by binding irreversibly to its beta-subunit, halting mRNA synthesis and killing susceptible gut bacteria. At 550 mg, the same mechanism operates but achieves higher intraluminal concentrations, providing:

• Effective suppression of ammonia-producing colonic bacteria (e.g., urease-producing E. coli and Proteus) that drive hepatic encephalopathy
• Modulation of the gut microbiome in IBS-D — reducing bloating, abdominal pain, and loose stools by altering bacterial composition without eliminating it
• Essentially zero systemic exposure — avoiding hepatic, renal, and immune system effects

Clinical Indications

• Hepatic encephalopathy (HE) — prevention of recurrence: In patients with liver cirrhosis who have experienced ≥2 overt HE episodes, rifaximin 550 mg twice daily reduces the risk of HE recurrence and HE-related hospitalisations. Used alongside lactulose in most protocols.
• Overt HE episodes: 550 mg three times daily × 5–14 days to treat an acute episode
• IBS with diarrhoea (IBS-D): 550 mg three times daily × 14 days — reduces bloating, abdominal pain, and loose stool frequency. Approximately 40% of patients achieve symptom relief; treatment can be repeated.

Hepatic Encephalopathy and Rifaximin 550 mg

Hepatic encephalopathy (HE) is a serious neuropsychiatric complication of liver cirrhosis caused by accumulation of gut-derived toxins (principally ammonia) in the blood when the liver cannot adequately detoxify the portal circulation. Gut bacteria produce ammonia from dietary protein via urease enzymes — and rifaximin 550 mg suppresses these bacteria, reducing ammonia production at source:

• Landmark RFHE3001 trial: Rifaximin 550 mg BID reduced HE breakthrough episodes by 58% and hospitalisation by 50% compared to placebo over 6 months
• Benefits maintained in patients with Model for End-Stage Liver Disease (MELD) scores up to 25
• Particularly useful when lactulose alone is insufficient or poorly tolerated
• Long-term use (≥12 months) is well-tolerated with no emergence of clinically significant resistance

Diabetes and Hepatic/GI Conditions — Special Relevance

Diabetic patients face elevated risk of conditions that rifaximin 550 mg addresses:

• Non-alcoholic steatohepatitis (NASH) and cirrhosis: Type 2 diabetes is a major risk factor for NASH — the leading cause of cirrhosis in non-alcoholic patients. Diabetic patients with established cirrhosis are at high risk of HE. Rifaximin 550 mg is indicated for HE prevention in this group.
• IBS-D in diabetics: Diabetic autonomic neuropathy affects the entire GI tract. Many diabetics experience functional bowel symptoms indistinguishable from IBS-D. A 14-day rifaximin course may provide meaningful symptom relief.
• Glucose management in cirrhosis: Cirrhotic patients commonly develop hepatogenous diabetes (from impaired hepatic glucose regulation). Rifaximin's lack of systemic absorption means no pharmacokinetic interactions with insulin, metformin, or oral antidiabetics.
• Nutritional considerations: HE management requires careful protein restriction and timing. Coordinate rifaximin therapy with dietitian review in diabetic-cirrhotic patients who need both glucose and protein management.

Dosage and Administration

• HE prevention (maintenance): 550 mg twice daily (every 12 hours) — long-term, ongoing
• Overt HE episodes: 550 mg three times daily × 5–14 days
• IBS-D: 550 mg three times daily × 14 days (can be repeated for recurrent episodes)

May be taken with or without food. Swallow tablets whole. Do not crush or chew.

Drug Interactions

• Warfarin: Modest increase in INR reported — monitor closely
• Ciclosporin: Elevates rifaximin plasma levels via P-gp inhibition — avoid if possible
• Antidiabetics (metformin, insulin, DPP-4 inhibitors, SGLT-2 inhibitors): No clinically significant pharmacokinetic interactions due to negligible systemic absorption

Side Effects

• Common: Peripheral oedema, nausea, dizziness, fatigue, ascites (in cirrhotic patients)
• Uncommon: Headache, abdominal pain, constipation
• Rare: Hypersensitivity reactions; C. difficile infection (rare)

Contraindications

• Known hypersensitivity to rifaximin, rifamycins, or any excipient
• Intestinal obstruction
• Severely decompensated cirrhosis with MELD >25 (limited data — use with specialist guidance only)

Frequently Asked Questions (FAQ)