Avlotrin 160 mg Tablet

Product Overview

What Is Avlotrin DS (Co-trimoxazole)?

Avlotrin DS is a double-strength fixed-dose combination antibiotic manufactured by ACI Limited, Bangladesh, containing Trimethoprim 160 mg and Sulfamethoxazole 800 mg per tablet. Co-trimoxazole exploits the synergy of two agents that each block a distinct step in the bacterial folate synthesis pathway, achieving bactericidal activity at concentrations where either agent alone would be only bacteriostatic. The double-strength (DS) formulation is designed for adult and adolescent patients. Listed on the WHO Essential Medicines List, co-trimoxazole is a cornerstone of affordable antibiotic therapy in Bangladesh, used for community-acquired infections, HIV-related prophylaxis, and specific endemic infections including shigellosis and typhoid.

Mechanism of Action: Sequential Folate Pathway Blockade

Co-trimoxazole achieves its antibacterial effect by sequentially blocking two enzymes in bacterial folate biosynthesis. Sulfamethoxazole, a sulfonamide, competitively inhibits dihydropteroate synthase (DHPS), preventing incorporation of para-aminobenzoic acid (PABA) into dihydrofolic acid — the first step in the pathway. Trimethoprim then inhibits dihydrofolate reductase (DHFR), blocking conversion of dihydrofolate to tetrahydrofolate — the active folate cofactor essential for purine and thymidine biosynthesis. This dual blockade depletes bacteria of the folate needed for DNA synthesis and replication. Human cells are unaffected because they obtain folate from dietary sources rather than synthesising it de novo, providing the basis for the drug's selective antibacterial toxicity with a wide therapeutic index in patients without folate deficiency.

Clinical Indications in Bangladesh

In the Bangladesh clinical context, Avlotrin DS has a broad range of indications. For urinary tract infections (UTIs), it is widely used empirically, though local resistance surveillance is important before prescribing. In respiratory infections including acute exacerbations of chronic bronchitis and community-acquired pneumonia (where atypical pathogens are not suspected), co-trimoxazole provides cost-effective coverage. Its most critical contemporary role is in Pneumocystis jirovecii pneumonia (PCP) — both treatment and prophylaxis — in HIV-positive patients and other immunocompromised individuals; it remains first-line therapy for this potentially fatal opportunistic infection. Additional indications include toxoplasmosis prophylaxis, shigellosis, typhoid fever (where susceptibility is confirmed), traveller's diarrhoea, and Stenotrophomonas maltophilia infections. In diabetic patients, who are at disproportionately elevated risk of UTIs, skin and soft tissue infections, and immune compromise, co-trimoxazole may be an important treatment option following appropriate sensitivity testing.

Dosage and Administration

For adults and adolescents over 12 years, the standard dose of Avlotrin DS is one tablet (Trimethoprim 160 mg + Sulfamethoxazole 800 mg) twice daily, taken 12 hours apart. For severe or complicated infections, the physician may increase the dose. Typical treatment duration ranges from 5–14 days depending on the infection type and clinical response. For PCP treatment, high-dose therapy (15–20 mg/kg/day of trimethoprim component) for 21 days is required and must be specialist-supervised. For PCP prophylaxis, one DS tablet daily or three times weekly is standard practice in eligible patients. The tablets should be taken with food or a full glass of water to minimise gastrointestinal intolerance. Patients should maintain adequate hydration throughout the treatment course to prevent crystalluria. Dose reduction is required in renal impairment (CrCl below 30 mL/min). Diabetic patients with nephropathy require particularly careful dose adjustment and renal monitoring.

Important Drug Interactions — Especially for Diabetic Patients

Co-trimoxazole carries several clinically relevant drug interactions that are particularly important for patients with diabetes and associated comorbidities. Trimethoprim inhibits renal tubular secretion of creatinine via OCT2 transporters, which can raise serum creatinine by 10–20% without reflecting genuine GFR decline — a pharmacological effect that must not be misinterpreted as renal deterioration in diabetic nephropathy monitoring. Co-trimoxazole strongly potentiates warfarin via CYP2C9 inhibition, requiring close INR monitoring in anticoagulated patients. In combination with ACE inhibitors, ARBs, or potassium-sparing diuretics — medications widely used in diabetic patients with hypertension and nephropathy — co-trimoxazole can precipitate dangerous hyperkalaemia through trimethoprim's amiloride-like effect on ENaC sodium channels in the distal nephron. Sulfonylurea-induced hypoglycaemia may be potentiated through protein-binding displacement and CYP2C9 inhibition. Metformin-treated patients on co-trimoxazole require monitoring given the drug's impact on creatinine reporting. Complete medication reconciliation is mandatory before prescribing.

Contraindications and Precautions

Avlotrin DS is contraindicated in documented hypersensitivity to trimethoprim, sulfonamides, or any formulation component, including patients with prior sulpha drug allergy. It is contraindicated in severe renal failure (CrCl below 15 mL/min) without dialysis support, severe hepatic impairment, megaloblastic anaemia due to folate deficiency, and in neonates due to the risk of kernicterus from sulphonamide displacement of bilirubin from albumin. Use during pregnancy — particularly the first trimester (folate antagonism and neural tube defect risk) and at term (neonatal hyperbilirubinaemia risk) — should be avoided unless clinically essential. In patients with G6PD deficiency, haemolytic anaemia may occur. Special caution is required in elderly patients, patients with pre-existing renal or hepatic dysfunction, those with blood dyscrasias, and in populations with nutritionally compromised folate status.

Adverse Effects and Patient Monitoring

Common adverse effects of co-trimoxazole include gastrointestinal complaints — nausea, vomiting, anorexia, and diarrhoea — which are reduced by taking the medication with food. Dermatological reactions are of particular concern: mild urticaria and rash may progress to severe and potentially life-threatening Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN), and any new skin eruption during co-trimoxazole therapy warrants immediate medical assessment and drug discontinuation. Haematological adverse effects include thrombocytopenia, leucopenia, and megaloblastic anaemia, particularly with prolonged use or in patients with pre-existing folate deficiency; periodic full blood count monitoring is recommended for courses exceeding two weeks. Hyperkalaemia, through trimethoprim's potassium-retaining mechanism, is an important adverse effect in patients with renal impairment or concurrent potassium-elevating medications. Raised serum creatinine without true GFR decline is expected and should be documented rather than triggering unnecessary dose reduction or drug discontinuation.

Co-trimoxazole Resistance in Bangladesh

Resistance to co-trimoxazole among common Gram-negative pathogens in Bangladesh has risen substantially over recent decades. Community-acquired uropathogenic Escherichia coli strains exhibit resistance rates exceeding 60% in some studies, driven by plasmid-mediated resistance genes including sul1, sul2, and multiple dfrA gene variants. Resistance among Haemophilus influenzae and some Streptococcus pneumoniae isolates is also prevalent. These trends necessitate culture and sensitivity testing before relying on co-trimoxazole for empirical UTI treatment in clinical practice. However, for Pneumocystis jirovecii pneumonia — where the organism cannot be cultured in vitro — clinical resistance to high-dose co-trimoxazole remains relatively infrequent compared to other organisms, preserving its first-line PCP status. Antibiotic stewardship including completing prescribed courses fully, avoiding self-medication, and restricting use to confirmed indications is essential to preserve efficacy in the community.

Storage, Dispensing, and Regulatory Status

Avlotrin DS tablets should be stored at room temperature below 30°C, protected from direct sunlight, heat, and moisture. Keep out of reach of children. Do not use after the printed expiry date. Dispense in original blister packaging. As a prescription-only antibiotic, Avlotrin DS requires a valid prescription from a registered medical practitioner in Bangladesh. Pharmacists should counsel patients at dispensing on completing the full treatment course, maintaining adequate fluid intake, avoiding alcohol during therapy, recognising early warning signs of adverse skin reactions, and never sharing antibiotics or using leftover courses for new symptoms without medical consultation.

Frequently Asked Questions (FAQ)

Q1: What infections is Avlotrin DS used to treat?
A: Avlotrin DS is used for urinary tract infections, respiratory infections, Pneumocystis jirovecii pneumonia (PCP) treatment and prophylaxis in immunocompromised patients, shigellosis, typhoid fever (where susceptible), and other bacterial infections as directed by a physician.

Q2: Is Avlotrin DS safe for diabetic patients taking sulfonylureas or ACE inhibitors?
A: Co-trimoxazole can potentiate hypoglycaemia from sulfonylureas and cause dangerous hyperkalaemia when combined with ACE inhibitors, ARBs, or potassium-sparing diuretics. Diabetic patients must review all their medications with their doctor before taking co-trimoxazole.

Q3: Why does co-trimoxazole cause a rise in creatinine without damaging the kidneys?
A: Trimethoprim inhibits the tubular secretion of creatinine (via OCT2 transporters), raising serum creatinine by 10–20% without reducing actual GFR. This is a predictable pharmacological effect that reverses when the drug is stopped and does not represent true renal injury.

Q4: How many days do I need to take Avlotrin DS?
A: Duration depends on the infection: 3–7 days for uncomplicated UTIs, 7–14 days for respiratory infections, and 21 days for PCP treatment (specialist-supervised). Always complete the full prescribed course even if symptoms resolve earlier — stopping prematurely contributes to antibiotic resistance.

Medical Disclaimer: This information is provided for educational purposes only and does not constitute medical advice. Always consult a qualified physician or pharmacist before starting or changing any medication. DiabetesStore.com.bd does not assume liability for clinical decisions based on this content.