1. Clinical Overview
A fixed-dose combination product containing a low-dose thyroid hormone (Thyroxine) with two B-vitamins (Nicotinamide and Pyridoxine). It is primarily used as a metabolic enhancer and for the supportive treatment of hypothyroidism, particularly in cases associated with nutritional deficiencies or subclinical presentations. The combination aims to address both the endocrine deficiency and potential cofactor deficiencies that may impair energy metabolism.
| Onset | Duration | Bioavailability |
|---|---|---|
| Thyroxine: 3-5 days for metabolic effects; Nicotinamide/Pyridoxine: Hours to days. | Thyroxine: 7-10 days (due to long half-life); Nicotinamide/Pyridoxine: Variable, dependent on nutritional status. | Thyroxine: ~70-80% (fasting); Nicotinamide: >85%; Pyridoxine: ~90%. |
2. Mechanism of Action
Thyroxine (T4) is a prohormone converted to the active Triiodothyronine (T3) in peripheral tissues. It binds to nuclear thyroid hormone receptors, regulating gene expression to increase basal metabolic rate, protein synthesis, and growth/development. Nicotinamide is a precursor to NAD+ and NADP+, coenzymes critical for redox reactions and cellular energy production (glycolysis, TCA cycle). Pyridoxine (B6) is converted to Pyridoxal Phosphate (PLP), a cofactor for over 100 enzymes involved in amino acid, neurotransmitter, and hemoglobin synthesis.
3. Indications & Uses
- Supportive therapy in subclinical hypothyroidism (mild TSH elevation with normal T4)
- Nutritional and metabolic support in convalescence or fatigue states where mild thyroid support is indicated
- Adjuvant in management of certain dermatological conditions (like pellagra, acne) with suspected metabolic component
4. Dosage & Administration
Adult Dosage: One tablet daily, preferably on an empty stomach, 30-60 minutes before breakfast. Dose must be individualized based on clinical response and TSH levels.
Administration: Take with a full glass of water on an empty stomach, at least 30-60 minutes before food, coffee, or other medications (especially calcium, iron, antacids) to ensure optimal absorption of thyroxine. Consistency in timing is crucial.
5. Side Effects
Common side effects may include:
- Mild transient hair loss (especially during initial months of therapy)
- Headache
- Nervousness or irritability
- Insomnia
- Increased appetite
- Gastrointestinal discomfort (nausea)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Calcium Carbonate / Iron Supplements / Antacids | Markedly decrease absorption of Thyroxine | Major |
| Warfarin | Thyroxine may potentiate anticoagulant effect, increasing INR risk | Major |
| Oral Hypoglycemics / Insulin | Thyroxine may alter glycemic control, requiring dose adjustment | Moderate |
| Phenytoin, Carbamazepine, Rifampicin | Increase hepatic metabolism of Thyroxine, reducing its efficacy | Moderate |
| Amitriptyline, SSRIs | Enhanced effects of both drugs; increased risk of arrhythmias | Moderate |
| Digoxin | Thyroxine may decrease serum digoxin levels | Moderate |
| Ketamine | Risk of severe hypertension and tachycardia | Major |
| Levodopa | Pyridoxine may decrease the efficacy of Levodopa (not Carbidopa/Levodopa combinations) | Moderate |
7. Patient Counselling
- DO take the tablet at the same time every day, on an empty stomach, 30-60 min before breakfast.
- DO inform all your doctors and dentists you are taking this medicine.
- DO get your thyroid function (TSH) tested as advised by your doctor.
- DON'T take it with coffee, milk, or food.
- DON'T take calcium/iron supplements or antacids within 4 hours of this medicine.
- DON'T change the dose or stop taking it without consulting your doctor.
8. Toxicology & Storage
Overdose: Symptoms are primarily those of thyrotoxicosis: fever, tachycardia, arrhythmias, hypertension, heart failure, agitation, psychosis, tremors, sweating, diarrhea, weight loss, heat intolerance. Chronic high-dose Pyridoxine (>500mg/day) can cause sensory neuropathy.
Storage: Store below 25°C, in a cool, dry place. Protect from light and moisture. Keep out of reach of children. Do not use after the expiry date printed on the pack.