Thyrox 50 mcg Tablet

Thyroid hormone replacement for:

• Hypothyroidism (underactive thyroid), including after thyroid surgery or radioiodine
• Congenital hypothyroidism in newborns
• Suppression of TSH in some thyroid cancers and goitre (specialist)

Adults: usually 50–100 mcg daily to start, adjusted every 4–6 weeks by blood tests (TSH) in 12.5–25 mcg steps; typical maintenance 100–200 mcg daily (about 1.6 mcg/kg).

Elderly, heart disease, long-standing hypothyroidism: start 12.5–25 mcg daily and increase slowly.

Newborns/children: dose per kg by specialist (newborns 10–15 mcg/kg/day).

Pregnancy: dose usually needs increasing by 25–30% as soon as pregnancy is confirmed.

• Take once daily on an empty stomach, 30–60 minutes before breakfast (or at bedtime 3 hours after the last meal), with water, at the same time every day.
• Usually lifelong; do not stop without advice.

• Untreated adrenal insufficiency (correct with steroids first)
• Untreated thyrotoxicosis
• Acute heart attack, acute myocarditis
• Use for weight loss (dangerous at high doses)

Side effects usually mean the dose is too high (symptoms of overactive thyroid):

• Fast or irregular heartbeat, palpitations, chest pain (angina)
• Tremor, nervousness, insomnia, sweating, heat intolerance
• Weight loss, diarrhoea, headache, muscle cramps, menstrual changes
• Long-term over-replacement: osteoporosis, atrial fibrillation

Rare: allergic reactions to tablet ingredients; temporary hair loss in children.

• Check TSH 6–8 weeks after starting or changing dose, then yearly.
• Heart disease, elderly: start low.
• Diabetes: sugar control may change.
• Keep the same brand if possible (switching brands can change levels).

Essential to continue in pregnancy — untreated hypothyroidism harms the baby; dose usually increased with monthly TSH checks. Safe while breastfeeding.

Reduce absorption — take 4 hours apart: calcium, iron, antacids, sucralfate, cholestyramine, orlistat, PPIs (long-term), soy and high-fibre foods, coffee (take at least 30–60 minutes later).

• Warfarin (increased effect — monitor INR)
• Diabetes medicines (may need higher doses)
• Rifampicin, carbamazepine, phenytoin (increase levothyroxine needs)
• Oestrogens/oral contraceptives (may increase dose needs)
• Amiodarone, lithium (thyroid effects)

Fast heartbeat, agitation, fever, tremor, chest pain, seizures (may appear after several days). Seek medical care.

Store below 25–30°C in the original pack, protected from light and moisture.