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Pregnancy and Lactation
OROXINE has been taken by a large number of pregnant women and women of childbearing age without any form of definite disturbances in the reproductive process having been observed so far. Thyroid hypo- or hyperactivity in the mother may, however, unfavourably influence the fetal outcome or well-being. Thyroxine is excreted in breast milk in low concentrations and this may be sufficient to interfere with neonatal screening for hypothroidism.
Effects on Ability to Drive and Use Machines
From the pharmacokinetic and pharmacodynamic properties of thyroxine,
treatment with OROXINE would not be expected to interfere with ability to drive or
operate machinery.
Adverse Reactions
The following effects are indicative of excessive dosage and usually disappear on reduction of dosage or withdrawal of treatment for a few days:
Anginal pain, cardiac arrhythmias, palpitation, cramps in skeletal muscle, tachycardia, diarrhoea, vomiting, tremors, restlessness, excitability, insomnia, headache, flushing, sweating, excessive loss of weight and muscular weakness. Rarely hypersensitivity reactions such as skin rash and pruritus have been reported.
Rare cases of pseudotumour cerebri (benign intracranial hypertension) have been reported, especially in children.
Overdose
In addition to exaggeration of side effects the following symptoms may be seen: agitation, confusion, irritability, hyperactivity, headache, sweating, mydriasis, tachycardia, arrhythmias, tachypnoea, pyrexia, increased bowel movements and convulsions. The appearance of clinical hyper-thyroidism may be delayed for up to five days.
Gastric lavage or emesis is required if the patient is seen within several hours of taking the dose.
Treatment is symptomatic, and tachycardia has been controlled in adults by 40 mg doses of propranolol given every 6 h and other symptoms by diazepam and/or chlorpromazine as appropriate.
PHARMACOLOGICAL PROPERTIES
Thyroxine (T4) is a naturally occurring hormone produced by the thyroid gland and converted to the more active hormone tri-iodothyronine (T3) in peripheral tissues. The precise signals controlling the conversion of T4 to T3 within the cell are not known.
The thyroid hormones are required for normal growth and development, particularly of the nervous system. They increase the resting or basal metabolic rate of the whole organism and have stimulatory effects on the heart, skeletal muscle, liver and kidney. Thyroid hormones enhance lipolysis and the utilization of carbohydrate. 100 micrograms thyroxine is equivalent in activity to 20 to 30 micrograms liothyronine/tri-iodothyronine or 60 mg thyroid BP and/or local pharmacopoeia specification.
Pharmacokinetics
Absorption
Following oral administration, the absorption of thyroxine is incomplete and
variable, especially when taken with food. The amount absorbed increases during
fasting conditions.
Distribution
Thyroxine is nearly totally bound to serum protein.
Metabolism
The main pathway for the metabolism of thyroxine (T4) is its conversion, by de-iodination, to the active metabolite tri-iodothyronine (T3). Further de-iodination of T4 and T3 leads to production of inactive products.
Elimination
Thyroxine is eliminated slowly from the body with a half-life of approximately seven days in a normal person. This may be reduced in hyperthyroid states or increased in hypothyroid patients.
In man, approximately 20 to 40% of thyroxine is eliminated in the faeces and approximately 30 to 55% of a dose of thyroxine is excreted in the urine.
Special Patient Populations
Renal disease and hepatic disease do not appear to have any significant effect on the disposition of thyroxine.
PHARMACEUTICAL PARTICULARS
List of Excipients
Microcrystalline cellulose
Pregelatinised starch
Talc
Colloidal anhydrous silica
Magnesium stearate.
Shelf Life
The expiry date is indicated on the packaging.
Special Precautions for Storage
Do not store above 25°C.
Store in the original container, protected from light.
Keep the container tightly closed.
Nature and Contents of Container
OROXINE Tablets 50mcg and 100mcg are packed into white opaque polypropylene
bottles with tamper-evident, push-fit, low-density polyethylene closures. Each bottle contains 100 tablets.
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