IRENAT Oral drops Ref.[50324] Active ingredients: Sodium perchlorate

Regular and repeated monitoring of thyroid function is necessary during antithyroid therapy so as to allow adjustment of the dosage of Irenat drops to the patient’s changing metabolism and to avoid overtreatment, which might lead to growth of a goitre and symptoms of hypothyroidism. There is a particular risk of adverse consequences of an inappropriately high dose in the case of intrathoracic goitre. All patients must be informed of the need for regular monitoring of blood count.

Falsely low concentrations of ionised calcium may be measured while using Irenat drops as a result of interference with the electrolyte electrode of blood gas analysers.

Uptake of radioiodine or 99mTc-pertechnetate is dose-dependently inhibited by perchlorate. The ability of TSH to stimulate radioiodine uptake is not affected by perchlorate.

If perchlorate is used concomitantly with propylthiouracil or thiamazole/carbimazole as antithyroid therapy, the antithyroid effect is enhanced, as the sites of action of the sodium perchlorate and the thiourea derivatives are different.

Concomitant administration of thiamazole causes a positive perchlorate discharge test (even in patients with hyperthyroidism and healthy subjects) as a result of inhibition of iodine organification.

Concomitant administration of iodine (e.g. iodine-containing medicines or radiographic contrast agents, perioperative use of high-dose iodide) reduces the effect of Irenat drops.

Irenat drops should not be taken during pregnancy, as insufficient experience is available regarding a possible risk to the unborn child. Irenat drops cross the placenta to the fetus unhindered. The fetal thyroid gland may react more sensitively to antithyroid drugs than an adult thyroid.

No studies are available on secretion of sodium perchlorate in breast milk. If treatment with Irenat drops is necessary during lactation, breast-feeding should be ceased.

None known.

Evaluation of undesirable effects is based on the following frequencies: common (≥1% to <10%), uncommon (≥0.1% to <1%), rare (≥0.01% to <0.1%), very rare (<0.01% or unknown).

The occurrence of undesirable effects is dose-dependent.

Common (≥1% to <10%):

• transient rash,
• nausea or retching,
• dry mouth, pharyngeal irritation,
• lymphadenopathy,
• leukopenia,
• purpura,
• febrile arthralgia,
• drug fever.

Uncommon (≥0.1% to <1%):

• initial diarrhoea,
• mild muscle cramps,
• burning in the feet,
• heavy-headedness,
• eosinophilia,
• pruritus,
• jaundice.

An uncommon occurrence is agranulocytosis, which usually resolves rapidly and without sequelae on discontinuing Irenat drops.

Very rare (<0.01%):

• agranulocytosis with a fatal outcome,
• thrombocytopenia or aplastic anaemia with a fatal outcome (incidence approximately 0.1%),
• minimal albuminuria,
• nephrotic syndrome, partially or fully reversible,
• hair loss,
• acne,
• generalised dermatitis,
• urticaria,
• liver damage with acute liver failure,
• erythema nodosum with febrile episodes, antinuclear and anti-erythrocyte antibodies and eosinophilia,
• perforation of a duodenal ulcer.

These extremely rare changes have usually been observed during ongoing treatment with perchlorate, although a causal association could not be proven.

None known.

Miscellaneous

Irenat drops should be discontinued at least 3 days prior to thyroid scintigraphy or measurement of radionuclide uptake.

Use during pregnancy and lactation: see section 4.6.