Unlicensed Iopanoic acid

You have thyrotoxicosis (thyroid over-activity) which we are considering treating with a medication called iopanoic acid. We use iopanoic acid when the other treatments available for thyrotoxicosis have not been successful in normalising thyroid hormones, or cannot be used because of dangerous side effects. It is important that we bring your thyroid hormones under control as quickly as possible, either because the thyrotoxicosis is having an adverse effect on your general health, and/or because your doctor would like to treat you with thyroidectomy (surgery to remove the thyroid) for reasons which will have been discussed with you. Thyroidectomy can be extremely hazardous if performed in individuals whose thyrotoxicosis is not adequately controlled.

You have tried several other medicines to treat your thyrotoxicosis that have either not worked or have been stopped due to dangerous side effects. At this time there is no other medication which we could use instead of iopanoic acid to normalise your thyroid hormones quickly, so your doctor has recommended iopanoic acid as the most appropriate medicine to treat your thyrotoxicosis.

What is iopanoic acid?

Iopanoic acid is a medication which previously was used in hospitals for patients undergoing scans of the gallbladder. However, an additional effect of iopanoic acid is to decrease thyroid hormone levels, and its effects last for around 2 weeks. We have found this very effective for ensuring that thyroid hormone levels are safe in time for thyroid surgery, in patients in whom standard thyroid medications have not worked or cannot be used because of dangerous side effects. Other endocrine centres have also used iopanoic acid for thyrotoxicosis in the past.

The manufacturer of licensed iopanoic acid tablets stopped production many years ago for commercial reasons, so iopanoic acid is no longer widely used in medical practice. The only iopanoic acid product available at the present time is an unlicensed ‘laboratory grade’ product because it is no longer manufactured under license by the standard pharmaceutical companies which supply medications to NHS hospitals.

What is a ‘laboratory grade’ product?

Licensed medicines are manufactured by pharmaceutical companies under a set of conditions called ‘Good Manufacturing Practice’. The manufacturer of laboratory grade iopanoic acid does not intend iopanoic acid to be used as a medicine, so they do not manufacture under a licence and so is an unlicensed medicine.

However there are assurances that this product meets some of the requirements for oral medicines made under Good Manufacturing Practice, including purity. We have used laboratory grade iopanoic acid for many years at Addenbrooke’s and we have lots of experience using laboratory grade iopanoic acid as a medicine.

Iopanoic acid can only be prescribed by specialists in hospital and it cannot be prescribed by your GP.

How do I take laboratory grade iopanoic acid?

Before we start treatment with iopanoic acid we will ask you to sign a consent form specifically consenting to using laboratory grade iopanoic acid and the medicine being unlicensed. We will add this to your hospital records.

Laboratory grade iopanoic acid does not look like a normal medicine like a tablet or syrup, rather it is dispensed as a powder measured out into bottles that each contain one dose of 500mg.

The powder is mixed with water and swallowed; if there is any powder left stuck to the inside of the bottle, keep adding water, mixing and swallowing until there is no powder left. We find it usually takes at least two rounds of mixing with water to get all of the powder out of the bottle. Most patients find that the powder mixed with water does not have a taste at all.

We are particularly cautious in how we administer iopanoic acid; specifically we will give a small test dose (50mg) and observe you for an hour to check for any adverse reaction. If you are well, we usually then prescribe 500mg iopanoic acid two or three times a day. It is usually given as a short course of several days to one or two weeks, to prepare you for thyroidectomy.

What are the side effects of iopanoic acid?

• Most patients do not experience side effects from iopanoic acid, and it has been well tolerated by patients we have treated in the past.
• However, as with any medication, mild side effects may occur like nausea, heartburn or constipation. If these symptoms occur, we may be able to prescribe an antacid or laxative medication to help.
• Other rare side effects have been reported with iopanoic acid when it was used for scans of the gallbladder. It has been known to affect liver or kidney function and rarely to cause a decrease in the number of blood cells involved in blood clotting (platelets). These effects are extremely rare, but we will check blood tests before commencing iopanoic acid and during the course of treatment, to detect any such adverse consequences.

Please contact the numbers below if you have any concerns or need any further information.

Contact us

01223 217848 Endocrine Nurse Office

01223 216218 Endocrine Secretary

01223 217502 Pharmacy Medicines Information