Prevention

It is important to emphasise the importance of the basic measures (such as increasing fluid intake) to patients with cystinuria as a very simple way of self-help. Patients must drink enough so the daily output should be between 2 to 3 litres. It is often necessary to wake in the night to drink water.

1) Increase fluid intake - This is covered extensively in 'What can I do ?' 'Diet...tell me more'. All patients must do this to dilute their urine to prevent and minimise stone formation.

2) Modify Diet - see 'Diet - what should I eat ?'.

3) Alkalinisation of urine  - This can be vital as by making the urine less acidic, cystine becomes more soluble and therefore less likely to form stones. The graph shows how the concentration of cystine needed to form crystals rises dramatically as the pH of the urine increases.

The pH (acidity) of the urine should be measured at regular intervals to check on progress, to ensure that the treatment is working and to ensure that the urine does not become too alkaline i.e. pH>7.5 as this can promote other types of stones (calcium phosphate). Measurements can be made easily by the patient at home using specialised pH sticks. To alkalinise the urine we normally use potassium citrate liquid (Note: This should only be done under the instruction and supervision of a doctor). Sodium bicarbonate has been used in the past although the high sodium content may cause other stones to form - therefore we would not recommend it. Potassium citrate liquid can be unpalatable for many patients - tablets are available in the USA but currently only on special prescription in the UK (and is therefore very difficult to get hold of).Once on treatment, the pH (acidity) of the urine should be measured at regular intervals to monitor response, to ensure that the treatment is working and to ensure that the urine does not become too alkaline as this would promote other types of stones. Measurements can easily be made at home using specialised pH sticks.

4) Chelating agents - These are a class of drug that reduce the cystine concentration in the urine and reduces the risk of stone formation. These are not required in all patients with cystinuria. They are very specialised medications and should only be started under the guidance of a hospital specialist with monitoring by your specialist or general practitioner (GP). They act by breaking the cystine molecule (at the disulphide bond - see ...tell me more) into 2 more soluble compounds (cysteine) and binding to it to prevent it reforming cystine. This is 50 times more soluble than cystine and therefore more easily excreted in the urine. The decision as to when to start a tablet will be different for individual patients but will usually depend on the frequency of stone formation, need for surgical treatment and response to more conservative measures, for example, increasing fluids, alkalinisation and diet. 

The main drugs that are used are:

This is the most commonly used due to having fewer side effects than the older medication penicillamine. It is a tablet that is usually taken three times per day. The dose depends on cystine levels in the urine and how well it is tolerated, but a common dose is 1000mg/day in divided doses. Tiopronin is unlicensed in the UK and is imported from other countries with which the UK has a mutual agreement on standards of licensing. Your doctor, nurse or pharmacist can give you more information on the use of unlicensed medicines. Further information about tiopronin can be found here: FDA information on tiopronin or on the company website

Penicillamine is an older medication than tiopronin. Historically it has been thought to be associated with higher side-effects although that difference is marginal and has not necessarily been our experience. The dose varies between 1 - 3g per day in divided doses. Further information about penicilliamine can be found here: British National Formulary - Penicillamine or on the company website.

Captopril is an old medication for the treatment of high blood pressure and belongs to a class of medications known as ACE inhibitors. It was used if other medications are not tolerated. However recent evidence suggests that it is not effective in the prevention of cystine stones and so it is no longer recommended by international gudielines.