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 presecription 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) Non-surgical treatment

Although tablets are available for patients with recurrent cystine stones, these are only required in the minority of patients. They are very specialised medications and should only be started under the guidance of a hospital specialist with monioring by your general practitioner (GP). They act by combining with cystine (by attaching at the disulphide bond - see ...tell me more) to form a more soluble compound (complex) that is more soluble 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:
  • Tiopronin (Drug name: alpha mercaptopropionylglycine, Trade name examples: Thiola and Acadione)
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. The drug information leafelt for thiola (produced by Mission Pharmacal Company, San Antonio) can be downloaded at the bottom of this page.
  • D-penicillamine (Trade name: Distamine)
Penicillamine is an older medication than tiopronin and is associated with more side effects which means that a higher proportion of patients have to stop the medication. The dose varies between 1 - 3g per day in divided doses.
  • Captopril (Trade name: Capoten)
Captopril is usually only used if the other medications are unsuitable. It is an old medication for the treatment of high blood pressure and belongs to a class of medications known as ACE inhibitors. It is not commonly used as there is debate in the medical literature about its effect on reducing cystine levels in the urine and stone prevention.

Disclaimer and Copyright
vBulletin stats
Ċ
Matthew Bultitude,
5 Apr 2010, 13:18