How does it work?
Navidrex tablets contain the active ingredient cyclopenthiazide, which is a type of medicine called a thiazide diuretic. Diuretics are sometimes referred to as 'water tablets'. They remove excess fluid from the body by increasing the production of urine.
Diuretics act in the kidneys. They work by causing the kidneys to increase the amount of salts, such as potassium and sodium, that are filtered out of the blood and into the urine. When these salts are filtered out of the blood by the kidneys, they draw water alongside them. As diuretics increase the removal of salts from the blood, they also cause more water to be drawn out of the blood and into the urine.
Removing water from the blood decreases the volume of fluid circulating through the blood vessels. This subsequently decreases the pressure within the blood vessels. Diuretics such as cyclopenthiazide can therefore be used to lower high blood pressure.
Cyclopenthiazide is also used to treat conditions where excess fluid has been retained in the body (oedema). For example, in heart failure, the pumping mechanism of the heart is less effective. This can cause fluid to build up in the ankles and the lungs (pulmonary oedema), which makes it difficult to breathe. Cyclopenthiazide helps the body to remove this excess fluid. Removing fluid from the blood vessels also decreases the pressure within the blood vessels. This makes it easier for a weak heart to pump blood around the body.
Cyclopenthiazide is also used to remove excess fluid retention (oedema) caused by conditions such as kidney disease, liver cirrhosis and pre-menstrual syndrome.
What is it used for?
- High blood pressure (hypertension).
- Mild to moderate stable, chronic heart failure.
- Excess fluid retention (oedema) due to kidney disease.
- Excess fluid collection in the abdomen (ascites) due to cirrhosis of the liver.
- Excess fluid retention (oedema) in pre-menstrual syndrome.
How do I take it?
- Navidrex tablets can be taken either with or without food.
- Navidrex tablets should be swallowed with a drink of water. The number of tablets to take daily depends on the condition being treated. Follow the instructions given by your doctor. These will be printed on the dispensing label your pharmacist has put on the packet of medicine.
- As diuretics cause your kidneys to produce more urine, you may find that if you take a dose too late in the day that you need to get up in the night to visit the toilet. For this reason, it is recommended that you take this medicine in the morning. Seek further advice from your doctor or pharmacist.
- This medicine may cause fatigue and dizziness. You should take care when performing potentially hazardous activities, such as driving or operating machinery, until you know how this medicine affects you and are sure you can perform such activities safely.
- Alcohol may enhance the blood pressure lowering effect of this medicine, which could cause dizziness or fainting. Take extra care if you drink alcohol while you are taking this medicine.
- While taking this medicine you may need to have regular blood tests to monitor your kidney function and the levels of salts such as potassium and sodium in your blood.
- If you experience any of the following symptoms while taking this medicine you should inform your doctor promptly, so that the amount of fluids and salts in your body can be checked: thirst, lethargy, confusion, weakness, drowsiness, muscle cramps, scanty production of urine, abnormal heart rhythm, seizures, nausea and vomiting.
- Cyclopenthiazide can sometimes cause the level of sodium in your blood to fall too low and, for this reason, following a very strict low salt (sodium) diet should be avoided while you are taking this medicine.
Use with caution in
- Elderly people.
- Kidney disease.
- Liver disease.
- People with a history of high levels of uric acid in their blood or gout.
- People with high levels of fats (lipids) such as cholesterol and triglycerides in the blood (hyperlipidaemia).
- A condition called systemic lupus erythematosus, which involves long-term inflammation of some internal organs.
- People on a low salt (sodium) diet.
- People who are malnourished.
Not to be used in
- Severe kidney failure.
- Severe liver disease.
- People allergic to thiazide diuretics.
- People allergic to medicines from the sulphonamide group, eg the antibiotic sulfamethoxazole.
- People with a high level of calcium in their blood (hypercalcaemia).
- People with low levels of potassium or sodium in their blood (hypokalaemia or hyponatraemia).
- People with inadequate production of natural steroid hormones by the adrenal glands (Addison's disease).
- This medicine is not recommended for children and adolescents under 18 years old.
This medicine should not be used if you are allergic to any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.
If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.
Pregnancy and breastfeeding
Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.
- This medicine should not normally be used during pregnancy. Thiazide diuretics can reduce placental blood flow to the baby and, if used in the second or third trimester, can cause problems such as jaundice, low platelet count and disturbances in the baby's electrolyte levels. This medicine should not be used to treat high blood pressure in pregnancy or fluid retention in otherwise healthy pregnant women. It should only be used in other situations if considered essential by your doctor. The expected benefit to the mother must be greater than the possible risks to the developing baby. Seek further medical advice from your doctor.
- Cyclopenthiazide passes into breast milk and could have unwanted effects on a nursing infant. In high doses it can also reduce the production of breast milk. This medicine is not recommended for women who are breastfeeding. Seek further medical advice from your doctor.
Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.
- Disturbances of the gut such as diarrhoea, constipation, nausea, vomiting or abdominal pain.
- Loss of appetite.
- A drop in blood pressure that occurs when going from lying down to sitting or standing, which results in dizziness and lightheadedness (postural hypotension).
- Increased need to pass urine.
- Decreased level of potassium in the blood (hypokalaemia).
- Rise in the levels of fats such as cholesterol in the blood.
- Decreased level of sodium in the blood (hyponatraemia).
- Increased level of calcium in the blood (hypercalcaemia).
- Increased level of glucose in the blood (hyperglycaemia).
- Increased level of uric acid in the blood (hyperuricaemia) - this may cause kidney problems and gout.
- Skin reactions such as rash, increased sensitivity to sunlight (photosensitivity).
- Sensation of pins and needles.
- Disturbed sleep.
- Visual disturbances.
- Erectile dysfunction (impotence)
- Disturbance in the normal numbers of blood cells in the blood.
- Abnormal heart beats (arrhythmias).
The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.
For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.
How can this medicine affect other medicines?
It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to make sure that the combination is safe.
This medicine is likely to have an additive effect with other medicines that decrease blood pressure, particularly medicines that are used to treat high blood pressure (antihypertensives). This may cause dizziness, which can usually be relieved by lying down until the symptoms pass. If you feel dizzy while taking this medicine in combination with other medicines that can lower blood pressure you should let your doctor know, as your doses may need adjusting. Other medicines that decrease blood pressure include the following:
- ACE inhibitors, eg enalapril
- alpha-blockers such as prazosin
- angiotensin II receptor antagonists such as losartan
- antipsychotics such as chlorpromazine
- benzodiazepines, eg temazepam, diazepam
- beta-blockers such as propranolol
- calcium-channel blockers such as verapamil, nifedipine
- other diuretics, eg furosemide (if this medicine is used with other diuretics there may also be a greater chance of the level of sodium or potassium in your blood falling too low)
- dopamine agonists, eg bromocriptine, apomorphine
- MAOI antidepressants, eg phenelzine
- nitrates, eg glyceryl trinitrate
This medicine reduces the ability of the body to remove the medicine lithium. As this can increase the blood level of lithium and the risk of its side effects, this medicine should not be taken by people taking lithium.
Cyclopenthiazide can decrease the amount of potassium in the blood. If it is used in combination with any of the following medicines, which can also lower potassium in the blood, the risk of a low blood potassium level (hypokalaemia) is increased:
- corticosteroids, such as hydrocortisone and prednisolone
- beta 2 agonists, eg salbutamol, terbutaline
- other diuretics, eg furosemide
If the level of potassium in your blood falls during treatment, this can increase the risk of side effects on the heart caused by the following medicines:
- medicines for abnormal heart rhythms (antiarrhythmics), eg amiodarone, flecainide, sotalol, disopyramide
- certain antipsychotic medicines, eg amisulpride, sertindole, pimozide.
Diuretics can sometimes increase blood glucose levels and people with diabetes may therefore need increases in their dose of insulin or antidiabetic tablets while taking this medicine. If you have diabetes you should talk to your doctor about this. You may need to monitor your blood sugar levels more frequently.
Cyclopenthiazide can increase the amount of calcium in your blood. If you are taking calcium or vitamin D supplements, or regularly take large amounts of calcium-containing antacids, your doctor may want to monitor the level of calcium in your blood to make sure it doesn't rise too high. Taking occasional antacids with Navidrex should not cause any problems.
Colestyramine and colestipol can reduce the absorption of cyclopenthiazide from the gut. if you have been prescribed either of these medicines you should not take them within four hours of taking Navidrex.
There may be an increased risk of allergic reactions to allopurinol in people taking thiazide diuretics such as cyclopenthiazide, particularly if they also have any kidney problems.
The following medicines may reduce the diuretic and blood pressure lowering effect of this medicine:
- corticosteroids, such as dexamethasone or prednisolone
- oestrogens, such as those in the contraceptive pill
- regular use of non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, diclofenac or indomethacin (occasional painkilling doses are unlikely to have a significant effect). Diuretics such as this one also increase the chance of side effects on the kidneys that can be caused by NSAIDs.
Other medicines containing the same active ingredient
There are currently no other medicines available in the UK that contain cyclopenthiazide as the sole active ingredient.
Navispare tablets contain cyclopenthiazide in combination with the potassium-sparing diuretic amiloride.