TREATMENT OF HYPERTENSION AND HEART FAILURE IN PORPHYRIA

INTRODUCTION

In considering appropriate therapy for these common conditions in patients with porphyria, it is always worthwhile to answer the following question first: How definite is the diagnosis of porphyria? It is not uncommon for people, particularly older people who may have been tested for porphyria many years before, to have been falsely diagnosed as VP: if indeed they do not have porphyria at all, then the choice of therapy becomes much simpler. If in any doubt, have the patient retested.

HYPERTENSION

• Diuretics: Though some thiazides are porphyrinogenic in experimental systems, there is no convincing evidence that they are dangerous in practice and their use in porphyria appears acceptable. Furosemide may be used safely.
  
  
• Beta blockers: All beta blockers are safe in porphyria and their use is recommended.
  
  
• ACE inhibitors: Captopril, enalapril, lisinopril and quinapril are safe. It is likely that the rest of the class are safe as well. We have used both enalapril and ramipril freely in our patients without problem.
  
  
• ARB blockers: In general these appear safe. Eprosartan, candesartan and valsartan should be used in preference to the others. However, some of these, such as losartan, have been used safely in porphyria, and further experience may yet show that all are safe.
  
  
• Calcium channel blockers: In experimental systems, these are highly porphyrinogenic and should therefore be used with extreme caution only - we suggest that ACE inhibitors be used in preference. Nifedipine, verapamil and nitrendipine are all highly inducing: nicardipine less so and diltiazem may be the safest.
  
  
• Others: Prazosin and doxazosin appears safe in practice.
  
  
• Older agents: Reserpine is safe. Methyldopa, hydralazine, dihydralazine and clonidine are dangerous and must be avoided.

HEART FAILURE

• Diuretics: see note above. Furosemide appears safe in practice, as is bumetanide.
  
  
• Digoxin: safe for use.
  
  
• ACE inhibitors: see above.

ANGINA AND ISCHAEMIC HEART DISEASE

• Nitrates: These are safe.
  
  
• Beta blockers: These are safe.
  
  
• ACE inhibitors: Likely to be safe - see note above.
  
  
• Calcium channel antagonists: See note above. Best avoided; if use is essential, diltiazem should be employed with extreme caution.
  
  
• Aspirin: Safe.
  
  
• Heparin and streptokinase: In acute infarction and unstable angina, heparin is safe. Though there are no data on streptokinase or tissue plasminogen activator, these are likely to be safe and may be used with caution.

ANTIARRHYTHMICS

Digoxin and beta blockers are safe. Amiodarone is highly metabolised and there are conflicting reports on its safety. It should be used with extreme caution only. Calcium channel blockers should also be used only with extreme caution. MAny of the older agents are also problematical. Each case should be considered individually.

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