Medicines and porphyria: safe prescribing in acute porphyria

MedlinePlus separates the cutaneous type, which causes blistering, itching and swelling after sun exposure, from acute porphyria, which affects the nervous system and can cause chest or abdominal pain, muscle problems, vomiting, constipation and mental changes. Drug choice matters mainly in the acute forms, although other medicines can matter in the cutaneous type too.

This page concerns the acute porphyrias. Our wider guides to porphyria and acute intermittent porphyria cover diagnosis, genetics and outlook.

In acute porphyria an enzyme in the heme-making pathway is partly deficient. Some medicines increase demand for heme in the liver and push the pathway harder, so that harmful precursors build up and cause symptoms. The same applies to fasting, infection and alcohol, which is why attacks often have several contributing causes at once.

MedlinePlus says that attacks can be provoked by certain medicines, smoking and alcohol, infections, stress and sun exposure, and that identifying and avoiding triggers is the first line of management. Other approaches include intravenous heme therapy, medicines to relieve symptoms, glucose in acute cases, and hospital care for severe attacks.

The UK Porphyria Medicines Information Service, working jointly with the Cardiff Porphyria Service, describes itself as an advisory service on the safe use of drugs in porphyria for UK healthcare professionals and members of the public. It publishes an annual safe list, in alphabetical and therapeutic arrangements, of medicines considered safe for first-line use in the acute porphyrias.

The service states that inclusion does not guarantee safety in all circumstances, and that all topical preparations on intact skin are considered safe. Because new medicines appear and evidence changes, clinicians should consult the current version rather than an old printout or a memory of what was acceptable years ago.

• Ask the prescriber or pharmacist to check each new medicine against the current UK safe list.

• If a medicine is not on the list, that does not always mean it is unsafe; it may simply be unassessed, so ask for specialist advice.

• Ask for a safe alternative rather than stopping a necessary treatment.

Infections are a trigger in themselves and must be treated, so the question is which antibiotic. Pain needs treatment too, as attacks are painful, and the specialist team can advise on analgesics. Contraception and hormone treatments can matter, as can anti-epileptic drugs and medicines for mood or sleep. Over-the-counter and herbal products need the same check as prescriptions.

Dental treatment and minor procedures usually involve local anaesthetics, and the dentist or surgeon should confirm the product against the safe list. Fasting before a procedure can itself provoke an attack, so ask whether glucose or carbohydrate drinks can be arranged.

Tell the surgical team and the anaesthetist in advance, ideally at pre-assessment, and bring a letter from your porphyria centre if you have one. Anaesthetic drugs differ in safety, and the anaesthetist can choose from agents considered safe. Fasting should be kept short, and carbohydrate intake maintained where possible.

In an emergency, the A&E team may not know the condition. Carry a card or wristband, and have the centre's contact details to hand. Severe abdominal pain with vomiting, confusion, muscle weakness, a racing heart or dark urine in someone with known acute porphyria warrants urgent assessment, by 999 if severe.

The Cardiff service is described as an international expert centre, and UK patients are typically supported by specialist porphyria services and their local metabolic or haematology team. Annual review helps catch new triggers, medication changes and complications.

Family members may also carry the gene without symptoms. Genetic counselling can clarify who is at risk and who should also avoid unsafe drugs. The existing page on porphyria skin signs covers the cutaneous side.