Classification of Drugs

Code	Interpretation
NP	Not porphyrinogenic Used as a first-line choice. No precautions needed.
PNP	Probably not porphyrinogenic Used as a first-line choice. No precautions needed.
PSP	Possibly porphyrinogenic Only use when no safer alternatives are available. Precautions motivated in vulnerable patients.
PRP	Probably porphyrinogenic Prescribe only on strong or urgent indications. Precautions motivated in all patients.
P	Porphyrinogenic Prescribe only on urgent indications. Precautions should be taken in all patients.
NC	Not yet classified Not yet classified as safe and should be avoided. Prescribe only on strong indication when no safer alternatives are available. Seek advice from a porphyria specialist.