Hepatic enzyme inducers:

• long term alcohol abuse
• rifampicin
• anticonvulsants, particularly phenytoin, carbamazepine, phenobarbitone and primidone
• spironolactone
• griseofulvin

hepatic enzyme inhibitors:

• alcohol consumed during 'binges'
• antibiotics:
  • isoniazid
  • erythromycin
  • sulphonamides
  • metronidazole
  • chloramphenicol
  • ketoconazol
• anticonvulsants, particularly valproate
• cimetidine
• allopurinol
• chlorpromazine
• imipramine
• propranolol
• metoprolol
• interferon