title: Caffeine consumption and methotrexate dosing requirement in psoriasis and psoriatic arthritis.
abstract: BACKGROUND
  Recent animal and human studies have suggested that the therapeutic benefit of methotrexate in the treatment of rheumatoid arthritis may be substantially reduced in patients who are concomitantly consuming caffeine. Here, we aimed to investigate the effect of caffeine consumption on the methotrexate dosing requirements in patients with psoriasis and psoriatic arthritis.
  
  
  METHODS
  One hundred and fifty patients with diagnoses of psoriasis or psoriatic arthritis were surveyed for their current weekly methotrexate dosage and their usual daily consumption of caffeine.
  
  
  RESULTS
  Seventy-five of the patients given the survey responded; of these, 11 were eliminated because they did not report their methotrexate dosage or were no longer taking methotrexate. Of the remaining 64 patients, no correlation was found between the methotrexate dosage needed for disease maintenance and the amount of caffeine consumed.
  
  
  CONCLUSIONS
  Our findings suggest that caffeine does not affect methotrexate dosage requirements in patients with psoriasis and psoriatic arthritis. These results do not rule out an effect of caffeine in other inflammatory diseases treated with methotrexate.
authors.affiliation: Department of Dermatology, Mayo Clinic, Scottsdale, Arizona 85259, USA. swanson.david@mayo.edu
authors.forename: David L
authors.initials: DL
authors.lastname: Swanson
authors.forename: Sunni A
authors.initials: SA
authors.lastname: Barnes
authors.forename: Stephanie J
authors.initials: SJ
authors.lastname: Mengden Koon
authors.forename: Rokea A
authors.initials: RA
authors.lastname: el-Azhary
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015535:Arthritis, Psoriatic / Q000188:drug therapy*; D002110:Caffeine / Q000494:pharmacology*; D003879:Dermatologic Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D004347:Drug Interactions; D005260:Female; D018565:Food-Drug Interactions; D006801:Humans; D008297:Male; D008727:Methotrexate / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008875:Middle Aged; D011565:Psoriasis / Q000188:drug therapy*
chemical_list: D003879:Dermatologic Agents; D002110:Caffeine; D008727:Methotrexate