title: Does tachyphylaxis occur in long-term management of scalp seborrheic dermatitis with pyrithione zinc-based treatments?
abstract: BACKGROUND
  Scalp seborrheic dermatitis and dandruff (SD/D) are chronic conditions requiring long-term treatment. There is a common belief that patients frequently experience decreasing benefits over time when using a single product. This physiologic accommodation is termed tachyphylaxis.
  
  
  OBJECTIVE
  To systematically investigate the anecdotal belief that tachyphylaxis occurs in long-term treatment of SD/D using quantitative clinical assessments.
  
  
  METHODS
  An international questionnaire completed by 722 dermatologists assessed the belief of tachyphylaxis incidence with pyrithione zinc (PTZ)-based shampoos, time course, occurrence relative to active ingredients, and effect of switching products. Two double-blind, randomized, clinical evaluations were conducted, 24- and 48-week studies, whereby a 1% PTZ shampoo, a 2% PTZ shampoo, or a matched placebo control shampoo was used by each subject for the duration of the study. Dermatologists assessed the adherent scalp flaking (scale of 0-10) at baseline and at specified intervals.
  
  
  RESULTS
  Sixty-four per cent of responding dermatologists believed tachyphylaxis occurred with PTZ products, and most felt that tachyphylaxis occurred within 3 months of use. Evaluation of mean treatment responses vs. placebo and individual responses as a function of study duration showed a consistent benefit for all products at all time points; therefore, no evidence for tachyphylaxis was found (within 48 weeks of treatment).
  
  
  CONCLUSIONS
  No evidence for tachyphylaxis in SD/D treatment by PTZ-based shampoos was found. Compliance could explain the decreasing response rate seen over time; the solution is to choose an affordable therapeutic product that is effective long term without cosmetic trade-offs.
authors.affiliation: Beauty Care Product Development, The Procter & Gamble Company, Cincinnati, Ohio 45241, USA. Schwartz.jr.2@pg.com
authors.forename: James R
authors.initials: JR
authors.lastname: Schwartz
authors.forename: Heather
authors.initials: H
authors.lastname: Rocchetta
authors.forename: Pravit
authors.initials: P
authors.lastname: Asawanonda
authors.forename: Fangyi
authors.initials: F
authors.lastname: Luo
authors.forename: Jennifer H
authors.initials: JH
authors.lastname: Thomas
mesh_terms: D000287:Administration, Topical; D012628:Dermatitis, Seborrheic / Q000175:diagnosis / Q000188:drug therapy*; D003880:Dermatology; D005260:Female; D006203:Hair Preparations / Q000009:adverse effects*; D006801:Humans; D015994:Incidence; D008134:Long-Term Care; D008297:Male; D015337:Multicenter Studies as Topic; D009942:Organometallic Compounds / Q000009:adverse effects* / Q000627:therapeutic use; D011725:Pyridines / Q000009:adverse effects* / Q000627:therapeutic use; D018570:Risk Assessment; D012536:Scalp Dermatoses / Q000175:diagnosis / Q000188:drug therapy*; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires; D013618:Tachyphylaxis; D013997:Time Factors
chemical_list: D006203:Hair Preparations; D009942:Organometallic Compounds; D011725:Pyridines; C010423:pyrithione zinc