title: A retrospective study on sequential desensitization-rechallenge for antituberculosis drug allergy.
abstract: BACKGROUND
  Antituberculosis (anti-TB) drug allergy often involves multiple concurrently administered drugs which subsequently need to be reinitiated as no better alternatives exist.
  
  
  OBJECTIVE
  To describe the results of tailored sequential desensitization-rechallenge (D-R) for anti-TB drug allergy.
  
  
  METHODS
  Consecutive patients who had undergone D-R to anti-TB drugs between 1 September 1997 and 31 January 2012 were recruited. Following resolution of the acute reaction, anti-TB drug was restarted at 1:6,000 to 1:3 of the final daily dose (FDD), with gradual single or multiple step daily dose escalation to the FDD. Subsequent drugs were sequentially added ≥3 days later when the preceding drug was tolerated. Full blood count and liver function tests were monitored prior to addition of each new drug.
  
  
  RESULTS
  There were 11 patients of whom 10 were male, predominantly Chinese (8 patients). Regimens comprised at least 3 drugs: isoniazid (INH), rifampicin (RIF), ethambutol (EMB), pyrazinamide (PZA), or streptomycin. All patients had nonimmediate reactions, with cutaneous eruptions, where maculopapular exanthema (MPE) was the most common (8 patients). Drug-induced hypersensitivity syndrome (DIHS) occurred in 6 patients, and Stevens Johnson syndrome (SJS) in 2 patients. D-R to INH was successful in 7/9 patients (77.8%) and to RIF/EMB/PZA/streptomycin in all. Of the 2 patients who failed INH D-R, 1 developed fever and MPE on day 3, the other MPE on day 8. D-R with INH and RIF respectively was successful in 2 patients with SJS. Among DIHS patients, 1 failed D-R with INH (fever and MPE on day 3). There were 23/25 (92%) successful D-R among the 11 patients. All patients completed TB treatment of ≥5 months' duration with no cases of drug-resistant TB.
  
  
  CONCLUSIONS
  Tailored sequential TB drug D-R is successful where no better alternative therapies are available, with careful dose escalation and close monitoring, and after a careful risk-benefit assessment.
authors.affiliation: Department of Rheumatology, Allergy and Immunology, Tan Tock Seng Hospital, Singapore 308433, Singapore.
authors.forename: Bernard Yu-Hor
authors.initials: BY
authors.lastname: Thong
authors.affiliation: Department of Rheumatology, Allergy and Immunology, Tan Tock Seng Hospital, Singapore 308433, Singapore.
authors.forename: Faith Li-Ann
authors.initials: FL
authors.lastname: Chia
authors.affiliation: Department of Rheumatology, Allergy and Immunology, Tan Tock Seng Hospital, Singapore 308433, Singapore.
authors.forename: Sze-Chin
authors.initials: SC
authors.lastname: Tan
authors.affiliation: Department of Rheumatology, Allergy and Immunology, Tan Tock Seng Hospital, Singapore 308433, Singapore.
authors.forename: Teck-Choon
authors.initials: TC
authors.lastname: Tan
authors.affiliation: Department of Rheumatology, Allergy and Immunology, Tan Tock Seng Hospital, Singapore 308433, Singapore.
authors.forename: Khai-Pang
authors.initials: KP
authors.lastname: Leong
authors.affiliation: Department of Rheumatology, Allergy and Immunology, Tan Tock Seng Hospital, Singapore 308433, Singapore.
authors.forename: Justina Wei-Lyn
authors.initials: JW
authors.lastname: Tan
authors.affiliation: Department of Rheumatology, Allergy and Immunology, Tan Tock Seng Hospital, Singapore 308433, Singapore.
authors.forename: Chwee-Ying
authors.initials: CY
authors.lastname: Tang
authors.affiliation: Department of Rheumatology, Allergy and Immunology, Tan Tock Seng Hospital, Singapore 308433, Singapore.
authors.forename: Jin-Feng
authors.initials: JF
authors.lastname: Hou
authors.affiliation: Department of Rheumatology, Allergy and Immunology, Tan Tock Seng Hospital, Singapore 308433, Singapore.
authors.forename: Grace Yin-Lai
authors.initials: GY
authors.lastname: Chan
authors.affiliation: Department of Rheumatology, Allergy and Immunology, Tan Tock Seng Hospital, Singapore 308433, Singapore.
authors.forename: Hiok-Hee
authors.initials: HH
authors.lastname: Chng
keywords: Allergy; Desensitization; Drug eruptions; Drug hypersensitivity syndrome
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