title: Represcription of penicillin after allergic-like events.
abstract: OBJECTIVE
  We sought to determine the frequency of represcription of penicillin to individuals with penicillin allergy and the risk of a second reaction in those who had a previous reaction.
  
  
  METHODS
  A retrospective cohort study was conducted within the UK General Practice Research Database. All patients who had received a prescription for penicillin were identified. Within that source population, records of patients who had received at least 2 prescriptions for penicillin at least 60 days apart were selected and examined for allergic-like (hypersensitivity) events on the day of or within 30 days after a prescription.
  
  
  RESULTS
  At least one prescription for penicillin was given to 3,375,162 patients. Of 6212 (0.18%) patients who experienced an allergic-like event after the initial prescription, 48.5% were given a second prescription compared with 59.8% of those without an initial allergic-like event (risk ratio, 0.81; 95% CI, 0.79-0.83). Two or more prescriptions for penicillin were given to 2,017,957 patients. Three thousand fourteen (0.15%) patients experienced an allergic-like event after the first prescription, and 57 (1.89%) of those had another event after the second prescription. The unadjusted odds ratio of an allergic-like event after the second prescription for those who experienced an allergic-like event after the first prescription, compared with those who had no initial event was 11.2 (95% CI, 8.6-14.6). Adjusting for confounding had no substantive effect on this result.
  
  
  CONCLUSIONS
  The risk of an allergic-like event after penicillin is markedly increased in those who have had a prior event, although the absolute difference is small (1.72%). Represcription of penicillin to such patients is more frequent than anticipated.
authors.affiliation: Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Medicine, University of Pennsylvania, 3600 Spruce Street, Philadelphia, PA 19104, USA.
authors.forename: Andrea J
authors.initials: AJ
authors.lastname: Apter
authors.forename: Judith L
authors.initials: JL
authors.lastname: Kinman
authors.forename: Warren B
authors.initials: WB
authors.lastname: Bilker
authors.forename: Maximilian
authors.initials: M
authors.lastname: Herlim
authors.forename: David J
authors.initials: DJ
authors.lastname: Margolis
authors.forename: Ebbing
authors.initials: E
authors.lastname: Lautenbach
authors.forename: Sean
authors.initials: S
authors.lastname: Hennessy
authors.forename: Brian L
authors.initials: BL
authors.lastname: Strom
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004342:Drug Hypersensitivity / Q000209:etiology*; D011307:Drug Prescriptions / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D010406:Penicillins / Q000009:adverse effects*; D012008:Recurrence; D012189:Retrospective Studies; D012307:Risk Factors
chemical_list: D010406:Penicillins