title: Prevalence, risk factors and main features of adverse drug reactions leading to hospital admission.
abstract: OBJECTIVE
  To assess the prevalence of hospital admission related to adverse drug reactions (ADRs) in a third-level hospital, to analyse the associated factors, and to describe the reactions and the drugs involved.
  
  
  METHODS
  A cross-sectional study was conducted for a 120-day period. Patients that were urgently hospitalized entered the study. The primary endpoint was the ADR-related urgent admission. A descriptive analysis of demographic, clinical, and drug-related variables was performed. The association between the likelihood of urgent admission due to ADRs and age, gender, and number of drugs used was analysed. A descriptive analysis of the suspected drugs and the reactions in ADR-related admissions was performed.
  
  
  RESULTS
  Overall, 186 out of 4,403 hospital admissions were due to ADRs (prevalence: 4.2 % [95 % CI 3.7-4.8 %]). Age (≥65 years: OR 1.59 [95 % CI 1.10-2.29]) and number of drugs used at the time of admission (3-5 drugs: OR 5.07 [95 % CI 2.71-9.59]; 6-9 drugs: OR 5.90 [95 % CI 3.16-11.0]; ≥10 drugs: OR 8.94 [95 % CI 4.73-16.89]), but not gender, were identified as independent factors associated with ADR-related hospitalization. The overall in-hospital stay for patients admitted with ADRs amounted to 1,785 days. The ADRs were mainly type A reactions (92 %). Acute renal failure related to renin-angiotensin system inhibitors, haemorrhage due to anticoagulants, and upper gastrointestinal bleeding related to antiplatelet drugs and/or non-steroidal anti-inflammatory drugs were the most frequent.
  
  
  CONCLUSIONS
  Over 4 % of urgent hospitalizations are caused by ADRs, which are dose-related and predictable in more than 90 % of cases. The main risk factors are advanced age and polypharmacy.
authors.affiliation: Clinical Pharmacology Service, Bellvitge University Hospital, c/Feixa Llarga s/n, 08907 L'Hospitalet de Llobregat, Barcelona, Spain, cpedros@bellvitgehospital.cat.
authors.forename: Consuelo
authors.initials: C
authors.lastname: Pedrós
authors.forename: Beatriz
authors.initials: B
authors.lastname: Quintana
authors.forename: Mireia
authors.initials: M
authors.lastname: Rebolledo
authors.forename: Núria
authors.initials: N
authors.lastname: Porta
authors.forename: Antoni
authors.initials: A
authors.lastname: Vallano
authors.forename: Josep Maria
authors.initials: JM
authors.lastname: Arnau
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D064420:Drug-Related Side Effects and Adverse Reactions / Q000453:epidemiology*; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D019338:Polypharmacy; D015995:Prevalence; D012307:Risk Factors; D055815:Young Adult