title: Co-possession of phosphodiesterase type-5 inhibitors (PDE5-I) with nitrates.
abstract: OBJECTIVE
  Estimate the proportion of phosphodiesterase type-5 inhibitor (PDE5-I) patients who co-possess nitrates and compare the proportion of tadalafil patients dispensed nitrates to a matched control group. Secondarily, examine the percentage of co-possession of PDE5-Is and nitrates where the products were dispensed on the same day or written by the same prescriber.
  
  
  METHODS
  Male patients aged 18+ years filling PDE5-I prescriptions between December 2003 and March 2006 were identified using a U.S. longitudinal prescription database (IMS Health LRx). Similar patients not dispensed a PDE5-I during this period were matched to the tadalafil-dispensed cohort using a propensity score approach. Co-possession, as a proxy for concurrent use, was defined as an overlap in time on therapy for a PDE5-I and nitrate and was compared for the three PDE5-Is and for tadalafil to the matched control group.
  
  
  RESULTS
  Among 601,063 tadalafil patients, 3.31% were dispensed a nitrate during the study period, compared to 6.18% in control patients (n = 601,063). When co-possessed prescriptions were defined by overlapping exposure periods, the proportion of PDE5-I patients with co-possessed nitrates ranged from 1.44% (tadalafil) to 1.72% (vardenafil) and 2.13% (sildenafil). Co-possession percentages of PDE5-I prescriptions were 0.83% for tadalafil and 1.07% for sildenafil and vardenafil. The majority (54.29%) of co-possessed PDE5-I and nitrate prescriptions had the nitrate dispensed prior to the PDE5-I prescription identified in the study cohort.
  
  
  CONCLUSIONS
  Keeping in mind the limitations of observational studies, these results suggest that co-dispensing of nitrates and PDE5-Is is low. Compared to control patients, the proportion of nitrate co-possession was lowest for patients filling tadalafil. Tadalafil patients also had the lowest co-possessed proportion among the three PDE5-I cohorts. While the majority of co-possessed drug pairs were prescribed by different providers, the highest percentage of co-prescribing from the same physician was among cardiologists. These results suggest that physicians adhere to contraindications and are careful about co-prescribing of nitrates with PDE-5Is.
authors.affiliation: IMS Health, Inc, Plymouth Meeting, PA 19422, USA.
authors.forename: Li-Ling
authors.initials: LL
authors.lastname: Chang
authors.forename: Mark
authors.initials: M
authors.lastname: Ma
authors.forename: Heather von
authors.initials: Hv
authors.lastname: Allmen
authors.forename: Scott C
authors.initials: SC
authors.lastname: Henderson
authors.forename: Kristine
authors.initials: K
authors.lastname: Harper
authors.forename: Kenneth
authors.initials: K
authors.lastname: Hornbuckle
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002243:Carbolines / Q000627:therapeutic use*; D016208:Databases, Factual; D004359:Drug Therapy, Combination; D007172:Erectile Dysfunction / Q000188:drug therapy; D006801:Humans; D007093:Imidazoles / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009566:Nitrates / Q000627:therapeutic use*; D010593:Pharmaceutical Services; D010726:Phosphodiesterase Inhibitors / Q000627:therapeutic use*; D010879:Piperazines / Q000627:therapeutic use*; D010818:Practice Patterns, Physicians'; D011687:Purines / Q000627:therapeutic use; D000068677:Sildenafil Citrate; D013450:Sulfones / Q000627:therapeutic use*; D000068581:Tadalafil; D014227:Triazines / Q000627:therapeutic use; D000069058:Vardenafil Dihydrochloride; D055815:Young Adult
chemical_list: D002243:Carbolines; D007093:Imidazoles; D009566:Nitrates; D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D014227:Triazines; D000069058:Vardenafil Dihydrochloride; D000068581:Tadalafil; D000068677:Sildenafil Citrate