Impact of oseltamivir use on complications in patients with influenza: a prospective study

Konstantinos Z. Vardakas, George Theocharis, Giannoula S. Tansarli, Spyridon Barbas, Theodoros Spyropoulos, Matthew E. Falagas

  1. Alfa Institute of Biomedical Sciences (AIBS), Athens, Greece
  2. SOS doctors, Athens, Greece
  3. Department of Internal Medicine - Infectious Diseases, Mitera Hospital, Athens, Greece
  4. Department of Medicine, Tufts University School of Medicine, Boston, Massachusetts, USA

ABSTRACT

Objective:

To evaluate the factors associated with oseltamivir prescription and the impact of oseltamivir use on the emergence of influenza complications.

Methods:

This prospective observational study evaluated patients who called the SOS Doctors in Attica, Greece, during the influenza epidemic between December 2011 and April 2012. Patients with a diagnosis of confirmed (using a direct test or PCR) or suspected (symptom-based) influenza according to the assessment of the attending physician were included in the study. All analyses were performed with SPSS 17.0 software.

Results:

410 patients with confirmed or suspected influenza were included. Patients were mainly females (63.7%); the median age of all patients was 44 years. The most commonly encountered co-morbidity was hypertension (17.8%), followed by endocrine diseases (13.2%) and obesity (12.7%). Vaccination rate was low; only 6.6% have been vaccinated before the current influenza season. The median duration of symptoms prior to the physicianʼs visit was 48h. The diagnosis of influenza was based on clinical criteria for the majority of patients (65.8%). Oseltamivir was prescribed in 45.4% of patients. Antibiotics were prescribed in 20.5% of all patients and in 17.2% of those who also received oseltamivir. In the multivariate analysis, following adjustment for age and co-morbidity, use of oseltamivir was associated with the attending physician (p<0.001), positive influenza test (p<0.001) and diabetes (p=0.027). Nasal congestion was negatively associated with oseltamivir use in the multivariate analysis (p<0.001). Out of the 351 patients who were available for assessment of outcome, 50 (15.8%) reported a complication at the follow-up phone-call, including bronchitis (7.4%), sinusitis (2.2%), pneumonia (2 %), pharyngitis (1.1%) and otitis (0.6%). Seven patients required hospitalization. In the multivariate analysis, following adjustment for age and co-morbidity, development of complications was associated with urinary tract disease (p=0.018), oseltamivir use (p<0.001), obesity (p=0.025), and prior vaccination at any time (p=0.005). The degree of oseltamivir use by the individual physicians (p=0.002) and use of ACEi (p=0.047) were associated with fewer complications.

Conclusion:

Prescription of oseltamivir depended on the attending physician and positive influenza tests. Use of oseltamivir was associated with more complications, but complications were less frequent among physicians who prescribed oseltamivir in the majority of their patients.