Table 2. Characteristics of the monthly antimicrobial use time series, January 1996–December 2000.
| Antimicrobial drug class | Average monthly usea (minimum–maximum) | Trendb | Seasonalityc |
|---|---|---|---|
| Combinations of penicillins with β-lactamase inhibitors | 228.6 (119.9–334.9) | Upward | Yes (0.294) |
| β-lactamase resistant penicillins | 116.1 (49.1–202.1) | No | No |
| Macrolides | 90.2 (32.7–177.9) | Upward | Yes (0.371) |
| Penicillins with extended spectrum | 90.1 (43.9–177.4) | No | No |
| Third-generation cephalosporins | 62.5 (43.8–103.1) | Upward | Yes (0.226) |
| β-lactamase-sensitive penicillins | 54.6 (0–110.5) | No | No |
| Combinations of sulfonamides and trimethoprim, including derivatives | 52.9 (0–86.8) | No | No |
|---|---|---|---|
| Fluoroquinolones | 51.9 (19.4–87.5) | Upward | No |
| Second-generation cephalosporins | 32.9 (5.3–87.1) | Downward | No |
| Other antibacterial drugsd | 32.7 (16.3–45.9) | Upward | No |
| Tetracyclines | 30.9 (0–63.4) | Downward | No |
| Aminoglycosides | 24.8 (11.8–44.1) | Upward | Yes (0.236) |
| Glycopeptides | 13.5 (4.6–25.5) | Upward | No |
| Lincosamides | 6.1 (0–15.7) | Upward | Yes (0.208) |
| First-generation cephalosporins | 5.2 (0.7–14.5) | No | No |
| Carbapenems | 4.0 (0–8.5) | No | No |
aDefined daily doses (DDD) per 1,000 mean patient-days. bBased on regression of the series on time (according to the results of Dickey-Fuller unit root tests, none of the series needed to be differenced). cAutocorrelation of order 12, based on the correlogram and the partial correlogram. When seasonality was present, the figure in parenthesis indicates the estimated autocorrelation of order 12, i.e., the correlation between antimicrobial use on a given month and use on the same month 1 year before. dAmphenicols, monobactams, other quinolones, imidazoles, fusidic acid, and nitrofurantoin derivatives.