6 Extravascular routes of drug administration

122 Basic Pharmacokinetics
Table 6.2 Lincomycin, an antibiotic used when patient is allergic to penicillin or when penicillin is inappropriate
Route of administration Fraction absorbed Mean peak serum concentration (µg mL −1 ) Peak time (h)
Oral a 0.30 2.6 2 to 4
Intramuscular Not available 9.5 0.5
Intravenous 1.00 19.0 0.0
a Not commercially available in the USA.
Table 6.3 Haloperidol (Haldol), a drug used for psychotic disorder management
Route of administration Percentage absorbed Peak time (h) Half life (h [range])
Oral 60 2 to 6 24 (12–38)
Intramuscular 75 0.33 21 (13–36)
Intravenous 100 Immediate 14 (10–19)
Table 6.4 Ranitidine HCl (Zantac)
Route and dose Fraction absorbed Mean peak levels (ng mL −1 ) Peak time (h)
Oral (150 mg) 0.5–0.6 440–545 1–3
Intramuscular or intravenous (50 mg) 0.9–1.0 576 0.25
KaFX0 Ioral =
V (Ka – K )
C p (ng mL –1 )
I IV = (C p ) 0 = X 0 /V = highest concentration value
Oral route
Time (h)
IV route
Slope = –K
2.303
Figure 6.20 Administration of a drug by intravascular (IV) and extravascular (oral) routes (one-compartment model). Even for
administration of the same dose, the value of plasma concentration (Cp) at time zero [(Cp)0] for the intravenous bolus may be
higher than the intercept for the extravascular dose. This will be determined by the relative magnitudes of the elimination rate
constant (K ) and the absorption rate constant (Ka) and by the size of fraction absorbed (F) for the extravascular dosage form. X0,
oral dose of drug; X0, IV bolus dose of drug.
t 1/2 =
Sample chapter for Basic Pharmacokinetics 2nd edition
0.693
K