ORACEA capsules are not bioequivalent to other doxycycline products. The
pharmacokinetics of doxycycline following oral administration of ORACEA was
investigated in 2 volunteer studies involving 61 adults. Pharmacokinetic
parameters for ORACEA following single oral doses and at steady-state in healthy
subjects are presented in Table 1.
Table 1. Pharmacokinetic Parameters [Mean (± SD)] for ORACEA
| N
| Cmax * (ng/mL) | Tmax ** (hr) | AUC0-∞ * (ng∙hr/mL) | t1/2 (hr) *
|
Single Dose 40 mg capsules | 30
| 510 ± 220.7 | 3.00 (1.0-4.1)
| 9227 ± 3212.8 | 21.2 ± 7.6 |
Steady-State *** 40 mg capsules
| 31
| 600 ± 194.2 | 2.00 (1.0-4.0)
| 7543 ± 2443.9 | 23.2 ± 6.2 |
* Mean
** Median
*** Day 7
Absorption
In a single-dose food-effect study involving administration of
ORACEA to healthy volunteers, concomitant administration with a 1000 calorie,
high-fat, high-protein meal that included dairy products, resulted in a decrease
in the rate and extent of absorption (Cmax and AUC) by about 45% and 22%,
respectively, compared to dosing under fasted conditions. This decrease in
systemic exposure can be clinically significant, and therefore if ORACEA is
taken close to meal times, it is recommended that it be taken at least one hour
prior to or two hours after meals.
Distribution
Doxycycline is greater than 90% bound to plasma proteins.
Metabolism
Major metabolites of doxycycline have not been identified.
However, enzyme inducers such as barbiturates, carbamazepine, and phenytoin
decrease the half-life of doxycycline.
Excretion
Doxycycline is excreted in the urine and feces as unchanged drug.
It is reported that between 29% and 55.4% of an administered dose can be
accounted for in the urine by 72 hours. Terminal half-life averaged 21.2 hours
in subjects receiving a single dose of ORACEA.
Special PopulationsGeriatric
Doxycycline pharmacokinetics have not been evaluated in geriatric
patients.
Pediatric
Doxycycline pharmacokinetics have not been evaluated in pediatric
patients (see WARNINGS
section).
Gender
The pharmacokinetics of ORACEA were compared in 16 male and 14
female subjects under fed and fasted conditions. While female subjects had a
higher Cmax and AUC than male subjects, these differences were thought to be due
to differences in body weight/lean body mass.
Race
Differences in doxycycline pharmacokinetics among racial groups
have not been evaluated.
Renal Insufficiency
Studies have shown no significant difference in serum half-life
of doxycycline in patients with normal and severely impaired renal function.
Hemodialysis does not alter the serum half-life of doxycycline.
Hepatic Insufficiency
Doxycycline pharmacokinetics have not been evaluated in patients
with hepatic insufficiency.
Gastric Insufficiency
In a study in healthy volunteers (N=24) the bioavailability of
doxycycline is reported to be reduced at high pH. This reduced bioavailability
may be clinically significant in patients with gastrectomy, gastric bypass
surgery or who are otherwise deemed achlorhydric.
Drug Interactions
(see PRECAUTIONS section)