Doxycycline Hyclate

DOXYCYCLINE HYCLATE- doxycycline hyclate tablet, film coated
PD-Rx Pharmaceuticals, Inc.

Rx only

DESCRIPTION

Doxycycline hyclate is available as a 20 mg tablet formulation of doxycycline for oral administration.

The structural formula of doxycycline hyclate is:

Chemical Structure
(click image for full-size original)

with an empirical formula of (C 22 H 24 N 2 O 8 •HCl) 2 •C 2 H 6 O•H 2 O and a molecular weight of 1025.89. The chemical designation for doxycycline is 4-(dimethylamino)-1, 4, 4a, 5, 5a, 6, 11, 12a-octahydro-3, 5, 10, 12, 12a-pentahydroxy-6-methyl-1,11-dioxo-2-naphthacenecarboxamide monohydrochloride, compound with ethyl alcohol (2:1), monohydrate.

Doxycycline hyclate is a yellow to light-yellow crystalline powder which is soluble in water.

Each tablet for oral administration contains 23 mg doxycycline hyclate equivalent to 20 mg of doxycycline. In addition, each tablet contains the following inactive ingredients: anhydrous lactose, carnauba wax, croscarmellose sodium, hypromellose, magnesium stearate, microcrystalline cellulose, polydextrose, polyethylene glycol, titanium dioxide, and triacetin.

CLINICAL PHARMACOLOGY

After oral administration, doxycycline hyclate is rapidly and nearly completely absorbed from the gastrointestinal tract. Doxycycline is eliminated with a half-life of approximately 18 hours by renal and fecal excretion of unchanged drug.

Mechanism of Action

Doxycycline has been shown to inhibit collagenase activity in vitro. 1 Additional studies have shown that doxycycline reduces the elevated collagenase activity in the gingival crevicular fluid of patients with adult periodontitis. 2,3 The clinical significance of these findings is not known.

Microbiology

Doxycycline is a member of the tetracycline class of antibiotics. The dosage of doxycycline achieved with this product during administration is well below the concentration required to inhibit microorganisms commonly associated with adult periodontitis. Clinical studies with this product demonstrated no effect on total anaerobic and facultative bacteria in plaque samples from patients administered this dose regimen for 9 to 18 months. This product should not be used for reducing the numbers of or eliminating those microorganisms associated with periodontitis.

Susceptibility Testing

For specific information regarding susceptibility test interpretive criteria and associated test methods and quality control standards recognized by FDA for this drug, please see: https://www.fda.gov/STIC.

Pharmacokinetics

The pharmacokinetics of doxycycline following oral administration of doxycycline hyclate were investigated in 4 volunteer studies involving 107 adults. Additionally, doxycycline pharmacokinetics have been characterized in numerous scientific publications. 4 Pharmacokinetic parameters for doxycycline hyclate following single oral doses and at steady-state in healthy subjects are presented as follows:

Pharmacokinetic Parameters for Doxycycline Hyclate Tablets
n Cmax *
(ng/mL)
Tmax
(hr)
CI/F *
(L/hr)
t 1/2 *
(hr)
*
Mean ± SD
Mean and range
Steady-State data were obtained from normal volunteers administered a bioequivalent formulation.

Single dose 20 mg
(tablet)

20

362 ± 101

1.4
(1.0–2.5)

3.85 ± 1.3

18.1 ± 4.85

Steady-State 20 mg
BID

30

790 ± 285

2
(0.98–12.0)

3.76 ± 1.06

Not
Determined

Absorption

Doxycycline is well absorbed after oral administration. In a single-dose study, concomitant administration of doxycycline hyclate with a 1000 calorie, high-fat, high-protein meal which included dairy products, in healthy volunteers, resulted in a decrease in the rate and extent of absorption and delay in the time to maximum concentrations.

Distribution

Doxycycline is greater than 90% bound to plasma proteins. Its apparent volume of distribution is variously reported as between 52.6 and 134 L. 4,6

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 variously reported that between 29% and 55.4% of an administered dose can be accounted for in the urine by 72 hours. 5,6 Half-life averaged 18 hours in subjects receiving a single 20 mg doxycycline dose.

Special Populations

Geriatric

Doxycycline pharmacokinetics have not been evaluated in geriatric patients.

Pediatric

Doxycycline pharmacokinetics have not been evaluated in pediatric patients (See WARNINGS section).

Gender

Doxycycline pharmacokinetics were compared in 9 men and 11 women under fed and fasted conditions. While female subjects had a higher rate (Cmax) and extent of absorption (AUC), these differences are thought to be due to differences in body weight/lean body mass. Differences in other pharmacokinetic parameters were not significant.

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