Inclusion Criteria:

• a) Healthy male and female subjects of at least 18 years of age. b) Informed of the nature of the study and given written informed consent. c) Have a body mass index between 18 and 30 and weighing at least 110 pounds. d) In good health as determined by lack of clinically significant abnormalities in health assessments performed at screening as judged by the physician.

Exclusion Criteria:

• a) Hypersensitivity to Doxycycline monohydrate (Adoxa®), or related compounds such as tetracycline.

  b) Any history of a clinical condition which might affect drug absorption, metabolism or passage out of the body, e.g. sprue, celiac disease, Crohn's disease, colitis, liver, kidney or thyroid conditions.

  c) Recent history of mental illness, drug addiction, drug abuse or alcoholism. d) Donation of greater than 500 ml of blood in the past 4 weeks prior to study dosing or difficulty in donating blood.

  e) Received an investigational drug within the 4 weeks prior to study dosing. f) Currently taking any systemic prescription medication, except for oral/ cutaneous/ vaginal hormone contraceptives, within the 7 days prior to study dosing or over-the-counter medication within 3 days of study dosing. This prohibition does not include vitamins or herbal preparations taken as nutritional supplements for non-therapeutic indications as judged by the attending physician. Any nonprescription medication consumption reported will be reviewed by the investigator prior to dosing. At the discretion of the investigator these volunteers may be enrolled if the medication is not anticipated to alter study integrity.

  g) Regular smoking of more than 5 cigarettes per week or the daily use of nicotine-containing products beginning 3 months before study medication administration through the final evaluation.

  h) If female, the subject is lactating or has a positive pregnancy test at screening and prior to each of the two treatment periods. Females of child bearing potential must use a 'medically acceptable method of contraception throughout the entire study period and for one week after the study is completed. Medically acceptable methods of contraception that may be used by the subject and/or her partner are: oral contraceptives/ patches, progestin injection/ implants, condom with spermacide, diaphragm with spermacide, IUD, vaginal spermicidal suppository, surgical Sterilization of themselves or their partner(s) or abstinence. Females taking oral Contraceptives must have taken them consistently for at least three months prior to receiving study medication.

  i) Alcohol, grapefruit beverages or foods or caffeine beverages or foods beginning 24 hours before each study medication administration through each study confinement period. Such restricted items include coffee, tea, iced tea, coke, Pepsi, Mountain Dew, chocolate, brownies, etc.

  j) Significant history or current evidence of chronic infectious disease, system disorders or organ dysfunction k) Regular use of any drugs known to induce or inhibit hepatic drug metabolism (e.g. barbiturates, carbamazepine, rifampin, phenylhydantaoins, phenothiazines, cimetidine, Omeprazole, macrolides, imidazoles, fluoroquinolines) within 30 days prior to study administration l) Positive test results for: HIV, Hepatitis B surface antigen, Hepatitis C antibody, drugs of abuse, or pregnancy at screening.