LymePak (Page 3 of 5)

12.4 Microbiology

Mechanism of Action

Doxycycline inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit. Doxycycline has bacteriostatic activity against a broad range of gram-positive and gram-negative bacteria.


Cross resistance with other tetracyclines is common.

Antimicrobial Activity

Culture and susceptibility testing are not routinely performed to establish the diagnosis of early Lyme disease; standard methods for susceptibility testing of Borrelia burgdorferi have not been established. The in vitro susceptibility of Borrelia burgdorferi to doxycycline has been reported in the literature; however, the clinical significance of these findings is unknown.


13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Long-term studies in animals to evaluate carcinogenic potential of doxycycline have not been conducted. However, there has been evidence of oncogenic activity in rats in studies with the related antibacterial drugs, oxytetracycline (adrenal and pituitary tumors), and minocycline (thyroid tumors).

Likewise, although mutagenicity studies of doxycycline have not been conducted, positive results using in vitro mammalian cell assays have been reported for related antibacterial drugs (tetracycline, oxytetracycline).

Doxycycline administered orally at dosage levels as high as 250 mg/kg/day had no apparent effect on the fertility of female rats. Effect on male fertility has not been studied.

13.2 Animal Toxicology and/or Pharmacology

Hyperpigmentation of the thyroid has been produced by members of the tetracycline class in the following species: in rats by oxytetracycline, doxycycline, tetracycline PO 4 , and methacycline; in minipigs by doxycycline, minocycline, tetracycline PO 4 , and methacycline; in dogs by doxycycline and minocycline; in monkeys by minocycline.

Minocycline, tetracycline PO 4 , methacycline, doxycycline, tetracycline base, oxytetracycline HCl, and tetracycline HCl were goitrogenic in rats fed a low iodine diet. This goitrogenic effect was accompanied by high radioactive iodine uptake. Administration of minocycline also produced a large goiter with high radioiodine uptake in rats fed a relatively high iodine diet.

Treatment of various animal species with this class of drugs has also resulted in the induction of thyroid hyperplasia in the following: in rats and dogs (minocycline); in chickens (chlortetracycline); and in rats and mice (oxytetracycline). Adrenal gland hyperplasia has been observed in goats and rats treated with oxytetracycline.


14.1 Clinical Trial Experience

Doxycycline has been used in clinical practice for early stages of Lyme disease for several decades. Thorough search of the published literature identified 31 studies in which doxycycline treatment was used for the treatment of Lyme disease. Of these 31, three randomized studies evaluating doxycycline treatment in patients with erythema migrans and associated symptoms were identified 1-3. In addition, two natural history studies of Lyme disease evaluated disease progression in patients presenting with erythema migrans and associated symptoms 4,5. Over 200 patients from Lyme-disease hyperendemic areas were enrolled in these five studies, and more than 100 received doxycycline. Evidence of efficacy was derived by comparing the doxycycline treatment in studies using doxycycline 100 mg twice daily for 20-21 days with no treatment in the natural history studies. Clinical resolution of symptoms was defined as absence of objective late manifestations of Lyme disease, specifically those related to the musculoskeletal, nervous, and cardiac systems at 6 months. In comparison to untreated patients, doxycycline-treated patients had a higher response rate at 6 months. Doxycycline-treated patients had a response rate of 75-95% compared to 56-66% in untreated patients.


  1. Dattwyler RJ, Volkman DJ, Conaty SM, Platkin SP, Luft BJ. Amoxycillin plus probenecid versus doxycycline for treatment of erythema migrans borreliosis. Lancet 1990; 336(8728):1404-1406.
  2. Massarotti EM, Luger SW, Rahn DW, Messner RP, Wong JB, Johnson RC et al. Treatment of early Lyme disease. Am J Med 1992; 92(4):396-403.
  3. Dattwyler RJ, Luft BJ, Kunkel MJ, Finkel MF, Wormser GP, Rush TJ et al. Ceftriaxone compared with doxycycline for the treatment of acute disseminated Lyme disease. N Engl J Med 1997; 337(5):289-294.
  4. Steere AC, Hardin JA, Ruddy S, Mummaw JG, Malawista SE. Lyme arthritis: correlation of serum and cryoglobulin IgM with activity, and serum IgG with remission. Arthritis Rheum 1979b; 22(5):471-483.
  5. Steere AC, Malawista SE, Newman JH, Spieler PN, Bartenhagen NH. Antibiotic therapy in Lyme disease. Ann Intern Med 1980; 93(1):1-8.


LYMEPAK tablets contain 100 mg of doxycycline (equivalent to 115 mg doxycycline hyclate). The tablets are green, round, film-coated tablets engraved with LP-1 on one side.

NDC # 72135-596-86: is supplied as a child-resistant blister card containing 14 tablets
NDC # 72135-596-87: Unit of use carton containing 3 blister cards, total 42 tablets

Store at 20°C to 25°C (68°F to 77°F) excursions permitted to 15°C to 30°C (59°F to 86°F) [See USP Controlled Room Temperature]. Protect from light and moisture.


Advise the patient to read the FDA-approved patient labeling (Patient Information).

Important Administration and Safety Information for Patients and Caregivers

Advise all patients taking LYMEPAK:

  • to avoid excessive sunlight or artificial ultraviolet light while receiving LYMEPAK and to discontinue therapy if phototoxicity (e.g., skin eruption, etc.) occurs. Sunscreen or sunblock should be considered [see Warnings and Precautions (5.4)] .
  • to drink fluids liberally along with LYMEPAK to reduce the risk of esophageal irritation and ulceration [see Adverse Reactions (6)] .
  • that the absorption of tetracyclines is reduced when taken with foods, especially those which contain calcium. However, the absorption of LYMEPAK is not markedly influenced by simultaneous ingestion of food or milk [see Dosage and Administration (2.2)] .
  • that the absorption of tetracyclines is reduced when taken with antacids containing aluminum, calcium or magnesium, bismuth subsalicylate, and iron-containing preparations [see Drug Interactions (7.3)] .
  • that the use of LYMEPAK might increase the incidence of vaginal candidiasis [see Warnings and Precautions (5.10)] .
  • that LYMEPAK can make birth control pills less effective [see Drug Interactions (7.3)] .

Tooth Discoloration and Inhibition of Bone Growth

Advise patients that LYMEPAK, like other tetracycline-class drugs, may cause permanent tooth discoloration of deciduous teeth and reversible inhibition of bone growth when administered during the second and third trimesters of pregnancy. Tell your healthcare provider right away if you become pregnant during treatment [see Warnings and Precautions (5.1, 5.2) and Use in Specific Populations (8.1, 8.4)].


Advise women not to breastfeed during treatment with LYMEPAK and for 5 days after the last dose [see Use in Specific Populations (8.2)].

Jarisch-Herxheimer Reaction

Inform patients that a systemic reaction known as the Jarisch–Herxheimer reaction (JHR) may occur within 24 hours of starting LYMEPAK. Symptoms include shaking chills, fever, and intensification of skin rash and usually resolve within several hours. Advise patients to contact their health care provider if symptoms occur [see Warnings and Precautions 5.6] .

Development of Resistance

Patients should be counseled that antibacterial drugs, including LYMEPAK should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). When LYMEPAK is prescribed to treat a bacterial infection, patients should be told that although it is common to feel better early in the course of therapy, the medication should be taken exactly as directed. Skipping doses or not completing the full course of therapy may (1) decrease the effectiveness of the immediate treatment and (2) increase the likelihood that bacteria will develop resistance and will not be treatable by LYMEPAK or other antibacterial drugs in the future [see Warnings and Precautions 5.9] .


Diarrhea is a common problem caused by antibacterial drugs, including LYMEPAK, which usually ends when the antibacterials are discontinued. Sometimes after starting treatment with antibacterial drugs, patients can develop watery and bloody stools (with or without stomach cramps and fever) even as late as two or more months after having taken the last dose of the antibacterial drug. If this occurs, advise patients to contact their physician as soon as possible [see Warnings and Precautions 5.3] .

All resources are included in as near-original form as possible, meaning that the information from the original provider has been rendered here with only typographical or stylistic modifications and not with any substantive alterations of content, meaning or intent.

This site is provided for educational and informational purposes only, in accordance with our Terms of Use, and is not intended as a substitute for the advice of a medical doctor, nurse, nurse practitioner or other qualified health professional.

Privacy Policy | Copyright © 2021. All Rights Reserved.