Comparison of Doxycycline 200 mg once daily for six weeks versus Doxycycline 200 mg once daily for two weeks + placebo for four weeks. Primary objective is to answer the question "is two weeks doxycycline treatment (currently suggested treatment) at least as effective as six weeks doxycycline treatment in Lyme Neuroborreliosis?".Key secondary objectives are to provide a better understanding of the pathogenesis and long-term complaints, and to search for new biomarkers in Lyme Neuroborreliosis (LNB) by collecting clinical data, blood, and cerebrospinal fluid (CSF) in a biobank for future research

Endpoints:

Primary endpoint: Improvement on a composite clinical score from inclusion to six months after ended treatment defined as clinical score at inclusion minus clinical score at six months.

Secondary endpoints: Improvement on a composite clinical score 12 months after ended treatment. Fatigue Severity Scale (FSS),Patient Health Questionnaire (PHQ-15), Short Form 36 (SF-36) and blood and CSF findings at inclusion, after 6 and 12 months.

The study design is a multicenter, non-inferiority, randomized, penta-blind, placebo-controlled trial. 120 patients will be included from approximately 8 Norwegian hospitals.

Main inclusion criteria are neurological symptoms suggestive of LNB without other obvious reasons, one or both of a) Cerebrospinal fluid pleocytosis (>5 leukocytes/mm3) b) intrathecal Bb antibody Production and signed informed consent. Safety assessments during the trial: Comparison of clinical outcome six months after end of treatment between the two treatment groups. Subjective experiences and blood tests including hematology and biochemistry for four weeks after ended treatment.

Inclusion Criteria:

1. Neurological symptoms suggestive of LNB without other obvious reasons and one or both of

   1. Cerebrospinal fluid pleocytosis ≥5 leukocytes pr mm3
   2. Intrathecal Bb antibody production

2. Signed informed consent

Exclusion Criteria:

• Age less than 18 years
• Pregnancy, breast-feeding
• Adverse reaction to tetracyclines
• Treatment with cephalosporin, penicillin, or tetracycline the last 14 days
• Serious liver or kidney disease that contraindicates use of doxycycline
• Lactose intolerance
• Need to use medications contraindicated according to Summary of Product Characteristics of the Investigational Medicinal Product

Follow-up period of 12 months. Patient diary filled out for 10 weeks after start of treatment. Blood sampling at 2 and 4 weeks after start of treatment.

Definition used from Good Clinical Practice. In addition registered patient reported symptoms of side effects.