Active Ingredients: Doxycycline
The mechanisms responsible for decreased absorption appear to be chelation and an increase in gastric pH. Recent research has shown no significant loss of effectiveness in oral contraceptives while using most tetracycline antibiotics including doxycycline, although many physicians still recommend the use of barrier contraception for people taking the drug to prevent unwanted pregnancy.
Doxycycline crosses into breastmilk. The best available evidence indicates that doxycycline has little or no effect on hypoplasia of dental enamel or on staining of teeth and the CDC recommends the use of doxycycline for treatment of Q fever and also for tick-borne rickettsial diseases in young children and others advocate for its use in malaria.
It works by preventing bacteria from reproducing through the inhibition of protein synthesis. It can also be re-absorbed in the renal tubules and gastrointestinal tract due to its high lipophillicity so has a long elimination half life, and does not accumulate in the kidneys of patients with kidney failure due to the compensatory excretion in faeces.
It inhibits the synthesis of bacterial proteins by binding to the 30 S ribosomal subunit, which is only found in bacteria.
On examination, re-infection typically presents with an erythema migrans lesion at a different site than the original lesion more than 1-2.
Laboratory diagnosis of re-infection becomes a challenge, given that serology, including IgM, can remain positive for many years Note de bas de page 92.
Diagnosis is reliant on the clinical presentation of a new erythema migrans lesion at a different site.
Recent data suggest that patients treated for re-infection have excellent outcomes. Patients with re-infection reported less fatigue than both the non-infected control group and patients with their first infection, suggesting that repeated infections present a lower risk of persistent symptoms Note de bas de page 91.
Conclusions Lyme disease is an emerging infection in Canada, and it is important that clinicians be aware of its epidemiology, clinical presentations and management.
While sporadic cases of Lyme disease are possible from infected ticks that are imported on migrating birds, individuals living in or traveling to Lyme-endemic regions will be at greatest risk of infection.
A thorough travel history is essential in a person presenting with symptoms suggestive of Lyme disease, particularly if symptoms compatible with one of the neurologic syndromes that are more common in Europe are present. It is important to inform the laboratory of a positive travel history, as the serologic testing for North American and European Borrelia strains is different.
Given the constantly expanding tick population it can be challenging to clearly define regions constituting the highest risk for Lyme disease, and it is important to remain abreast of local Lyme epidemiology through local public health.
References Note de bas de page 1 Kuehn, BM.
How big is the Lyme problem?