Doxycycline

What it is

Doxycycline is a tetracycline antibiotic. It binds the bacterial ribosome and stops protein synthesis, halting bacterial growth. It is used for bacterial infections and, over longer courses, for inflammatory skin conditions such as acne.

A usual adult range, not a national label — the dose and the timing differ by country and by product.

Used for

• Bacterial infection
• Skin

Approved uses differ by country — some of these may be off-label or unapproved where you live.

What to know while taking it

It is taken with food to ease stomach upset, but away from dairy, since calcium, iron, magnesium and zinc bind it in the gut and reduce how much is absorbed; probiotics are likewise spaced apart. Each dose goes down with a full glass of water and an upright position afterwards, because the capsule can irritate or ulcerate the oesophagus if it lodges there. Sunlight sensitivity is common and marked, so strong sun and sunbeds are avoided during the course. It can increase the effect of the anticoagulant warfarin, and the course is finished in full even after symptoms fade.

When to see a doctor

Pain on swallowing, a burning sensation behind the breastbone, or the feeling that something is stuck warrants seeing a doctor rather than continuing. So does a severe or blistering sunburn-like rash, or unusual bruising or bleeding while also on warfarin.

Worth knowing

• Avoid strong sun
• Separate from dairy
• Take with a full glass of water, stay upright
• Finish the full course

Nutrients affected

• calcium — absorption blocked with (Calcium, ionized, Calcium, total, Ferritin)
• iron — absorption blocked with (Ferritin, Hematocrit, Hemoglobin)
• magnesium — absorption blocked with (Glucose, HOMA-IR, Magnesium)
• zinc — absorption blocked with (Free T3, Testosterone, TSH)