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Oral-Antral Fistula
First Line
Second Line
​​​Allergy status
(Confirm allergy status prior to choosing antimicrobial regime)
No penicillin allergy
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Check for interactions
 500mg every 8 hours
 200mg stat, then 100mg every 12 hours
 5 days


Doxycycline is ineffective if given with multi-valent cation containing products e.g. antacids, supplements or feeds containing calcium, iron, magnesium, zinc, sucralfate or bismuth. These products bind to doxycycline and reduce its absorption by over 90%.


If patients are prescribed antacids or supplements containing calcium iron, magnesium zinc or bismuth. It is advised these medications are stopped/withheld for the duration of antibiotic treatment. If this is not possible due to a clinical need, then an alternative antibiotic must be considered.
If doxycycline and a cation containing product must be prescribed together:
·         Administration times should be as far apart as possible
·         Reduce the dosing frequency of the interacting product if possible
·         In the case of oral nutritional supplements, multiple sips throughout the day should be replaced with set administration times to enable adequate spacing from oral antibiotic administration
·         If a patient is receiving an enteral feed doxycycline should generally be avoided unless there is a specific feed free window