When evaluating interactions involving tetracycline-class antibiotics, it is essential to focus on the specific medicine prescribed. The authoritative British National Formulary for Children (BNFC) published by the National Institute for Health and Care Excellence (NICE) maintains interaction entries specifically for oxytetracycline, rather than generalising across every tetracycline-class medicine.
Furthermore, the interactions listed by the source generally apply to systemic use and do not apply to topical oxytetracycline unless specifically stated. They also do not index combination formulations directly; patients and clinicians must check interactions for each active constituent medicine individually.
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Interactions Affecting Oral Absorption
For oral oxytetracycline, the source reports the following absorption or exposure effects and manufacturer timing advice:
- Oral Antacids: Greatly decrease the absorption of oral oxytetracycline. The manufacturer advises separating administration of oral antacids and oxytetracycline by 2 to 3 hours.
- Oral Iron: Decreases oral oxytetracycline absorption. The manufacturer advises taking oxytetracycline 2 to 3 hours after taking iron supplements.
- Oral Magnesium: Decreases absorption of oral oxytetracycline. The manufacturer advises separating doses by at least 2 to 3 hours.
- Dairy Products: Food and lifestyle guidance in the source specifies that dairy products decrease exposure to oxytetracycline.
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Severe Warnings and Specific Medication Interactions
Beyond absorption chelation in the gut, systemic oxytetracycline presents specific risks when co-administered with particular prescription medications:
#### Systemic Retinoids Concomitant administration of oxytetracycline with specific retinoids—namely acitretin, alitretinoin, isotretinoin, and tretinoin—increases the risk of benign intracranial hypertension (pseudotumor cerebri). In addition, hepatotoxicity risks are noted for these combinations (as well as vitamin A). The manufacturer explicitly advises avoiding combining oxytetracycline with these listed retinoids.
#### Anticoagulants (Warfarin) Oxytetracycline increases the anticoagulant effect of warfarin. The manufacturer advises regular monitoring of the International Normalised Ratio (INR). Any management or therapy changes must only occur under clinical supervision.
#### Lithium Oxytetracycline is predicted to increase the risk of lithium toxicity (lithium carbonate or lithium citrate). The manufacturer advises avoiding the combination or adjusting the lithium dose, which requires prescriber or pharmacist management rather than self-adjustment.
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Evidentiary Context
The BNFC oxytetracycline interaction listings incorporate varying descriptions of evidence across different entries—including study-based data, anecdotal reports, theoretical interactions, and predicted pharmacology. Consequently, not every listed entry shares identical evidentiary strength. Consult a doctor or pharmacist for a comprehensive evaluation of any prescribed regimen.