<p><strong>Anticoagulants</strong>: Plasma prothrombin activity is depressed by tetracyclines. Reduced doses of any concomitant anticoagulants may be necessary.<br />
<strong>ACE inhibitors, antacids and adsorbants</strong>: Tetracyclines bind to di-/tri-valent cations. Absorption from the gastrointestinal tract is impaired by the concomitant administration of iron, calcium, aluminium, magnesium, bismuth and zinc salt (interactions with specified salts, antacids, kaolin, bismuth containing ulcer-healing drugs, quinapril which contains a magnesium carbonate excipient). Dosages should be maximally separated. Absorption of tetracyclines is not significantly impaired by food, milk and milk products.<br />
<strong>Diuretics</strong>: Diuretics may aggravate nephrotoxicity by volume depletion.<br />
<strong>Antibacterials</strong>: Minocycline should not be used with penicillins.<br />
<strong>Ergotamine and ergometrine</strong>: There is an increased risk of ergotism.<br />
Oral contraceptives: Both can induce hyperpigmentation.<br />
<strong>Retinoids</strong>: Administration of isotretinoin should be avoided shortly before, during and shortly after minocycline therapy.</p>