Case Study – Doxycycline

Case Presentation: AP is a 67-year-old woman
Medical Conditions: depression, gout, and hypercholesterolemia.
New Rx: doxycycline for the treatment of cellulitis.

AP is concerned about stomach problems, as most oral medications cause her to experience bloating and diarrhea. She remembers that the pharmacist recently told her she can take 1 of her medications with food or milk to help minimize stomach issues. AP wants to know if she can take her new prescription for doxycycline with milk. How should the pharmacist respond?

Answer:

Counsel AP to take her doxycycline on an empty stomach 1 hour before or 2 hours after meals. The calcium in dairy products, such as milk, can interfere with the absorption of doxycycline. Calcium ions can bind to doxycycline and form a chelate, thus reducing its absorption. This may also reduce the effectiveness of AP's cellulitis treatment.1 To be safe, she will need to change how she takes her medications for the duration of her doxycycline therapy.

Clinical Tips
Doxycycline
  • A broad-spectrum tetracycline antibiotic drug, deoxytetracycline, that is well absorbed when taken by mouth, even after food.
  • Indications: treatment of Infectious diseases such as:  rickettsiosis–eg, Rocky mountain spotted fever, typhus fever, Q fever, rickettsialpox, tick fevers, RTIs from Mycoplasma pneumoniae, lymphogranuloma venereum, trachoma, inclusion conjunctivitis, etc, due to Chlamydia trachomatis, psittacosis–C psittaci, nongonococcal urethritis–Ureaplasma urealyticum, relapsing fever–Borrelia recurrentis, gram-negative microorganisms: Chancroid–Haemophilus ducreyi, plague–Yersinia pestis, tularemia–Francisella tularensis, cholera–Vibrio cholerae, Campylobacter fetus, Brucella spp, Bartonella bacilliformis, Calymmatobacterium granulomatis, malaria prophylaxis–Plasmodium falciparum in travelers to chloroquine and/or pyrimethamine-sulfadoxine resistant areas
  • Adverse effects: GI tract disturbances, anorexia, N&V, diarrhea, glossitis, dysphagia, enterocolitis, anogenital Candida overgrowth, photophobia.

  • Precautions: Use cautiously in: renal disease, hepatic impairment, nephrogenic diabetes insipidus, cachexia, pregnant or breastfeeding patients, children younger than age 8.

Cellulitis

  • Cellulitis is a spreading bacterial infection just below the skin surface. It is most commonly caused by Streptococcus pyogenes or Staphylococcus aureus.
  • Treatment: Antibiotic treatment is the only way to battle this potentially life-threatening infection. Mild to moderate cellulitis can be treated with the following antibiotics taken every four to eight hours by mouth: penicillins (Bicillin, Wycillin, Pen Vee, V-Cillin), erythromycin (E-Mycin, Ery-Tab), cephalexin (Biocef, Keflex), cloxacillin (Tegopen), and Tetracyclines.
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