The pill imprinted with CY 186 is Doxycycline Hyclate 100 mg, a broad-spectrum antibiotic belonging to the tetracycline class.
Pill Identification
Attribute – Details
- Imprint – CY on the cap, 186 on the body
- Active Ingredient – Doxycycline Hyclate (100 mg)
- Color & Shape – Light blue, oblong/capsule
- Size – 22 mm
- Drug Class – Tetracycline class antibiotic
- Controlled Status – Prescription only; Non-controlled substance
Mechanism of Action
Doxycycline is primarily a bacteriostatic antibiotic. It inhibits bacterial protein synthesis through a specific mechanism:
- Ribosomal Binding: It reversibly binds to the 30S ribosomal subunit of susceptible microorganisms.
- Inhibition of Translation: This binding prevents transfer RNA (tRNA) from attaching to the ribosomal acceptor (A) site, halting the addition of amino acids to growing peptide chains.
- Broad Spectrum: It covers Gram-positive and Gram-negative bacteria, atypical pathogens (Mycoplasma, Chlamydia), spirochetes (Borrelia burgdorferi), and the erythrocytic forms of Plasmodium falciparum (malaria).
Common Indications & Typical Dosage
Dosing varies based on the underlying infection and clinical severity:
- General Bacterial Infections & Acne: Usually 100 mg every 12 hours (or 200 mg on day 1 followed by 100 mg once or twice daily).
- Lyme Disease (Early Stage): 100 mg orally twice daily for 10–21 days.
- Malaria Prophylaxis: 100 mg once daily, initiated 1–2 days prior to entering an endemic zone, continued daily throughout the stay, and maintained for 4 consecutive weeks after departure.
- Administration Instructions: Take each dose with a full glass of water (8 oz / 240 mL) and remain upright for at least 30 minutes to prevent esophageal irritation.
Side Effects
- Gastrointestinal: Nausea, vomiting, epigastric distress, diarrhea, and appetite loss.
- Dermatologic: Marked photosensitivity; standard sunlight exposure can cause severe sunburn, rash, or erythema.
- Secondary Infections: Vaginal candidiasis (yeast infection) or oral thrush due to disruption of normal microflora.
- Severe / Rare Effects: Clostridioides difficile-associated colitis, severe skin reactions (DRESS, Stevens-Johnson syndrome), and hypersensitivity reactions.
Key Precautions & Drug Interactions
- Chelation & Cation Binding: Doxycycline binds tightly with multivalent ions. Avoid taking it within 2 to 3 hours of calcium-rich dairy, antacids (aluminum/magnesium), iron supplements, bismuth subsalicylate, or zinc products, as they substantially decrease absorption.
- Drug Interactions: May reduce the efficacy of oral contraceptives and bacteriocidal antibiotics (like penicillins); may enhance the anticoagulant effect of warfarin.
- Hepatic Monitoring: Use with caution in patients with hepatic impairment or those taking concurrent hepatotoxic medications.
Critical Warnings
- Tooth Discoloration & Bone Growth: Contraindicated during tooth development (pregnancy, nursing, and children under 8 years of age), as it causes permanent yellow-gray-brown discoloration of teeth and reversible suppression of skeletal growth.
- Pill-Induced Esophagitis: Capsules lodging in the esophagus can cause deep mucosal ulceration. Never take this medication immediately before lying down.
- Intracranial Hypertension (Pseudotumor Cerebri): Can cause elevated cerebrospinal fluid pressure; symptoms include persistent headache, dizziness, and blurred or double vision.
- Toxicity of Expired Medication: Outdated or degraded tetracyclines can cause severe renal tubular dysfunction (Fanconi syndrome); discard expired medication immediately.