The capsule debossed/imprinted with A45 (or A 45) is an oral prescription antibiotic containing Amoxicillin Trihydrate (500 mg).
- (Note: Other formulations bearing “a 45” include delayed-release Trilipix/fenofibric acid 45 mg capsules [brown/yellow] and Rinvoq 45 mg tablets [yellow]. However, the classic two-piece hard gelatin capsule imprinted “A45” is the generic 500 mg amoxicillin capsule).
Pill Identification
Attribute – Specification
- Active Ingredient – Amoxicillin (as Amoxicillin Trihydrate, USP) 500 mg
- Imprint – A45 (or A 45) in black ink on the capsule body
- Color & Shape – Blue cap / Pink body, hard gelatin capsule
- Size – Size 0 hard gelatin capsule (approximately 21 mm)
- Primary Manufacturers / Labelers – Aurobindo Pharma Limited / Rising Pharmaceuticals
- Drug Class – Aminopenicillin lactam antibacterial agent
- Controlled Substance Schedule – Non-controlled prescription (Rx-only)
Mechanism of Action
Amoxicillin is a semi-synthetic aminopenicillin with bactericidal activity against susceptible Gram-positive and select Gram-negative organisms:
- Inhibition of Cell Wall Synthesis: Amoxicillin diffuses across bacterial outer membranes and binds to specific penicillin-binding proteins (PBPs), primarily PBP-1A, -1B, -2, and -3, located on the inner surface of the bacterial cell wall.
- Blockade of Peptidoglycan Cross-Linking: Binding inhibits the transpeptidase and carboxypeptidase enzymes responsible for cross-linking peptidoglycan polymers, preventing the structural integrity of the cell wall from forming.
- Osmotic Lysis & Cell Death: The weakened bacterial cell wall triggers the activation of bacterial autolytic enzymes (autolysins and murein hydrolases), resulting in cell lysis, swelling, and bacterial cell death.
Indications and Clinical Uses
- Ear, Nose, and Throat (ENT) Infections: Acute otitis media, pharyngitis, tonsillitis, and acute bacterial rhinosinusitis.
- Lower Respiratory Tract Infections: Community-acquired pneumonia (CAP) and acute exacerbations of chronic bronchitis.
- Genitourinary Tract Infections: Acute uncomplicated cystitis and urethritis caused by susceptible E. coli or Enterococcus faecalis.
- Skin and Skin Structure Infections: Uncomplicated cellulitis and abscesses caused by non lactamase-producing streptococci and staphylococci.
- Helicobacter pylori Eradication: Part of dual or triple-therapy combination regimens (with a proton pump inhibitor and clarithromycin) for peptic ulcer disease.
Dosage and Administration
- Administer at evenly spaced intervals. Amoxicillin can be taken with or without meals, as food does not significantly impair oral bioavailability.
- Adults and Adolescents (> 40 kg):
- Mild to Moderate Infections: 500 mg orally every 12 hours or 250 mg every 8 hours.
- Severe Infections / Lower Respiratory Tract Infections: 875 mg every 12 hours or 500 mg every 8 hours for 7 to 14 days depending on infection severity.
- H. pylori Eradication: 1,000 mg (two 500 mg capsules) twice daily for 14 days in combination with standard anti-secretory/antibacterial therapy.
- Renal Impairment Dosing:
- 250 mg to 500 mg orally every 12 hours.
- 250 mg to 500 mg orally every 24 hours.
- Hemodialysis: 250 mg to 500 mg every 24 hours, with an additional dose administered post-dialysis.
Side Effects
Common Adverse Reactions:
- Gastrointestinal: Diarrhea, loose stools, nausea, vomiting, epigastric discomfort, candidiasis (oral thrush or vaginal yeast infection)
- Dermatologic: Non-allergic maculopapular “amoxicillin rash” (especially common in patients with Epstein-Barr virus / infectious mononucleosis)
- Central Nervous System: Mild headache, dizziness
Serious Adverse Reactions:
- Severe Anaphylaxis / Type I Hypersensitivity: Bronchospasm, laryngeal edema, urticaria, hypotension, and cardiovascular collapse.
- Severe Cutaneous Adverse Reactions (SCAR): Stevens-Johnson syndrome (SJS), Toxic Epidermal Necrolysis (TEN), and Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS).
- Clostridioides difficile-Associated Diarrhea (CDAD): Severe pseudomembranous colitis presenting with watery/bloody diarrhea, severe abdominal cramping, and fever.
- Hepatic Dysfunction: Cholestatic jaundice and elevated serum transaminases.
- Neurotoxicity / Seizures: Can occur in patients receiving high doses or those with unadjusted renal impairment.
Warnings and Precautions
- Hypersensitivity & Cross-Reactivity: Serious and occasionally fatal anaphylactic reactions have been reported in patients on penicillin therapy. Prior to initiation, confirm history of allergy to penicillins, cephalosporins, or other allergens. Cross-reactivity between penicillins and cephalosporins occurs in approximately 1% to 3% of patients.
- Infectious Mononucleosis: Avoid administering amoxicillin to patients with suspected or confirmed infectious mononucleosis, as a high percentage develop a widespread, non-allergic erythematous maculopapular rash.
- Clostridioides difficile Colitis: If persistent, severe diarrhea occurs during or weeks after treatment, evaluate immediately for C. difficile and avoid anti-motility agents.
- Superinfections: Prolonged use may promote the overgrowth of non-susceptible bacteria and fungal pathogens (e.g., Candida).
- Pregnancy & Lactation: FDA Pregnancy Category B. Amoxicillin is excreted in breast milk in small amounts; monitor infants for loose stools, diaper rash, or thrush.