Fish Antibiotics and Human Equivalents: Reference Table

Critical Warnings Before the Table

1. Do not use antibiotics for viral illness. Most upper respiratory infections, influenza, and most "colds" are viral. Antibiotics have zero effect. Using them wastes your supply and disrupts gut microbiome.

2. Allergy check first. Penicillin allergy affects 10% of the population. Anaphylaxis is possible. Know your allergy status before needing antibiotics.

3. Complete full courses. Stopping early because you "feel better" leaves resistant bacteria behind and is a leading cause of treatment failure and antibiotic resistance.

4. These are last-resort measures. Access a physician, clinic, or pharmacist with a prescription whenever possible. This guide exists for scenarios where that access is genuinely unavailable.

5. Avoid tetracyclines past expiration. Outdated tetracyclines develop epianhydrotetracycline, a compound that causes Fanconi syndrome (severe kidney toxicity). Other antibiotics can be used past expiration with reduced potency; tetracyclines cannot.

Fish Antibiotic to Human Equivalent Table

| Fish Product Name | Active Ingredient | Human Equivalent | Typical Capsule Dose | Available From | |-------------------|------------------|-----------------|---------------------|----------------| | Fish Mox | Amoxicillin | Amoxicillin | 250mg or 500mg | Pet stores, online | | Fish Mox Forte | Amoxicillin | Amoxicillin | 500mg | Pet stores, online | | Fish Cillin | Ampicillin | Ampicillin | 250mg | Pet stores, online | | Fish Flex | Cephalexin | Keflex | 250mg or 500mg | Pet stores, online | | Fish Flex Forte | Cephalexin | Keflex | 500mg | Pet stores, online | | Fish Zole | Metronidazole | Flagyl | 250mg | Pet stores, online | | Fish Pen | Penicillin V | Penicillin VK | 250mg or 500mg | Pet stores, online | | Fish Doxy | Doxycycline | Vibramycin | 100mg | Pet stores, online | | Fish Cin | Clindamycin | Cleocin | 150mg | Pet stores, online | | Fish Cycline | Tetracycline | Tetracycline | 250mg or 500mg | Pet stores, online |

Note: Product availability changes frequently. Verify before relying on a specific product being in stock.

Antibiotic Indications Reference

Amoxicillin (Fish Mox) — Adult 500mg 3x/day × 7-10 days

Treats:

• Strep throat (group A Strep pharyngitis)
• Ear infections (otitis media)
• Dental infections
• Sinusitis (bacterial, prolonged >10 days)
• Urinary tract infections (E. coli often resistant — check local resistance patterns)
• Lyme disease early stage (alternative: doxycycline is preferred)

Does NOT treat:

• MRSA (methicillin-resistant Staph aureus)
• Gram-negative rods (Pseudomonas, Klebsiella)
• Viral infections
• Anaerobic infections (add metronidazole or use amoxicillin-clavulanate if available)

Contraindication: Penicillin allergy

Amoxicillin-Clavulanate (Not available as fish antibiotic, but Augmentin is a common prescription)

Treats: All amoxicillin indications + animal bites, infected wounds with mixed flora, sinusitis with treatment failure.

Cephalexin (Fish Flex) — Adult 500mg 4x/day × 7-10 days

Treats:

• Skin and soft tissue infections (cellulitis, impetigo)
• Wound infections (non-MRSA)
• Strep throat (penicillin-alternative)
• Bone infections (osteomyelitis from Staph/Strep)

Does NOT treat:

• MRSA
• Gram-negative organisms
• Abdominal infections

Note: Cephalosporins have approximately 1-2% cross-reactivity with penicillin allergy. Use with caution in penicillin-allergic patients; avoid if the penicillin reaction involved anaphylaxis.

Doxycycline (Fish Doxy) — Adult 100mg 2x/day × 7-10 days (varies by condition)

Treats:

• Tick-borne illnesses: Lyme disease (21 days), Rocky Mountain Spotted Fever (7 days), ehrlichiosis, anaplasmosis
• Community-acquired pneumonia (atypical — Mycoplasma, Chlamydia pneumonia)
• Urinary tract infections (when amoxicillin-resistant)
• Sexually transmitted infections (chlamydia, gonorrhea with ceftriaxone, syphilis)
• Malaria prevention (100mg/day, start 1-2 days before, continue 4 weeks after exposure)
• Anthrax exposure prophylaxis
• Skin infections (acne, rosacea)

Broad-spectrum across gram-positive, gram-negative, and atypical organisms. One of the most useful antibiotics to stockpile for diverse scenarios.

Contraindications: Pregnancy (causes fetal bone/tooth damage), children under 8 (same reason). Causes photosensitivity — sun protection important.

Food: Take with food to reduce GI irritation. Avoid calcium, antacids, and iron within 2 hours (chelation reduces absorption).

Critical: Do not use past expiration date. See warning above re: tetracycline degradation.

Metronidazole (Fish Zole) — Adult 500mg 3x/day × 7-10 days

Treats:

• Anaerobic bacterial infections (dental abscess, intraabdominal infections, pelvic infections)
• Bacterial vaginosis (500mg 2x/day × 7 days)
• Giardia and other intestinal parasites (2g single dose or 250mg 3x/day × 5 days)
• C. difficile infection (250mg 4x/day × 10 days)
• Trichomoniasis (2g single dose)
• H. pylori eradication (combined with amoxicillin and a PPI)

Does NOT treat:

• Aerobic bacteria
• Respiratory infections
• Urinary tract infections

Important: Do not drink alcohol during treatment or for 48 hours after last dose. Metronidazole inhibits acetaldehyde dehydrogenase, causing a severe disulfiram-like reaction with alcohol (nausea, vomiting, flushing, rapid heart rate).

Clindamycin (Fish Cin) — Adult 300-450mg 4x/day × 7-10 days

Treats:

• Skin and soft tissue infections including MRSA (community-acquired MRSA strains are often clindamycin-susceptible — TMP-SMX is preferred when available)
• Dental and oral infections (excellent penetration into oral/dental tissues)
• Aspiration pneumonia and lung abscess
• Bone infections
• Pelvic inflammatory disease (combined with other agents)

Does NOT treat:

• Gram-negative organisms
• Enterococcus

Important: Associated with C. difficile colitis — a serious complication of antibiotic use. Risk is higher with clindamycin than most other antibiotics. Discontinue if severe diarrhea develops during treatment.

Cephalexin vs. TMP-SMX for MRSA

Community-acquired MRSA (CA-MRSA) is now common enough that any skin abscess or cellulitis should be assumed MRSA until proven otherwise. Cephalexin does NOT treat MRSA.

Trimethoprim-sulfamethoxazole (TMP-SMX / Bactrim) is not available as a fish antibiotic but is the preferred oral agent for CA-MRSA. It is inexpensive as a prescription medication and worth specifically requesting from your physician for your emergency stockpile if you have no allergy (sulfa allergy is common — verify).

For skin MRSA without TMP-SMX: doxycycline has activity against CA-MRSA for many strains and is a reasonable alternative.

Storage

Most antibiotic capsules/tablets:

• Cool, dry, dark location (59-77°F/15-25°C)
• Original sealed container
• Shelf life: 1-3 years past manufacture date in optimal conditions
• FDA SLEP data suggests most retain potency 2+ years past expiration with proper storage

Exceptions requiring strict expiration observation:

• Tetracycline and doxycycline: strict 2-year limit. Degradation products are nephrotoxic.
• Liquid antibiotics: 14 days refrigerated once reconstituted. Do not stockpile premixed liquids.
• Any antibiotic with visible color change, crystal formation, or odor change: discard

Antibiotic Allergy Cross-Reference

| Drug Class | Common Example | Cross-Reactivity | |------------|---------------|------------------| | Penicillins | Amoxicillin, ampicillin, penicillin V | Cross-react with each other; 1-2% cross-react with cephalosporins | | Cephalosporins | Cephalexin | 1-2% cross-react with penicillins; do not use in penicillin anaphylaxis history | | Sulfonamides | TMP-SMX (Bactrim) | Cross-react with each other; not related to "sulfa-containing" drugs like loop diuretics | | Macrolides | Azithromycin | No cross-reactivity with other classes | | Fluoroquinolones | Ciprofloxacin, levofloxacin | Rare class-wide reactions | | Metronidazole | Flagyl | Isolated class; no common cross-reactions | | Clindamycin | Cleocin | Isolated class |