# Drug Interactions Reference

Common drug interactions. When multiple drugs are prescribed together, check this list.

> **Note**: This is a quick-reference guide, not a comprehensive medical database. Always verify with authoritative sources.

## Critical Interactions (Avoid Together)

| Drug A | Drug B | Risk | Action |
|--------|--------|------|--------|
| Macrolides (克拉霉素/阿奇霉素) | Statins (他汀类) | Rhabdomyolysis | Avoid together, or pause statin |
| Macrolides (克拉霉素) | Anticoagulants (华法林) | Bleeding risk ↑ | Monitor INR, adjust dose |
| Fluoroquinolones (左氧氟沙星/莫西沙星) | NSAIDs (布洛芬) | Seizure risk ↑ | Avoid together |
| Cephalosporins (头孢类) | Alcohol | Disulfiram-like reaction | No alcohol during + 7 days after |
| Metronidazole/Tinidazole (甲硝唑/替硝唑) | Alcohol | Disulfiram-like reaction | No alcohol during + 3 days after |
| Fluoroquinolones | Calcium/Iron/Magnesium/Aluminum | Absorption ↓ | Separate by 2+ hours |
| Azithromycin | Antiarrhythmics | QT prolongation | ECG monitoring |
| Montelukast (孟鲁司特) | Rifampicin/Phenobarbital | Blood concentration ↓ | Avoid together |

## Moderate Interactions (Monitor)

| Drug A | Drug B | Risk | Action |
|--------|--------|------|--------|
| Ibuprofen | Aspirin | GI bleeding | After meals, short-term use |
| Paracetamol | Other paracetamol-containing products | Hepatotoxicity | Max 4g/day total |
| Probiotics | Antibiotics | Probiotic inactivation | Separate by 2+ hours |
| Smectite powder (蒙脱石散) | Other oral drugs | Absorption affected | Separate by 1-2 hours |
| Spironolactone | ACEI/ARB | Hyperkalemia | Monitor blood potassium |
| Clarithromycin | Theophylline | Theophylline concentration ↑ | Monitor blood levels |
| Montelukast | Erythromycin | Montelukast concentration ↑ | Watch for adverse effects |

## Common Combination Rules

| Scenario | Rule |
|----------|------|
| Antibiotics + Probiotics | Separate by 2 hours |
| Smectite + Other oral drugs | Separate by 1-2 hours |
| Cephalosporins/Metronidazole + Alcohol | Absolutely contraindicated |
| Paracetamol-containing products | Track total daily dose |
| Multiple cold/flu combos | Avoid ingredient overlap |
| Nasal steroid sprays (same class) | Don't use simultaneously — pick one |

## Special Drug Categories

### Antibiotics
- Complete the full course; do not stop early
- Check for allergies before prescribing
- Note: fluoroquinolones contraindicated in children <18

### Controlled Substances
- Flag 精二药品 (Class II psychotropics) — special management required
- No exceeding prescribed dose
- Avoid alcohol

### Pediatric Considerations
- Fluoroquinolones: contraindicated <18 years
- Aspirin for fever: contraindicated <12 years
- Codeine: contraindicated <12 years
- Always calculate dose by weight, not age

## Sources
- Micromedex Drug Interactions
- 中华人民共和国药典临床用药须知
- AAP Red Book