Clinical beta

FMBM is currently in clinical beta. Content is for professional review/testing and must not replace local protocols, senior clinical judgment, or official prescribing references.

Drug Monograph

Ethambutol

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Ethambutol

Antitubercular (PO)

TBOptic neuritis

Indication

Active TB intensive + continuation β€’ MAC prophylaxis historical

At a glance

INDICATIONS (CORE USE)

**TB combination** β€” **optic neuritis** (red-green discrimination); **renal adjust**; **pregnancy relatively safer** than pyrazinamide for ocular monitoring.

ADULT DOSE (STANDARD)

15–25 mg/kg PO daily; max 1.6 g/day some references

MAX DOSE

~1.6–2 g/day weight cap

Route

PO

PEDIATRIC DOSE

15–25 mg/kg/day β€” young children cannot report vision β€” baseline difficulty

Do not miss

Must-not-miss safety points

Major warning

- **Optic neuritis** β€” baseline visual acuity/color; stop if symptoms - Renal failure accumulation β†’ ↑ ocular risk β€” dose reduce - Not monotherapy

Indications

USE IF: TB regimen component (especially initial unknown resistance patterns). AVOID IF: Cannot monitor vision (communicate with ophtho for young children), unconscious patient long-term without eye exams.

Primary

  • Active tuberculosis combination therapy (especially initial phase before susceptibility)

Secondary

  • Mycobacterium avium complex treatment β€” specialist high-dose prolonged

Dosing

STANDARD (ADULT PO)

15 mg/kg PO daily (usual) β†’ 25 mg/kg daily initial phase if drug resistance suspected

ADULT DOSE

15 mg/kg daily standard; 25 mg/kg if suspected drug resistance initial phase β€” max per program

PEDIATRIC DOSE

mg/kg β€” ophtho involvement if preverbal.

MAX DOSE

Institution caps ~1.6 g

Practical Note

CrCl <30 β†’ 15 mg/kg q24–48h per label tables.

Warnings

Clinical warnings

  • Peripheral neuropathy less common than INH

Adverse effects

  • retrobulbar neuritis
  • hyperuricemia
  • rash

Contraindications

  • Known optic neuritis from ethambutol
  • Unable to monitor vision when high-dose prolonged

Drug interactions

  • Aluminum antacids ↓ absorption β€” separate

Special populations

Pediatrics

15–25 mg/kg/day β€” young children cannot report vision β€” baseline difficulty

Pregnancy

Generally continued in TB pregnancy

Lactation

compatible.

Renal impairment

**Mandatory** reduction dialysis schedules. **CrCl scaffold (FMBM β€” titrate to FDA/SFDA label + institutional pharmacy nomogram):** - **CrCl β‰₯50** β†’ standard mg/kg daily - **CrCl 10–50** β†’ intermediate interval per label tables (often approach q24–48h as GFR falls) - **CrCl <10** β†’ **~15 mg/kg q24–48h** per label; ↑ **optic** risk if accumulated

Hepatic impairment

No major adjustment.

Elderly

Renal + vision baseline.

Administration

PO once daily.

Monitoring

  • Monitor: - High dose or renal impairment β†’ **visual acuity / color vision** per schedule - Renal impairment β†’ **dosing interval** per CrCl tables - Snellen + red-green testing baseline monthly if >15 mg/kg or renal impairment - Renal function drives dose
  • Recheck: - No clinical improvement at 48–72h β†’ reassess diagnosis, resistance, source control, and drug interactions - If targets not met after reassessment of dose, organ function, and interactions β†’ escalate per protocol (DO NOT continue blindly)

Overdose / toxicity

Clinical Picture

**Life-threatening (first):** **rapid bilateral vision loss** (optic toxicity). **Secondary:** dose-related color vision loss.

Immediate Actions

Stop β†’ urgent ophthalmology if visual symptoms

Antidote

No specific antidote; treat complications (e.g. anaphylaxis β†’ epinephrine per ACLS)

Decontamination

Supportive

Escalation

Rapid vision loss β†’ urgent specialty / **ICU** if secondary complication; **severe renal accumulation β†’ consider hemodialysis** for clearance discussion β€” pharmacy

Clinical pearls

Common mistakes, resistance logic, and bedside traps

High-Yield Summary

**Color vision** and **visual acuity** are the price of TB therapy. **Renal failure** β†’ drug hangs around β†’ **eyes pay**. Kids need ophtho help.

Clinical pearls

RIPE: ethambutol can be dropped when susceptibility returns if fully susceptible β€” program. MAC: months-years therapy β€” ophtho surveillance mandatory. *Stewardship (all antimicrobials):* Empiric choice β†’ syndrome severity + **local antibiogram**; shortest effective course.

Stewardship & safety

  • Monthly vision high dose
  • Renal adjust
  • Stop if scotoma

Pharmacy Tool

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Ethambutol 25 mg/mL oral suspension

suspension Β· oral

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Pharmacokinetics

Renal elimination; penetrates meninges moderately.

Mechanism of action

Inhibits arabinosyl transferases in mycobacterial cell wall.

Common brand names

Global data (no country-specific data available)

Saudi Arabia

(placeholder β€” verify local formulary)

Common trade names are curated examples only β€” formulations and availability vary. Verify the exact product name with your local pharmacy and national regulator before prescribing or dispensing.

Country practice notes

  • Empiric choice β†’ tie to syndrome, severity, and local antibiogram β€” not habit.
  • IV β†’ PO step-down when oral bioavailability and susceptibility allow.
  • Do not use antibiotics for uncomplicated viral illness β€” stewardship.

References

Saudi Arabia

  • SFDA (Saudi Food & Drug Authority)
  • Saudi National Formulary / MOH (where available)

International

  • WHO Model List of Essential Medicines (verify current edition)
  • US FDA or EU EMA product information (when national SmPC is unavailable)
  • Sanford Guide
  • IDSA / ESCMID (indication-specific)
  • Local antimicrobial stewardship / hospital formulary
  • FDA / SFDA / regional product labeling
  • Sanford Guide
  • IDSA / ESCMID (indication-specific)
  • Local antimicrobial stewardship / hospital formulary
  • FDA / SFDA / regional product labeling

Do not miss

  • Uncomplicated viral URI/bronchitis β†’ antibiotics rarely indicated
  • Narrow or stop when susceptibilities + clinical stability allow
  • Patient on ethambutol reports β€œcolors look washed out” β†’ stop + urgent eye exam.
  • Underdosing in TB meningitis β€” follow mg/kg meningitis protocols.
  • Monthly vision high dose
  • Renal adjust
  • Stop if scotoma