What over‑the‑counter stool softener and laxative options are available in Australia for an adult, and what is the recommended dosing and sequence of use?

Australian OTC Stool Softener vs Laxatives

Start with polyethylene glycol (PEG/Movicol) as your first-line agent for chronic constipation, not a stool softener like docusate. 1, 2

First-Line Treatment Algorithm

Polyethylene glycol (PEG) should be your go-to initial therapy:

• Available in Australia as Movicol or similar macrogol preparations
• Grade A recommendation with strong evidence for improving stool frequency and consistency 1, 2
• Start with standard dosing (typically 1-2 sachets daily) and adjust based on response
• Response is durable over 6 months 1
• Common side effects: abdominal distension, loose stool, flatulence, nausea 1

Why not stool softeners first? Docusate sodium (Coloxyl), the main OTC stool softener in Australia, is inferior to fiber supplements like psyllium for both stool softening and laxative efficacy 3. The evidence simply doesn't support stool softeners as first-line therapy.

Second-Line Options

If PEG fails or is not tolerated, consider:

Magnesium oxide:

• Grade B evidence supporting use 4, 2
• Start at lower dose and titrate up as needed
• Critical caveat: Avoid in renal insufficiency due to hypermagnesemia risk 1
• Trial duration in studies was 4 weeks, but longer-term use is appropriate 1

Fiber supplements (psyllium/Metamucil):

• Can be used alone for mild constipation or combined with PEG 1
• Grade B evidence 4, 2
• Superior to docusate for stool softening 3

Rescue/Short-Term Stimulant Laxatives

For occasional use or rescue therapy:

Bisacodyl or sodium picosulfate (Dulcolax, Pico-Salax):

• Strong recommendation with moderate evidence 1
• Grade A evidence for efficacy 4, 2
• Use short-term (≤4 weeks daily) or as rescue therapy 1
• Excellent option in combination with other agents 1
• Side effects: abdominal pain, cramping, diarrhea 1

Senna (Senokot):

• Grade A recommendation as first-line option 4, 2
• Conditional recommendation from guidelines 1
• Start at lower dose than studied (trial doses were higher than typical practice) and increase if no response 1
• While studied for 4 weeks, longer-term use is probably appropriate 1

Third-Line: If OTC Agents Fail

Lactulose:

• Use only after OTC therapies fail or are not tolerated 1
• Major limitation: Bloating and flatulence are dose-dependent and common, often limiting clinical use 1

Practical Sequencing for Australian Practice

1. Start: PEG (Movicol) - adjust dose to effect
2. Add if needed: Fiber supplement (psyllium) for combination therapy
3. Alternative if PEG fails: Magnesium oxide (check renal function first)
4. Rescue therapy: Bisacodyl or senna for breakthrough constipation
5. Last resort OTC: Lactulose if other options fail

What NOT to Use First

Avoid docusate (Coloxyl) as first-line therapy - despite being marketed as a stool softener, it has inferior efficacy compared to both PEG and fiber supplements 3. The Australian postcolostomy study that used liquid paraffin (Agarol) as a stool softener 5 is not generalizable to routine constipation management and these products have limited evidence.

Key Clinical Pitfalls

• Don't assume "stool softener" means better tolerability - PEG is well-tolerated and more effective
• Don't use magnesium products without checking renal function
• Don't avoid stimulant laxatives due to outdated concerns about dependency - they're safe for short-term and rescue use 1
• Don't continue ineffective therapy - if no response to adequate PEG dosing after 2-4 weeks, move to alternatives