SOP applies to the Analytical Method Development (AMD) department involved in the formulation, development, and evaluation of isotonicity in sterile pharmaceutical products including parenterals, ophthalmic drops, and irrigation solutions.

3. Responsibilities

• Analytical Scientist: Develops and validates the method for tonicity evaluation.
• QC Analyst: Performs routine testing once the method is approved.
• QA Executive: Reviews results and ensures adherence to regulatory requirements.

4. Accountability

The Head of Analytical Method Development is accountable for ensuring validated tonicity test methods are implemented and aligned with safety and quality objectives for parenteral and ophthalmic products.

5. Procedure

5.1 Tonicity Testing Methods

1. Osmolality Measurement: Conducted as per SOP/AMD/269/2025 using a freezing point depression osmometer.
2. Hemolysis Test (for injectables):
   • Mix human red blood cells (RBCs) with test solution and incubate at 37°C for 30 minutes.
   • Compare with isotonic (0.9% NaCl) and hypotonic (distilled water) controls.
   • Absorbance measured at 540 nm; % hemolysis calculated.
3. Tissue Irritation/Discomfort Index (for ophthalmics):
   • Instill product into rabbit eye (in preclinical setup) or use ex vivo corneal tissue models.
   • Evaluate signs of discomfort, hyperemia, or corneal opacity.
   • Score irritation against USP and OECD guidelines.

5.2 Sample Handling

1. Use sterile containers and aseptic technique throughout sample preparation.
2. Maintain physiological temperature during biological evaluations (37°C).

5.3 Acceptance Criteria

• Osmolality: 270–310 mOsm/kg H₂O
• Hemolysis: ≤5% hemolysis compared to positive control
• Ocular Irritation Score: Non-irritant or minimal transient irritation only

5.4 Method Validation Parameters

1. Specificity: Must differentiate between isotonic and hypo/hypertonic responses.
2. Precision: RSD ≤2% for biological replicates.
3. Robustness: Stability of erythrocyte suspension or tissue response under varied conditions.

6. Abbreviations

• RBC: Red Blood Cells
• OECD: Organisation for Economic Co-operation and Development
• QA: Quality Assurance
• AMD: Analytical Method Development

7. Documents

1. Tonicity Test Log – Annexure-1
2. Hemolysis Test Worksheet – Annexure-2
3. Validation Summary Report – Annexure-3

8. References

• USP <785>: Osmolality and Tonicity
• OECD 405: Acute Eye Irritation/Corrosion
• ICH Q2(R1): Validation of Analytical Procedures

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name	Rahul Nanda	Poonam Iyer	Sunita Reddy
Designation	Formulation Scientist	QA Reviewer	Head – AMD
Department	Analytical Method Development	QA	Analytical Method Development

11. Annexures

Annexure-1: Tonicity Test Log

Sample ID	Osmolality (mOsm/kg)	Hemolysis (%)	Ocular Irritation Score	Status
INJ-270-01	289	2.1	Non-irritant	Pass

Annexure-2: Hemolysis Test Worksheet

Sample	Absorbance	Hemolysis (%)	Control Absorbance	Status
INJ-270-01	0.121	2.1	5.68	Pass

Annexure-3: Validation Summary Report

Tonicity testing method was validated for injectable and ophthalmic dosage forms. Accuracy and biological response assessment confirmed specificity and sensitivity. Method deemed robust for use in routine QC, formulation screening, and stability studies.

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
21/05/2025	2.0	Added ocular testing protocol and updated validation details	Annual Review	Sunita Reddy
05/03/2022	1.0	Initial Release	New SOP	QA Head