INTRODUCTION:

Intravenous (I/V) paracetamol formulation was first introduced in the hospital setting in 1985 and indicated when enteral administration is not possible. Paracetamol or acetaminophen is a drug of recognized analgesic and antipyretic properties, and constitutes as the drug of first choice for the treatment of pain and fever conditions in many groups of patients. In particular, paracetamol is a drug widely used in hospitals, where the compositions for intravenous administration are especially useful.

This route allows more rapid onset of the therapeutic action, and also a greater efficacy and a longer analgesic duration, in acute pain management in the hospital setting¹. Therefore, in this context, it is crucial to have a stable liquid formulations of paracetamol which are suitable for intravenous administration. However, the preparation of these kinds of solutions, ready for use by intravenous infusion, shows a number of difficulties, mainly due to the fact that phenolic active ingredients, are unstable in aqueous solution, since they are sensitive to oxidation by the oxygen dissolved in the medium. The presence of these degradation products can often be seen with the naked eye, since they give colour to the solution which, in optimal conditions, must be totally colourless. Thus, there exists several challenges in achieving stable aqueous solutions of paracetamol.² This research aimed to design and develop stable paracetamol LVP and SVP formulations taking into consideration all above challenges.

RATIONALE:

Paracetamol is poorly soluble in water. Its aqueous injectable formulations did not exist for long time owing to this fact as well as its stability in water³. Its challenging to design paracetamol aqueous formulations.⁴ This research made an attempt to study these challenges and patents related to it, in-order to design and develop stable LVP and SVP injectable formulations.

MATERIALS AND METHODS- PART 1:

1.1 Study of innovator’s formula and its patent:

United States Patent US8071619B2 has disclosed method for preparation of 1% Paracetamol aqueous solution formulation. The present invention relates to a novel injectable liquid pharmaceutical formulation of paracetamol containing a dimer as an active principle, and the use of this dimer for stabilizing a liquid pharmaceutical formulation of 1% paracetamol aqueous solution.²

Table No.1 : Formula available in patent:²

Name of Ingredient	Quantities in gm/100mL	Category
Paracetamol	1.0	Analgesic, Antipyretic
Monosodium Phosphate dihydrate	0.1002	Buffering agent
Disodium phosphate dihydrate	0.0785	Buffering agent
Sodium Chloride	0.65	Tonicity modifier
Water for injection	Up To 100 mL	Vehicle

1.2Formulation of product similar to Innovator (F1), 1% Paracetamol aqueous solution by Dimerization:

Table No.2 : Formula developed (F1):

Name of Ingredient	Quantities in gm/100mL	Category
Paracetamol	1.0	Analgesic, Antipyretic
Monosodium Phosphate dihydrate	0.1071	Buffering agent
Sodium Chloride	0.65	Tonicity modifier
Water for injection	Up To 100 mL	Vehicle

Following procedure was used for F1:

1. 1.0 gm of Paracetamol was weighed accurately.

2. Weighed paracetamol was transferred in to a conical flask & up to 80 % of total batch size, water for injection was added.

3. The resultant solution was heated at temperature of 70°C temp for 15 minutes.

4. pH of solution was maintained between 5.5 to 6 and tonicity was adjusted by adding specified amount of monosodium phosphate dihydrate and sodium chloride.

5. Volume was made up to 100 mL by adding water for injection.

1.3 Evaluation of F1:

1.3.1 Test for clarity:

The F1 was evaluated for its clarity using nephalo-turbidity meter. Following procedure was used for analysis.

Turbidimetric Analysis:

1. Turbidimeter was calibrated using standard NTU solutions.

2. Sample holder was rinsed three times with water for injection.

3. Turbidimeter sample holder was filled with water for injection.

4. Reading were noted for above blank

5. F1 was placed in sample holder and reading were noted.⁵

1.3.2 Assay:

Assay for F1 was performed using UV spectrophotometric method.⁶

1.3.3 Stability Study:

Stability study for F1 was carried out before and after sterilization.

1. Before sterilization F1 was allow to cool at 2-8°C and checked for clarity using Nephalo turbidity meter and assay was calculated using UV spectrophotometric method.

2. After sterilization stability study was carried out for one month at different temperature conditions. Clarity was checked using nephalo-turbidity meter and assay was performed using UV spectrophotometric method.⁷

1.3.4 Sterility testing.

Sterility testing was done by method B of Indian Pharmacopoeia 2018: Direct inoculation method as per the following procedure.

1. Culture medium (Fluid thioglycolate) and formulation was autoclaved for 121°C for 15 mins.

2. After autoclaving the medium was allowed to cool and was aseptically transferred into test tubes

3. One test tube was kept as negative control in which fluid thioglycolate medium was put and autoclaved.

4. One test tube was kept as positive control in which microbial cultures- namely S. aureus and Candida albicans were inoculated using sterile nichrome wire loop in fluid thioglycolate medium and soyabean casein digest medium respectively.

5. One test tube was used as a test in which sterile formulation F1was inoculated using sterile nichrome wire loop and fluid thioglycolates medium.

6. All the test tubes were put in the incubator at 37°C for 14 days.

7. During and after 14 days the observations for the presence of microorganisms were noted.⁸

2.1 Formulation and evaluation of 1% Paracetamol aqueous solution by Nanonization using probe sonicator (F2):

After studying and mimicking the innovators formula (1% Paracetamol drip by dimerization), research was continued to develop 1% paracetamol drip without involving heat. Technique adopted to achieve this was Nanonization using probe sonicator.⁹

Formulation of 1% Paracetamol aqueous solution by probe sonication F2

Table No. 3 : Formula developed (F2):

Name of Ingredient	Qty. in gm/100mL	Category
Paracetamol	1.0	Analgesic, Antipyretic
Citric acid	0.05	Buffering agent to get pH in the range 4.5-5.4
Sodium Chloride	0.65	Tonicity modifier
Butylated hydroxy anisole (BHA)	0.03 % w/v	Free radical scavenger- anti oxidant
Water for injection	Up to 100 mL	Vehicle

Following procedure was used for F2:

1. One gm Paracetamol was weighed accurately.

2. Weighed paracetamol was transferred in to a beaker and water for injection was added up to 80% of total batch size.

3. The resultant solution was sonicated using probe sonicator for facilitating dissolution.

4. Tonicity was adjusted by adding specified amount of sodium chloride and pH of solution was maintained between 4.5 to 5.4, by adding citric acid. Antioxidant was added at the end.

5. Volume was made up to 100 mL by adding water for injection.

6. Formula was filled in LVP bottle and autoclaved.

2.2 Evaluation of F2

2.2.1 Test for clarity:

Evaluation was performed as per F1

2.2.2 Assay:

Evaluation was performed as per F1

2.2.3 Stability Study:

Evaluation was performed as per F1

2.2.4 Sterility testing:

Evaluation was performed as per F1

MATERIALS AND METHODS- PART 2:

3.1 Study of innovator’s formula of 150 mg/mL Paracetamol injection and its patent:

United States Patent US 8, 178, 121 has discloses method for the preparation of ready-to-use 150 mg/mL Paracetamol injection, containing propylene glycol as the only cosolvent¹⁰

Table No.4 : Formula developed (F3):

Name of Ingredient	Quantities /10mL	Category
Paracetamol	1.5 gm	Analgesic, Antipyretic
Benzyl alcohol	0.2 mL	Preservative
Sodium Chloride	0.65 mL	Tonicity modifier
Propylene Glycol	6 mL	Solvents
WFI	to-- 10 mL	Vehicle

3.2 Formulation of 150 mg/mL Paracetamol injection by co solvency (F3)

Following procedure was used for F3:

1. 1.5gm of Paracetamol was weighed accurately.

2. Weighed paracetamol was transferred in to a beaker and sufficient amount of propylene glycol was added to it. This solution was heated at 60°C for 5 min and then allowed to cool.

3. The resultant solution was put in probe sonicator for facilitating dissolution.

4. Specified amount of benzyl alcohol and sodium chloride were added.

5. Specified amount (as given in formula) of propylene glycol was added and volume was made up to 10 mL using water for injection.

3.3 Evaluation of F3

3.3.1 Test for clarity: Evaluation performed similar to F1

3.3.2Assay: Evaluation perform similar to F1

3.3.3 Stability Study: Evaluation perform similar to F1

3.3.4 Sterility testing: Evaluation perform similar to F1

RESULTS AND DISCUSSION:

1.3 Evaluation of 1% Paracetamol aqueous solution by Dimerization (F1):

1.3.1 Test for clarity (F1): F1 observed to be clear

1.3.2Assay (F1): 99%

1.3.3 Stability Study (F1):

A) % Assay at temp 2-8°C and 60% RH

Before sterilization % Assay - 99.95%

After sterilization % Assay - 99.15%

B) % Assay at temp 25°C and 60% RH

Before sterilization % Assay - 99%

After sterilization % Assay - 98.5%

C) % Assay at temp 40°C and 60% RH

Before sterilization % Assay - 98.95%

After sterilization % Assay – 98 %

1.3.4 Sterility testing (F1):

A) F1 shows no turbidity

B) Nutrient media (Negative control) shows no turbidity.

C) Microbial culture (Positive control) shows turbidity.

Fig No.1: Test for sterility F1, Test sample -clear.

2.2 Evaluation of F2

2.2.1 Test for clarity (F2):

F2 observed to be clear.

2.2.2 Assay (F2):

99.95%

2.2.3 Stability Study (F2):

A)% Assay at 2-8°C and 60% RH

Before sterilization % Assay-99.95%

After sterilization % Assay-99.15%

B) % Assay at 25°C at 60% RH-

Before sterilization % Assay-99 %

After sterilization % Assay-98.5%

C) % Assay at 40°C at 60% RH-

Before sterilization % Assay-98.95 %

After sterilization % Assay-98%

2.2.4 Sterility testing (F2):

A)F2 showed no turbidity

B)Nutrient media (Negative control) showed no turbidity.

C)Microbial culture (Positive control) showed turbidity.

Fig No.2: Test for sterility foe F2, Test sample -clear.

RESULT AND DISCUSSION PART 2:

3.3 Evaluation of F3:

3.3.1 Test for carity (F3):

F3 observed to be clear.

3.3.2 Assay (F3):

99.95%

3.3.3 Stability Study (F3):

A) % Assay at 2-8°C and 60% RH

Before sterilization % Assay-99.25%

After sterilization % Assay-99.15%

B) % Assay at 25°C and 60% RH-

Before sterilization % Assay-99%

%After sterilization % Assay-98%.

C) % Assay at 40°C and 60% RH-

Before sterilization % Assay-98.75 %

After sterilization % Assay-97.75%

3.3.4 Sterility testing (F3):

A) F3 shows no turbidity

B) Nutrient media (Negative control) showed no turbidity.

C) Microbial culture (Positive control) showed turbidity.

Fig No.3: Test for sterility for F3, Test sample -clear.

CONCLUSION:

Paracetamol is ancient but widely used antipyretic drug. The dose of paracetamol and its solubility in water gives a challenge to develop it in to clear aqueous solution. Its stability in water also needs pH adjustment and protection from oxidation. There was always need and demand to design paracetamol into aqueous injectable dosage forms to address the emergency needs of high fever conditions. In this research different techniques of solubility enhancement were used and aqueous solution of paracetamol as stable LVP and SVP were prepared. The evaluation and stability study for F1, F2 and F3 supports the conclusion.

ACKNOWLEDGEMENT:

I extend a deep gratitude towards Founder president of Sinhgad Technical Education society Prof. M. N. Navale and Principal Dr. S. D. Sawant, S.T.E.S’s Smt. Kashibai Navale College of Pharmacy, Pune for their encouragement and support.

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Received on 06.07.2019 Modified on 08.08.2019

Research J. Pharm. and Tech 2020; 13(2):727-731.

DOI: 10.5958/0974-360X.2020.00138.9