What are the methods used in the preparation of Parenteral Products?

Filling

Solutions sterilized by filtration are to be filled under aseptic conditions. The containers and closures must be properly cleaned, sterilized and made available for use at this point in the process.

Filling consists of transferring a quantity of the product measured with precision and accuracy from a bulk container to a unit container. The transferring device should not contribute any contamination and the product at this stage should be adequately protected so that it does not pick up any particulate or microbial contamination from the environment.

Modern day automatic high speed filling machines can fill up to 300 or more containers per minute. As a safeguard against the entry of particulate matter in a product during filling, a final filter is often inserted in the system between the filter and the delivery tube.

Sealing

Sealing of the filled container should be done as soon as possible to prevent the contents from being contaminated. Sealing represents the final aseptic procedure. Ampoules are sealed by melting a portion of the glass neck with a fine jet of flame.

For rapid sealing, a high temperature gas-oxygen flame is most suitable. A variety of automated sealing devices are available today. For making ‘pull-seals’, the neck of the ampoule is heated below the tip leaving most of the tip for grasping with forceps or other mechanical devices.

The ampoule is constantly rotated in the flame from a single burner to soften the glass and then the tip is grasped firmly and pulled quickly away from the body of the ampoule which still continues to rotate. A small capillary tube is formed which is closed by twisting. Although pull-sealing is slow yet the seals are more perfect than tip sealing.

Vials and bottles are sealed by closing the opening with a rubber closure which is held in position by means of aluminium caps. An intact aluminium cap is the proof that the closure has not been removed. Single layered aluminium caps may be applied by means of a hand crimper while double or triple layered caps are crimped by means of heavy duty mechanical crimpers.

Sterilization

Sterilization is process of complete destruction or removal of all forms of life. Except in case of thermolabile substances, parenteral products are commonly sterilized after filling and sealing in the final containers and the process is called terminal sterilization.

Injections are sterilized by following methods :

1. Moist heat sterilization

2. Dry heat sterilization

3. Filtration through bacteria proof filters

4. Using aseptic techniques

Thermolabile preparations should be sterilized by non-thermal methods. Thermo-labile solutions are mostly sterilized by filtration through bacteria proof filters.

Other thermo-labile preparations like colloids, oleaginous solutions, suspensions and emulsions may require a process of sterilizing each component separately and the product is processed under aseptic conditions. Sterilization by radiation is another non-thermal method.

Dry solids such as penicillin, streptomycin, polyvitamins and certain hormones can be effectively sterilized by ionized radiations. Gaseous sterilization is no good when a glass container or other impervious barrier prevents the gas from permeation to the material.

Dry heat sterilization is also of limited application because the materials being sterilized by this method should not be adversely affected by the elevated temperatures.

Most useful sterilization method is autoclaving which employs steam under pressure. It is probably the most effective method for sterilization of aqueous liquids or substances that can be reached or penetrated by steam.

This method is ineffective under anhydrous conditions like a sealed ampoule containing dry solid or anhydrous oil. To prevent subsequent contamination after sterilization, the materials subjected to autoclaving must be wrapped or covered but this is not necessary in case of parenterals.

Solutions as they are already sealed. The effectiveness of sterilization method should be verified from time to time. Biological indicators are a useful tool for ascertaining the effectiveness of this method.

Aseptic Technique

Aseptic technique is defined as procedures that will minimize the chance of contamination with micro-organisms. Contaminants may be brought into the aseptic area by equipment, supplies, or people, so it is important to control these factors during preparation. A number of simple guidelines should be followed:

1. Before using the laminar air flow hood the operator should wash his hands with a suitable antimicrobial / detergent at the beginning of their work and when re-entering the aseptic preparation area.

2. Gown, gloves or mask if needed thereof should be sterilised.

3. Activities unrelated to product preparation should be kept to a minimum.

4. Eating or drinking, or the storage of food, or personal items should not be allowed in the aseptic area.

5. One person should working in the hood at a time.

6. All items that will be used during preparation should be checked for defects and expiry dates prior to use.

7. All non-sterile item surfaces should be disinfected prior to being placed into the hood.

8. All items necessary for the preparation should be placed into the hood prior to commencing the procedure.

9. Direct contact between a sterile product and any non-sterile product should be avoided.

10. All non-sterile surface areas should be swabbed with alcohol (70% isopropyl) and left ‘ for 30 seconds.

11. Ampoules and vials should be opened and contents aspirated using appropriate techniques to avoid particulate contamination.

12. Reconstituted powders should be mixed carefully according to manufacturer’s recommendations to ensure complete dissolution of the drug.

13. Needle entry into vials with rubber stoppers should be done at a 45° angle to minimize rubber core particulates.

14. All finished products should be carefully inspected after preparation for visible precipitation.

15. Each prepared sterile product should be assigned an expiry date based upon available data.

Small Volume Parenterals (SVPs):

Small volume of parenterals include ampoules of 1 ml, 2 ml, 3 ml, 5, ml up to 20 ml and vials of 1 ml, 2 ml, up to 30 ml. They are administered by various routes such as intramuscular, intravenous, subcutaneous, intraspinal, intracisternal, intrathecal etc.

Large Volume Parenterals (LVPs):

LVPs contain 100 ml and more of injectable solution. They are generally administered by intravenous route. Two types of solutions are available in the market.

Electrolytes:

Sodium chloride and potassium chloride solutions, etc Non-electrolytes : Dextrose and mannitol solutions, etc

Powder Parenterals:

Dry powders are available in the market. They are soluble in water for injection or in another sterile solvent just prior to use. They are available in the form of vials containing rubber closure and sealed with aluminium file. Following antibiotics are available in the form of dry powder e.g. penicillin, ampicillin, chloramphenicol, amoxycillin, sterptomycin, etc.

Cleaning and Sterilization of Vials

1. Vials are cleaned and sterilized before filling. Following procedure is used for cleaning • and sterilization of vials.

2. Soak the vial with detergent solution overnight to remove any sticking particles, grease, etc.

3. Wash with tap water three to four times till soap solution is completely removed.

4. Remove surface alkalinity using 1.0% hydrochloric acid solution.

5. Again wash the vial using tap water till free from alkalinity.

6. Rinse with de-ionized water and finally with distilled water.

7. Cleaned vials are sterilized by dry heat sterilization at 200°C for 4 hours.

8. Cool sterilized vials at room temperature under the closed condition prior to filling the vials.

9. Cleaning and Sterilization of Rubber closures

10. Rubber closures are boiled with 1.0% solution of liquid detergent for 30 minutes.

11. Wash with tap water till free from detergent.

12. Boil for 30 min. using 1.0% solution of hydrochloric acid.

13. Wash to make them free from acid.

14. Boil the acid washed rubber closures with 1.0% sodium carbonate solution and wash till free alkali.

15. Treat rubber stoppers with double strength bacteriostatic solution.

16. Wash three to four times using pyrogen free water.

17. Sterilize by autoclave at 115°C for 30 minutes.

Exercise 1: To prepare Water for Injection (WFI)

WFI can not be prepared by simple distillation method because in that case the pyrogens may enter mechanically into the condenser and ultimately into the receiver. Injection of distilled water may cause rise in body temperature due to the presence of pyrogens. Water, which increases body temperature, is known as apyrogenic.

It can also cause chills, pains in back and legs. Pyrogens are metabolite end products of bacteria. They are non-filterable, thermo-stable, and non-volatile in nature. The pH of water for injection should be as near as possible to pH 7.0.

It should also be free from carbon dioxide because slight acidity of WFI is sufficient to precipitate the alkaloidal salts like phenobarbitone and sulphonamides. Water for injection should be free from dissolved air. It is necessary to prevent sensitive medicament from oxidation.

Method of Preparation:

Distilled portable water from a neutral glass or metal still fitted with an efficient device from preventing the entrapment of droplets.

The first portion of distillate should be rejected and remaining amount of water should be collected in suitable container and immediately sterilized by heating in an autoclave or by filtration without addition of a bacteriostatic.

Exercise 2: To prepare Ascorbic acid injection

Method of Preparation:

Dissolve ascorbic acid slowly under constant stirring and nitrogen bubbling and add sodium bicarbonate with slow stirring. Separately prepare solution of sodium hydrosulphite in small proportion of WFI and add in the solution, add solution of disodium edetate and mix uniformly.

The pH is adjusted to 5.5 to 6.5 using sodium hydroxide solution or ascorbic acid solution. Make up the volume and mix with water for injection. Sterilize by passing through sterilized 0.22 µm membrane filter into sterilized filling vessel. Aseptically fill 5.3 ml in sterilized 5 ml amber colour ampoules.

Exercise 3: To prepare Dextrose Injection

Dextrose Injection is a sterile solution of anhydrous dextrose or an equivalent quantity of| dextrose monohydrate for parenteral administration. If the concentration of the solution is not reported, a 5% w/v solution should be prepared because it is isotonic with blood serum. Dextrose decomposes on heating. The rate of decomposition depends on sterilization temperature, duration of sterilization and presence of other substances. Decomposition of dextrose is reduced by adjusting the pH between 3.5 to 6.5 with hydrochloric acid; heating time should be minimum and over heating should be avoided. It should be cooled as quickly as possible after sterilization of the solution. Solution should not adhere to the neck of ampoules because it gets charred during the process of sealing. Injection should not be used if it contains a precipitate or any suspended particle

Dextrose 5.0 g

WFI 100.0 ml

Method of Preparation:

Dissolve the weighed quantity of dextrose in WFI and add sufficient WFI to produce 100 ml. The ampoules are sealed and sterilized immediately by autoclaving.

Exercise 4: To prepare Sodium Chloride Injection

Sodium chloride 0.9 g

WFI, qs 100.0 ml

Method of Preparation:

Dissolve sodium chloride in sufficient quantity of WFI and add sufficient WFI to produce 100 ml. Fill the solution into the ampoules and seal them. Sterilize by autoclaving as quickly as possible. Sterilization can also be done by filtration.

Exercise 5: To prepare Calcium Gluconate Injection

Calcium gluconate .0 g

Calcium D-saccharate 1.75 g

WFI, qs 100.0 ml

Method of Preparation:

Dissolve calcium gluconate in WFI and add calcium D-saccharate in solution. Adjust the pH between 6.0 to 8.2 using 10% solution of sodium hydroxide. Filter through 0.45 µm membrane filter. Sterilize by autoclave at 121°C for 30 minutes.

Exercise 6: To prepare Chloramphenicol Injection

Method of Preparation:

Add chloramphenicol in hot propylene glycol and stir till dissolved, add lignocaine base and dissolve with continuous stirring. Dissolve chlorocresol and lignocaine I hydrochloride separately in distilled water and add in the solution and stir well. Add sufficient propylene glycol to produce sufficient volume up to 100 ml. Adjust pH of the solution between 6.5 to 6.8. Filter the solution by vacuum filtration using Whatman filter paper No.1 and then pass through G-3 sintered glass funnel. Aseptically fill 10.5 ml of solution in dry sterile 10 ml j amber color vials with washed sterile butyl grey plugs and seal.

Exercise 7: To prepare Cyanocobalamin Injection

Method of Preparation:

Dissolve cynocobalmin in WFI and add benzyl alcohol and mix. Add sodium chloride, and sodium dihydrogen phosphate separately in WFI. Add the solution to the mixture of vitamins. Adjust pH between 4.0 to 5.5. Fill aseptically in 10 ml amber color vials.

Exercise 8: To prepare Dextrose with Sodium Chloride Solution

Dextrose5.0%

Sodium chloride0.9%

Activated charcoal5.0%

WFI, qs 100.0 ml

Method of Preparation:

Dissolve excess amount of dextrose in WFI and add activated charcoal and other additives, filter and sterilize by autoclaving.

Exercise 9: To prepare Compound Sodium Chloride Injection

Sodium chloride 0.86 g

Potassium chloride 0.030 g

Calcium chloride hydrated 0.033 g

WFI, qs 100.0 ml

Method of Preparation:

Dissolve sodium chloride, potassium chloride, calcium chloride hydrated in WFI and add sufficient WFI to produce 100 ml. Filter the solution and immediately sterilize by autoclave. It can be sterilized by filtration.

Exercise 10 To prepare Sodium Citrate Anticoagulant Injection

Sodium citrate 4.0 g

WFI qs 100.0 ml

Method of Preparation:

Dissolve the sodium citrate in 90 ml of water for injection. Filter and add sufficient water for injection to produce 100 ml, immediately sterilize by heating in an autoclave or by filtration.