Dry powder suspensions are commonly used for children after reconstitution, meaning these are filled in bottles in the form of powder or granules, and later on, a diluent, which is usually water, is added to shake and a suspension is prepared.
Drugs having stability issues in liquid media are prepared in the form of a dry powder suspension, and this technique enhances the drug stability as it is ready at the time of use.
How is dry powder suspension prepared?
Dry powder suspensions are prepared in the pharma either by the granulation process or by the simple mixing process.
If these are prepared by wet granulation method then all the steps are the same (which are used for tablet manufacturing) to prepare the final blend with the difference is that in case of tablets, the granulation blend is compressed to form tablets but in case of dry powder suspension the granulation blend is filled in bottles.
A filling machine is used to fill the predetermined quantity of granular blend in each bottle, and then these bottles are sealed and packed.
Reconstitution Process
Reconstitution process is used for dry powder suspensions where the defined quantity of diluent, usually water, is added in the bottle containing dry powder or granules.
The water is added up to the mark provided on the bottle to ensure the required level of active pharmaceutical ingredient in each ml.
Now a most commonly asked question is, how to calculate the API or active pharmaceutical ingredient for dry powder suspension?
API Calculation
To calculate the quantity of active pharmaceutical ingredients required to prepare a specific dosage form is a very important calculation, but most professionals & freshers don’t know how to calculate API or active pharmaceutical ingredient for tablets, capsules and dry powder suspension.
The API calculation for tablets and capsules is very simple, but the majority of the professionals working in pharma are not aware of the API calculation method for dry powder suspension because it is different from tablets and capsules.
In case of tablets and capsules, we have to calculate for a specific number of tablets or capsules, but in dry powder suspension, these calculations become tricky due to the involvement of API per ml.
If you are not aware of the calculation method for tablets and capsules, read in the following article,
In the current article, we will learn the API calculation method only for dry powder suspensions,
Calculation With Practical Explanation
Suppose that we want to prepare a dry powder suspension containing Ciprofloxacin HCl as active pharmaceutical ingredient. How much quantity of Ciprofloxacin HCl will be required to prepare a batch size with the following specifications?
- Number of bottles = 25000
- Filling Weight is = 25 gm
- Final Blend weight is = 625 kg
From the above information, we have no idea regarding the calculation of the required amount of Ciprofloxacin Hcl, so we will check the label claim of the suspension, which states that,
Each 5 ml of the suspension contains 125 mg of Ciprofloxacin
and the total volume of the single unit suspension is 60 ml.
Now we have the basic information, and by utilizing this information we will calculate the quantity of Ciprofloxacin Hcl required to manufacture 25000 units.
Before diving deep into this calculation, you must be familiar with the concept of factor value calculation for API which we discussed in the above mentioned article.
Factor Value Concept
For a brief overview, when the HCl is attached to ciprofloxacin, it is not required for pharmacological activity, but to enhance stability, solubility or penetration, so we have to adjust its value, which is known as the factor value.
For factor value calculation we use the following formula,
Molecular weight of API with salt÷Molecular weight of API without salt
For Ciprofloxacin
Molecular weight of Ciprofloxacin HCl ÷ Molecular weight of Ciprofloxacin
Put the values to calculate factor,
377.8÷331.34 = 1.11
1.11 is the factor value for Ciprofloxacin Hcl.
Calculation As Per Label Claim
Now we will calculate the API as per label claim which is 125 mg per 5ml.
The volume of suspension after reconstitution is 60 ml so first of all we will calculate the quantity of Ciprofloxacin Hcl for one bottle of suspension by following method
- 5 ml of suspension contains= 125 mg
- 1 ml of suspension contains =125/5
- 60 ml of suspension contains 125/5×60 = 1500 mg
The above calculation is for the situation where ciprofloxacin is used without salt, but in our case it contains HCl so we will adjust the factor value by multiplying the factor with our answer.
The factor value calculated above was 1.11 and our answer for 60 ml is 1500 mg so
- 1500×1.11 = 1665 mg
Mean 1665 mg of ciprofloxacin HCl will be equivalent to 1500 mg of ciprofloxacin.
API Calculation For Whole Batch
In the above, we have calculated the quantity of ciprofloxacin HCl required for one bottle of suspension, and now we can easily calculate the quantity of ciprofloxacin HCl required to manufacture a specific batch size, which in our case is 25000 bottles.
Use the following unit rule formula
- Ciprofloxacin HCl required for one suspension bottle 1665 mg
- Ciprofloxacin HCl required for 25000 suspension bottles= 1665 × 25000 = 41,625,000 mg
Now we will first convert this amount in grams by dividing it by 1000 and the answer will be as
41,625,000÷1000 = 41,625 gm.
Now convert grams into kilograms
41,625 ÷ 1000 = 41.625 kg
So the answer will be 41.625 kg
Label claim 2
Suppose we want to prepare a higher strength of ciprofloxacin HCl where the label claim states that 250 mg per 5ml and the total suspension volume after reconstitution is 60 ml.
So we will directly calculate the quantity of API and you can cross check it using the above step by step method.
The quantity of API will be 83.25 kilograms for the same batch size, i.e 25000 packs.
Conclusion
41.625 kg of Ciprofloxacin HCl for 125 mg potency will be required to fill 25000 bottles with 60 ml volume & 83.25 kg of Ciprofloxacin HCl will be required to fill 25000 bottles for 250 mg potency with final volume 60 ml per bottle.
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