The Pharmaceutics and Compounding Laboratory
Gels
 

Laboratory Procedure

The suitability of a 0.5% and 1.0% methylcellulose 1500 gel as a tablet vehicle will be determined. Work with a partner and one of you make a 0.5% MC 1500 gel with enalapril tablets, and the other make a 1.0% MC 1500 gel with enalapril tablets. Controls (i.e., 0% methylcellulose) will be provided for the lab. You will use the controls in a comparison with the gels you made. The procedure given in the “Method of Preparation” below is for one formulation. Therefore, you will use the same procedure twice, only varying the percentage of MC 1500 used.

On the following day, return to the lab and compare various parameters between the two gels you and your partner made, and the control provided. A chart has been provided under the “Quality Control Procedures” section for your use in evaluating the different gels. There are also “Questions to Answer” for you and your partner to complete. 

Ingredient

Quantity

Physical Description

Solubility

Therapeutic Activity

Enalapril Maleate Tablets, USP

10 tablets

Round, white, scored tablets

enalapril: 0.025 g/ml in water; 0.08 g/ml in alcohol; 0.20 g/ml in methanol

ACE inhibitor

Methylcellulose 1500 USP

see below

White to yellowish-white granules or free-flowing powder, odorless, tasteless

swells and disperses slowly in water; insoluble in ethanol and hot water

suspending agent

Purified Water

qs 100 ml

clear, colorless liquid, low viscosity

N/A

vehicle

Equipment Required:

  • mortar and pestle
  • prescription balance
  • 150 ml beaker
  • 100 ml graduated cylinder

Method of Preparation:

  1. Obtain enalapril tablets from a stock bottle.
  2. Triturate the tablets in a mortar with a pestle.
  3. Calibrate a 150 ml beaker to 100 ml, and add water to about 90% of the calibration mark.
  4. Add the tablet mixture to the water with modest stirring.
  5. Accurately weigh the methylcellulose (amount will depend on final concentration).
  6. With vigorous stirring, add the methylcellulose to the water through a 40 mesh sieve.  Be careful to avoid forming powder clumps.  Remove stirring bar when the gel forms and complete stirring with a stirring rod.
  7. When all the methylcellulose powder has been added to the water, qs with water to the calibrate mark, and transfer to a 100 ml graduated cylinder. Do not qs in the cylinder.

Description of Finished Product:

The MC 1500 gels with enalapril tablets will be gray, opaque gels of medium to high viscosity.  Upon settling, the liquid phase may clear.

 

Quality Control Procedures: (1 day later)

Student Names: ______________________    _____________________   TA: _________________________

Formulation

Liquid Phase Clarity (describe)

Sedimentation Volume (*)

Redisperse to Uniform Product (# of inversions)

Particle Size

(**)

0% MC 1500 (control)

       

0.5% MC 1500

       

1.0% MC 1500

       

    * Scale for sedimentation volume:
      no sedimentation; visible, but not measurable;visible, and approximately _____ ml.

    ** Compare particle size to that of control. Is it the same size? If different, describe the difference.

 

Questions to Answer.

1.  When and why would you use a 0.5% methylcellulose gel compared to a 1.0% gel in practice?

 

 

2.  What is one practical limitation of using a methylcellulose gel as a delivery vehicle for tablets?

 

 

3.  What does the 0.5% MC 1500 gel taste like (put just a drop on your finger). What about the 1.0% MC 1500? Would you think that the taste of the formulation would be a limit to its use?

 

 

4.  Did it appear that all of the MC 1500 (either concentration) had hydrated when you returned to lab the following day?

 

 

5.  Remember the Lidocaine gel you made? That used Carbopol, an alcohol soluble gel. Methylcellulose is a water soluble gel. Compare the hydration rates of the two gels. Which seemed faster or easier?