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Introduction Click Here to Find the Osmolarity of Selected Large and Small Parenterals for Your Protocol!
We, at the McGuff Company and McGuff Compounding Pharmacy, share your concern for patient safety and well being. The unique osmotic properties of large volume parenteral injections require a special awareness and understanding by the physician to assure patient safety. Traditionally, the calculation of osmotic pressures of Large and Small Volume Parenteral Injections has posed a problem for the office based physician. The average office based physician has limited access to diverse chemistry references and most importantly, limited time for performing the lengthy calculations necessary to achieve accurate osmotic pressure. This osmolarity table represents our efforts to reduce the time and effort necessary for the calculation of osmolarity in Large Volume Parenteral Injections. This table was produced through the combined efforts of our manufacturers, chemists, pharmaceutical laboratory and Compounding Pharmacy. By experience, the expected osmolarity derived from using this table correlates closely with actual osmolarity.1 It is however, important to test for actual osmolarity whenever possible. Isotonic solutions are those solutions which fall in the range of 280 to 310 milliosmoles per liter. Patient safety and comfort is best achieved by utilizing a solution which approximates this isotonic condition. Please note that all osmolarity computations used to produce this table are based on injections available from the McGuff Medical Products or Compounding Pharmacy. Injections from other sources may vary in osmotic pressures due to differences in manufacturer/compounder and manufacturing/compounding process and would, therefore, invalidate the use of this table. Please feel free to call your McGuff Company Customer Service Representative if you have any questions. Better yet, our customer service representatives are available to calculate expected osmolarities for you. Most osmolarity calculations can be done while you are on the telephone with a conformation copy of the results mailed to you the same day - free of charge! Additionally, we may be able to help with suggestions or recalculate osmolarity should there be a need. Our computer software program for the determination of EDTA dosage, estimated osmolarity and sodium content of IV solutions is available at nominal cost. This program is Microsoft Windows compliant. By having your own program you will be able to fine tune your protocol just the way you want to whenever you want to! We at the McGuff Company are proud that we are able to bring important, time saving information to you. Our customer service representatives and technical support personnel await any questions that you may have! |
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The method for estimating the osmolarity of an I.V. Solution follows: [1.] For each component of the mixture, including sterile water, multiply the volume in milliliters of that component times the table value of milliosmoles present of the component. [2.] Add the products obtained in step [1] for each of the components in order to determine the total number of milliosmoles in the mixture. [3.] Add together each of the volumes in order to obtain an estimate of the final total volume of the mixture. [4.] Divide the total number of milliosmoles from step [2] by the total volume from step [3], then multiply by 1,000 to obtain an estimate of the osmolarity of the mixture in units of milliosmoles per liter.2 (This value also approximates the osmolarity in units of milliosmoles per kilogram). |
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Example Calculation
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If the estimated osmolarity of the IV solution does not fall within the isotonic range, the following adjustments may be made. 1. If the calculated estimate of osmolarity is too low (less than 280mOsm/liter) the osmolarity may be raised by:
2. If the calculated estimate of osmolarity is too high (greater than 310mOsm/liter) the osmolarity may be lowered by:
3. Those components with high table values of milliosmoles present will require smaller additions or deductions than those with low table values. 4. Special consideration should be given to the consequences the adjustments may have on the intended results of therapy. |
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1. Isotonic: 1. Of equal tension. 2. Denoting a solution in which body cells can be bathed without net flow of water across the semipermeable cell membrane; also, denoting a solution having the same tonicity as another solution with which it is compared. 2. Osmolarity: the concentration of the solute in a solution per unit of solvent. 3. Solution: a homogeneous mixture of one or more substances (solutes) dispersed in a sufficient quantity of dissolving medium (solvent). |
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1. Actual Osmolarity tests of three unique large volume protocols were used to validate this method of determining estimated osmolarity. A comparison was made between the actual osmolarity of each protocol to its calculated osmolarity derived from this table. Calculated values were plus 3%, minus 2% and minus 13% of actual osmolarity. 2. All osmolarity computations are based on injections available from the McGuff Company or McGuff Compounding Pharmacy. Injections from other sources may vary in osmotic pressures due to differences in manufacturer and manufacturing process and would, therefore, invalidate the results of this table. 3. An expected osmotic pressure of a biological product. Actual range will vary from 0.38 to 0.46 milliosmoles. 4. WARNING: Sterile Water for Injection is Hypotonic and Hemolytic. Do not inject until made approximately isotonic by addition of appropriate solute. |
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McGuff Company |
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