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The RWD Osmotic Pump is a small, long-term, continuous drug delivery device that can be used in a wide range of applications. An osmotic pump is implanted subcutaneously or intraperitoneally and can be used for systemic administration, drugs can also be delivered to specific sites such as intravenous, intracranial, and distant local tissues by connecting catheters. This technology offers the possibility of drug delivery in many fields, such as cancer, neuroscience, gene therapy, cardiovascular, endocrine, pharmacology, toxicology, physiology, immunology, and other research fields.
This article provides a detailed summary of common problems when using osmotic pumps, including how they work, product information, and precautions when operating them. Having a comprehensive understanding of this information will help improve the success rate of your experiment.
The osmotic pump can be embedded in the subcutaneous or intraperitoneally of the animal, the outermost layer of the pump is pellicle, and the middle layer is a salt interlayer, due to the osmotic pressure, the animal tissue fluid enters the salt interlayer in one direction, and the pressure gradually increases after the salt interlayer absorbs the tissue fluid, so as to squeeze the internal compressible storage capsules, and finally pump out the drug solution in the storage at a known and controllable rate.
No, because the compressed storage capsules cannot be restored and refilled, the osmotic pump can only be used once and cannot be reused.
The osmotic pump absorbs animal tissue fluid through the saline interlayer with high permeability, which generates pressure inside the pump to pump out the drug solution. Incubation is to allow the saline interlayer to fully absorb 0.9% medical saline at 37°C in advance, ensuring stable pressure inside the pump. This ensures that the drug solution can be pumped out at a stable and uniform rate when the infusion pump is implanted in the animal body.
Animal Weight: RWD pumps can be implanted subcutaneously or intraperitoneally according to the following list.
| model | 100μL | 200μL | 2mL | |
| mice | subcutaneous | ＞10g | ＞35g | n/a |
| Intraperitoneal | ＞20g | n/a | n/a | |
| rats | subcutaneous | ＞10g | ＞35g | ＞150g |
| Intraperitoneal | ＞20g | ＞150g | ＞300g | |
Route of administration: Implant an osmotic pump subcutaneously or intraperitoneally for systemic administration, and for targeted administration of intravenous, intracranial, and distant local tissues by connecting the catheter.
| Application scenarios | Model | Suitable for animals |
| systemic administration | RWD pump | Mice, rats, rabbits and other experimental animals |
| Intracranial administration | RWD pump+ Bic-3 （The depth of the target brain area is 1-3 mm） | Mice, rats, rabbits and other experimental animals |
| RWD pump+ Bic-5 （The depth of the target brain area is 3-5 mm） | Mice, rats, rabbits and other experimental animals | |
| Remote local tissue administration | RWD pump+ Mic | Mice, rats, rabbits and other experimental animals |
| Jugular vein administration/ Jugular artery administration | RWD 2ML osmotic pump + rat jugular vein/rat jugular artery catheter (PURJV/PURCA) | rats, rabbits and other experimental animals |
| Femoral vein/femoral artery | RWD 2ML osmotic pump + rat femoral vein/rat femoral artery catheter (PURFV/PURFA) | rats, rabbits and other experimental animals |
Dosing time: RWD osmotic pumps have a nominal continuous dosing time range of 3 days to 6 weeks, and if your study requires a longer dosing time, a longer duration can be achieved with serial implantation. For example, continuous dosing for 2 months can be achieved by implanting a 4-week pump, removing it after one month, and replacing it with a new 4-week pump. RWD osmotic pump product information is shown in the table below:
| Capsule | Capacity | 100μl | 200μl | 2mL | |||||||||
| Type | 1003D | 1001W | 1002W | 1004W | 1006W | 2003D | 2001W | 2002W | 2004W | 2mL1W | 2mL2W | 2mL4W | |
| Duration | 3D | 1W | 2W | 4W | 6W | 3D | 1W | 2W | 4W | 1W | 2W | 4W | |
| Pumping Rate(μL/hr) | 1 | 0.5 | 0.25 | 0.125 | 0.083 | 2 | 1 | 0.5 | 0.25 | 10 | 5 | 2.5 | |
| Flow regulator | Cap | Without | PE material | ||||||||||
| Tube | 304 stainless steel material | ||||||||||||
| Infusion | Syringe | Flat head for the injection of liquid | |||||||||||
Pumping rate: It is important to choose the appropriate pumping rate, e.g., for brain administration, a pump with a lower flow rate is usually preferred, and for poorly soluble compounds, a pump with a faster flow rate and a larger volume is required;
Drug properties:
a. Stability, osmotic pumps can be used for drugs that remain stable in matrix solutions at 37°C, or for suspensions (e.g., honey) with viscous solutions below 100,000 CP that do not precipitate.
b. Concentration, the formula (K=CQ) can be used to calculate the concentration of the liquid medicine injected into the osmotic pump.
Calculation of Drug Concentration: C=Kd/Qd, where C represents drug concentration (μg/μL); Kd represents daily dosage (μg/d); Qd represents daily dosage volume (μL/d).
c. Drug dose: Depending on the weight of the animal (e.g., adult rat or heavier), multiple pumps can be implanted at the same time to achieve continuous dosing of larger doses than a single pump.
RWD osmotic pump accessories need to be ordered separately, the accessories package and its purpose are shown in the following table:
| Application scenarios | Model | Suitable for animals |
| systemic administration | RWD pump | Mice, rats, rabbits and other experimental animals |
| Intracranial administration | RWD pump+ Bic-3 （The depth of the target brain area is 1-3 mm） | Mice, rats, rabbits and other experimental animals |
| RWD pump+ Bic-5 （The depth of the target brain area is 3-5 mm） | Mice, rats, rabbits and other experimental animals | |
| Remote local tissue administration | RWD pump+ Mic | Mice, rats, rabbits and other experimental animals |
| Jugular vein administration/ Jugular artery administration | RWD 2ML osmotic pump + rat jugular vein/rat jugular artery catheter (PURJV/PURCA) | rats, rabbits and other experimental animals |
| Femoral vein/femoral artery | RWD 2ML osmotic pump + rat femoral vein/rat femoral artery catheter (PURFV/PURFA) | rats, rabbits and other experimental animals |
One is the flow regulator with the white flange and one is the exposed flow regulator. For subcutaneous or intraperitoneal drug delivery scenarios, choose a flow regulator with a white flange; for scenarios where a catheter needs to be connected for drug delivery to special parts such as the brain and blood vessels, choose an exposed flow regulator, connect it to the catheter and embed it in the body.
No, the pumping rate is determined by the permeability of the pellicle of the pump body. Therefore, the pumping rate curve is independent of the type of chemical in the pump. Drugs in a variety of molecular configurations, including macromolecules and ionized drugs, can be pumped continuously at a controlled rate. The molecular weight of a compound or its physical and chemical properties are independent of the pumping rate.
