Rectal Drug Delivery


Integral BioSystems scientists have expertise in the design and implementation of drops, gel and sustained release systems to deliver both small molecule- and biologics into the rectal lumen. Contact us for a discussion on your API. 

In developing a drug formulation for the rectal route, the location of the target receptors (surface or intracellular), characteristics of the therapeutic (pka, log P, stability at alkaline pH (7.4-7.8), solubility, molecular weight, charge), ability to formulate the therapeutic in the usual rectal delivery modalities are factors in the drug development process.

Other factors to consider are the need to extend the residence time of the therapeutic, or ways to enhance the bioavailability of the administered drug, particularly if the drug is hydrophilic. The absorption surface of the rectum ranges between 0.02 and 0.05m2. A viscous rectal fluid is spread over the surface as the rectal mucosa, with very low buffer capacity. Thus, the carrier for a rectal drug product must be miscible with the rectal mucosa, and permeate the mucosa to reach the target receptors.

Additionally, the carrier must be compatible with the drug and preferably last in the tissue space as long as possible. For hydrophilic and labile actives, a suppository dosage form is unlikely. This is because the formulation process for suppositories involves high temperatures to melt the waxes for drug incorporation.


For a hydrophilic small molecule or biological drug, a chemically compatible, hydrophilic, mucous-adhesive drug delivery carrier is envisioned. The drug product can be delivered as a 2-5 mL fluid to achieve full coverage of the rectal space. The drug will be formulated in an aqueous solution of a bioadhesive polymer. The polymers are highly bioadhesive, thus enhancing their residence time. Another possibility is a uni-dose rectal gel, preloaded into a syringe for ease of delivery. 

Depending on the stability of the drug, storage conditions will be either refrigerated or RT. Both the enema and the rectal gel should be developed; the final formulation should be selected based on pharmacokinetics, drug product stability, ease of use and marketing considerations. A rectal gel clearly would have a higher patient compliance than an enema, if dose administration is frequent. 

CRO Services for Rectal Drug Delivery

Integral BioSystems is a contract research organization that provides quality services specializing in pre-clinical stage pharmaceutical research and development at a competitive price and turnaround time. Learn more about our CRO services > 

Ready to revolutionize rectal drug delivery with tailored formulations designed for optimal efficacy and patient compliance? Contact Integral BioSystems today to develop a customized solution that meets the unique needs of your API. Take the next step towards advancing rectal drug delivery with Integral BioSystems as your trusted partner!