No volume effect on retrograde colonic spread of rectally-administered ropivacaine gel

Development and characterization of a novel mucoadhesive sol-gel suppository of sumatriptan: design, optimization, in vitro and ex vivo evaluation for rectal drug delivery

Aim: Sumatriptan (ST) is used for the treatment of migraine and cluster headaches. However, it exhibits low oral bioavailability (15%) due to the high first-pass metabolism. The aim of this work was to formulate an ST rectal hydrogel. Methods: Hydrogels were formulated according to a Box-Behnken design using pluronic F-127 (PF-127) and chitosan as thermogelling and mucoadhesive agents, respectively. The rectal permeability was examined using a sheep rectal mucosa. Results: Among all the formulations, the hydrogel S2 showed satisfactory drug content (4.50%), gelling temperature (32°C), pH (6.41), viscosity (105 cP) and strength (15.90 sec). Mucoadhesive strength was adequate to provide a prolonged residence time. The flux of hydrogel S2 was calculated to be 0.0003 μg/cm².min. Conclusion: The ST hydrogel can provide a potential opportunity to overcome the first pass metabolism and reduce drug dose.

A Comparative Pre-Phase I Study of the Impact of Gel Vehicle Volume on Distal Colon Distribution, User Experience, and Acceptability

For persons at risk of HIV infection who practice receptive anal intercourse (RAI), topical rectal microbicides represent a promising option for coitally dependent protection. The study compared colorectal distribution and user sensory experiences of two different volumes of rectal gel for suitability as rectal microbicide. Eight HIV-negative men with a history of recent RAI were enrolled into a two-period, sequence-randomized dosing study comparing 3.5 and 10 ml of radiolabeled (1 mCi ^99mTc-DTPA) universal placebo, hydroxyethyl cellulose gel. Each participant received two doses in the research unit, one of each volume, separated by a washout period of at least 2 weeks. Each research unit dose was followed by a self-administered take-home dose in the context of preparing for RAI. Safety and gastrointestinal distribution were assessed after the research unit doses, safety, perceptibility, and acceptability, were assessed after take-home doses. There were no adverse effects of Grade 2 or higher and all resolved spontaneously. Both volumes were well tolerated and received high acceptability scores. Perceptibility scores showed meaningful effect size differences ranging from Cohen's d = 0.5 to d = 1.2. The 3.5 and 10 ml gel volumes distributed similarly (p > .2) within the rectosigmoid, ranging from 0.69 to 18.84 cm and 1.21 to 19.01 cm from the anorectal junction, respectively. Both volumes covered the typical gastrointestinal distribution of ejaculate following simulated intercourse based on other studies. Either of these gel volumes could reasonably be pursued for the next phase of development of rectal microbicides.

Distribution of cell-free and cell-associated HIV surrogates in the colon after simulated receptive anal intercourse in men who have sex with men

OBJECTIVES

Describing the distribution and clearance of HIV surrogates within the gastrointestinal tract to inform rectal microbicide development.

DESIGN

Radiolabeled simulated HIV-infected semen was administered, imaged, and biopsied to simulate and measure colonic HIV distribution after anal intercourse.

METHODS

Healthy male subjects with a history of receptive anal intercourse and experience with the use of anal sex toys were recruited to this study. Apheresis isolated leukocytes were collected before simulated intercourse. These autologous leukocytes, radiolabeled with 9.25 MBq (111)Indium-oxine (cell-associated HIV surrogate), and sulfur colloid particles, labeled with 37 MBq (99m)Technectium (cell-free HIV surrogate), were mixed in 3 mL autologous seminal plasma. This simulated HIV-infected semen was administered to subjects via an artificial phallus with urethra after 5 minutes of simulated intercourse. Postdosing dual isotope Single photon emission computed tomography coupled with traditional computed tomography (SPECT/CT) images were acquired at 1, 4, 8, and 24 hours. At 5 hours postdosing, colon biopsies were collected, CD4 cells were extracted, and samples analyzed for radioactivity.

RESULTS

SPECT/CT images showed similar luminal distribution for both surrogates, with migration limited to the rectosigmoid colon in all subjects. SPECT showed at least 75% overlap in distribution of both surrogates up to 4 hours after dosing. Biopsies indicate that 2.4% of CD4 cells extracted from rectosigmoid colon tissue were exogenously administered.

CONCLUSIONS

Our HIV surrogates stayed within the rectosigmoid colon for 24 hours. Exogenously dosed autologous lymphocytes and HIV-sized particles migrate to similar locations and associate with the colonic tissue in the lumen.