Some / most ED drugs have a coating so they pass thorugh the stomach first, as the acid attacks the drug.

This can affect how pill splitting may be less effective. 1.4 of a 100 mg viagra may only deliver the equivalent of 1/8 of a pill. Perhaps internally to the pill the drug is micro-encapsulated, much like time release ADHD drugs are.

DMSO is a compound that is readily absorbed by the skin. It also has strong solvent properties for organics. Sildenafil has a solubility of 14 mg/ml in DMSO. So 25 ml would disolve in 2 ml of dmso.

DMSO is available in gel form at vet supply stores, as it's used a lot with horses.

So: Experiment idea:

Take a 100 mg viagra, grind to fine powder. Mix with 10 ml of DMSO gel. Let sit, mixing frequently. (Due to slow transport, the gel next to a particle saturates. Mixing is required to give fresh solvent a chance.

Apply the dmso either directly to penis, or as a body rub. Having your partner do the application may be stimulating itself.