They would love to deliver it the way that is most likely to be done correctly and most welcomed by the patients and doctors. That’s oral pills. They’ve come up with clever ways to do slow release that is protected from the stomach but absorbed in the intestines, for some drugs. Then it has to be protected from degrading enzymes so it stays in the blood or liver at the right level the longest before another pill is needed. Then the degradation products have to be harmless.

When a drug can’t be designed for this, you end up with things like multiple pills per day, or injections, or liquids, or patches, or nasal sprays, or rectal suppositories. Sometimes a patch is best because it can be slow release.