Switching from oral to topical Minoxidil?

I’m a post menopausal woman who experienced significant hair thinning/shedding for ~3 yrs. A dermatologist prescribed oral Minoxidil 2.5mg and, after the initial 4 wks of shedding, I’ve had terrific results. There is a shortage of the drug due to manufacturing disruption and I’m left with using Rogaine 5% foam. Am I likely to experience the shedding I had in the first 2-6 wks of taking oral Minoxidil? How about when I switch back to the oral? I don’t want to loose all the gains I’ve made! Thx!