Yes... I worked in the field of Addiction for several years.
It entirely depends on the meds he was on, what the dosage was and for how long. For some, detoxing is lethal (seizures, stroke, heart attack, death)... for others merely VERY dangerous (seizures, brain injury, homicidal rage, or suicidal depression)... for others merely VASTLY unpleasant (simultaneous vomiting and diarrhea, inability to stay still, panic/fear, insomnia, hallucinations, rage -but not homicidal-, depression -but not suicidal-, agitation, blinding headaches, irrational behavior, and sometimes up to several days/weeks of sleep). For each detox EXPECT all the vast unpleasantness... but you're very very lucky if that's all you get.
For MOST detox patients the first 72 hours are the worst... for medical detox patients these are the ones where they're in restraints to keep them from killing themselves or someone else, and have to be on certain types of meds to prevent seizures/ aneurysms/ death. For merely medically supervised detox (aka the danger group... but not the lethal group) the first 72 hours are also the worst... but they usually either aren't in restraints or are only in them the first 24-36 hours.
For non-medical detox (aka no risk of death, just vastly unpleasant), guess what? The first 72 hours are also the worst.
AFTER the 1st 72hours... you're looking at approximately a month of hell (one reason why inpatient treatment tends to be about a month long). Then after that first month of acute withdrawal, you will have PAWS (Post-Acute- Withdrawal-Symptoms... which is otherwise known as the mental and emotional rollercoaster, as a persons brain chemistry BEGINS to return to normal, with a few physical side effects thrown in for fun... but mostly mental and emotional) and then the next 2 years will be very VERY hard.
Rx drugs are frequently more addictive (harder to kick), and more dangerous than street drugs. Plus they're "sanctioned by society"... so they tend to be easier to get back on because the "stigma" isn't as attached to them as with street drugs.
Your mother may not need medical detox, but to find out PLEASE have her evaluated. Bring all of her prescriptions with you. Search out hiding places, and make a list of absolutely everything she has been on, & what the doses are. If possible, check with all the local pharmacies. Many Rx abusers have multiple doctors and multiple pharmacies... which is a series of felonies. Do, please, also look into residential treatment programs. Any good one will offer a free assessment (and from working in the field, I can tell you... NOT everyone is an addict, or addicted. They DO tell people when they think there isn't a problem, when the problem can be handled on an outpatient basis, and when they think a problem should be handled on an inpatient basis.
There also tend to be specific support groups set up for Rx abusers. Both through NA and through some treatment facilities.
Best of luck to you all,
R