Is there any medicine that prevent alzheimer patient from frequent walking and roaming ?

Yes but: I have no idea of what kind of meds are in egypt. There is little to do to actually prevent them from pacing. This is part of the disease pattern as the person can become restless. One can use benzodiazepines or haloperidol. There are other meds that may be used as well under the supervision of a doctor. Best wishes in this very difficult case

Couple choices: Rivastigmine and Namenda (memantine) may help agitation, but might also consider Seroquel or Risperdal. A local neurologist could help institute these drugs. Other choices may be considered.