Hello from JustAnswer.
Yes, it is usually OK to take another pill 2 hours later, as long as it is done cautiously. The recommended starting dose is one pill every 6 hours, and then the dose can be adjusted gradually up to a maximum dose of 12 pills per day. At the maximum dose, the medicine would be taken one pill every 2 hours or 2 pills every 4 hours.
However, it is recommended that the dose be adjusted gradually while monitoring for side effects, particularly signs of excessive sedation. The elderly are more prone to developing sedation and other side effects from medicines, so it would be important to avoid a second dose if there is still any sedation from the first dose. However, if the dose is adjusted gradually and the patient does not develop any side effects, it would be OK to take the pill at this dose.
If there has not been a gradual dose adjustment, it would still usually be OK to take a second dose at 2 hours as a one time dose, as long as there is no residual sedation from the first dose, and then the patient waits the full 6 hour period before taking another dose.
If I can provide any clarification, please let me know.