Do lactitol monohydrate and ispaghula husk granules have any side effects like lowering blood-pressure level or dehydrating the consumer?...

Yes, from diarrhea: Both lactitol & ispaghula (psyllium) can be used to treat constipation.Side effect can be diarrhea; if too much fluid is lost, blood pressure can drop& this much dehydration is dangerous.Symptoms include lightheadedness when standing.If unable to keep down enough liquids to compensate, get seen ASAP. Lactitol is much more likely to cause diarrhea (psyllium can used to treat some kinds of diarrhea)