Brief Answer:
Take lactulose 10-15 ml every night before going to bed.

Detailed Answer:
Hello Dear,
Thanks for query.

Constipation is very coomon among people who take Lithium carbonate, especially for people who are female, 50- 59 old , have been taking the drug for 2 - 5 years.
Suggestions-

For immediate relief take 10-15 ml of lactulose(Looz) stat followed by 10 ml in half cup of water everynight before you go to bed.Lactulose is a laxative and would help you to get relief from constipation and it has no effect on timnitus. Tinnitus is most likely also due to lithium.

Other things that will help in long term are-

-Take two tea spoon (or one big spoon) isphagula husk with 200 to 300 mL water this is a natural fiber would absorb water swell up and cause stools.
- increase warm water( atleast 8 glass/day) intake
- do not drink water during and after meals
- eat small meals (rich in fiber)
- eat plentiful "fresh oranges" and "pear "
- avoid cold milk and and junk foods.
- mix few drops of "lemon juice" in warm water. Drink on empty stomach, early in the morning, to aid in bowel movement
- avoid beverages / alcohol/ soft drinks
- do some exercise (push-ups / squats etc) early in the morning
- avoid carbonated drinks
- take 2-3 spoon edible virgin olive oil in the morning

Feel free to ask further
Regards

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