A Diet for Constipation on Clozapine

How to protect your gut when clozapine causes constipation

Some medications slow your gut down, particularly clozapine. When that happens, food can get stuck — and that can turn into a serious emergency called a small bowel obstruction. If food can’t pass through, your intestines can burst. That’s why knowing the warning signs, and taking steps to prevent it, matters so much.

Warning Signs You Should Never Ignore

Call your doctor, NP, PA, or primary care provider if you notice any of these:

• No bowel movement in 2–3 days
• Unable to pass gas
• Severe, crampy stomach pain that comes in waves
• A swollen or bloated belly
• Persistent nausea or vomiting
• Bloody diarrhea

Which Medications Raise Your Risk?

The risk is highest with clozapine, especially when it’s taken with other meds that slow the gut, like:

• GLP-1 agonists: Semaglutide (Ozempic, Wegovy, Rybelsus), liraglutide (Victoza, Saxenda), dulaglutide (Trulicity)
• Opioids: Oxycodone, fentanyl, hydrocodone, codeine, buprenorphine, Suboxone, tramadol, and others
• NSAID pain relievers: Ibuprofen (Advil, Motrin), naproxen (Aleve), celecoxib (Celebrex), diclofenac (Voltaren), meloxicam (Mobic)
• Anticholinergics: Cyclobenzaprine, hydroxyzine, promethazine, oxybutynin, paroxetine, and others
• Tricyclic antidepressants: Especially amitriptyline, clomipramine, doxepin, and trimipramine
• Antipsychotics: Especially clozapine, olanzapine, quetiapine, chlorpromazine, and thioridazine
• Calcium channel blockers: Verapamil, diltiazem, nimodipine
• Parkinsonian medications: Benztropine, diphenhydramine, trihexyphenidyl
• Meds for overactive bladder: Oxybutynin, tolterodine, trospium, darifenacin, solifenacin
• Iron

Older adults are at higher risk, and people who have a narrowed section of the bowel (called a stricture) or a bowel tumor.

A Diet That Can Help

Clinicians in Australia developed this diet specifically to prevent bowel obstruction. It works by limiting foods that can clog your bowels and cause a dangerous blockage. The key reducing foods that don’t dissolve easily, starting with insoluble fiber.

What Is Fiber, Exactly?

Fiber is the part of a plant your body can’t digest. It travels through your bowels mostly intact, adding bulk to your stool. It also acts like a sponge, absorbing fluid and keeping your stool soft.

There are two kinds of fiber:

• Soluble fiber dissolves in water. It forms a thick gel in your bowels, which softens your stool and helps it pass more easily.
• Insoluble fiber does not dissolve in water. You find it in the rough, hard parts of plants — things like skins, grains, and seeds. It adds bulk to your stool, which sounds helpful, but for people at risk of obstruction, that extra bulk can cause a dangerous blockage in a narrowed part of the bowel.

Why You Need to Modify Your Fiber Intake

For most people, a high-fiber diet keeps the bowels healthy. But here’s the catch — if you have a narrowed area in your bowel, all that bulk from insoluble fiber can pile up and cause a blockage. Reducing the amount of insoluble fiber you eat lowers the risk of that happening.

Foods High in Insoluble Fiber to Watch Out For

These foods are the biggest sources of insoluble fiber. You don’t have to avoid all of them entirely, but you do need to prepare them carefully (more on that below):

• Fruit — especially the skin and seeds
• Vegetables — especially the skin and seeds
• Whole-grain products: breads, pasta, brown rice, quinoa
• Nuts and seeds
• Wheat and rice bran

Safe Foods with Soluble Fiber

• Some fruits: Apples, bananas, citrus fruits, bananas, apricots, and peaches
• Oats: oat bran, oatmeal, and barley
• Beans: including lentils, chickpeas, peas, and all beans
• Vegetables: Okra, eggplant, Brussels sprouts, sweet potatoes, carrots, broccoli, and beets

(Avocados are high in both soluble and insoluble fiber)

How to Cut Down on Insoluble Fiber

Small changes in how you prep and cook your food make a big difference. Here’s what to do:

• Peel everything. Remove the stalks, stems, pips, seeds, and skins from all fruits and vegetables.
• Cook your vegetables well. Soft, well-cooked vegetables are much easier to digest than raw ones.
• Chop tough, fibrous foods finely. Things like celery and mango have tough fibers — cut them into tiny pieces.
• Skip dried fruits, nuts, and seeds. These are concentrated sources of insoluble fiber.
• Strain your juices and soups. Run them through a strainer to remove fibrous bits.
• Switch to white. Avoid whole-grain, high-fiber breads and cereals. Choose white bread, white pasta, and white rice instead.

How to Prevent Constipation While Following This Diet

Cutting back on fiber can sometimes lead to constipation, but you can prevent that too:

• Drink plenty of water. Most people need 8–10 glasses of fluids every day. Water keeps things moving.
• Eat low-to-moderate fiber fruits and vegetables — just make sure you’ve removed all the skins, seeds, and stems first.
• Choose pureed or soft, well-cooked fruits and vegetables over raw ones when you can. They’re gentler on your gut.
• Talk to your doctor if constipation becomes a problem despite these changes.

General Tips for Everyday Eating

These habits will help you stay comfortable and reduce your risk:

• Follow a low-fiber diet, with a special focus on keeping insoluble fiber low.
• Chew every bite thoroughly before swallowing.
• Eat slowly in a calm, relaxed setting — rushing your meals stresses your digestive system.
• Cook your food well. Heat breaks down tough fibers and makes food easier to digest.
• Avoid anything tough or stringy — gristly meat is a good example of what to skip.
• Some people do best on soft or pureed foods to keep symptoms under control.
• Read food labels. If a product says it’s high in fiber, put it back.
• Eat 6–8 small meals throughout the day instead of 3 large ones. Smaller portions are easier for your gut to handle.
• Eat a variety of foods from all five food groups, choosing options that fit the guidelines in this post.

The Bottom Line

Protecting yourself from a bowel obstruction comes down to a few key habits:

• Modify your fiber intake — especially insoluble fiber — to reduce your risk.
• Peel your fruits and vegetables, and remove all stalks, stems, seeds, and pips.
• Cook and chew your food well.
• Drink plenty of water every day.
• Contact your primary care provider right away if you notice symptoms of a bowel obstruction.

	Food Group	No limits	Enjoy in moderation (suggested daily amounts)	Limit
Bread, cereals, rice, pasta, noodles	• White bread, muffins, non-whole grain English muffins • White pita bread • Refined breakfast cereals, eg Rice Krispies, Cornflakes • White rice, pasta, sago, tapioca, semolina • White flour, cornflour • Plain cookies and cakes • Crackers that are not whole grain, high fiber, or have seeds • Rice cakes	• Oats/oatmeal, instant, cooked (½ cup) • Fiber bars (½ bar) • Barley, cooked (¼ cup) • Chia seeds (1 teaspoon) • Sourdough bread (2 slices) • Light rye bread (1 thin slice)	• Anything made with seeds, nuts, dried fruit, or coconut, including cereals, bread, and sweets • Wholegrain bread, cereals, or crackers • Oat bran that is unprocessed, raw • Wild rice, brown rice, brown pasta
Dairy	• All types of milk • Plain yogurt, custard, plain cheese, ice cream	• Desserts with peeled and stewed fruit • Nutritional supplements with fibers	• Desserts with dried fruit, chunky fruit pieces, nuts, seeds or coconut • Smoothies made with whole fruits, seeds and high fiber cereals
Meat, fish, poultry, eggs, nuts, beans	• Any tender, soft meat, chicken or fish • Tofu • Eggs and soy products	• Smooth nut butters (1 tablespoon) • Beans: baked beans, kidney beans (2 tablespoons)	• Nuts & seeds • Crunchy nuts or seed butters (e.g. peanut butter, tahini)
Vegetables   Aim for vegetables that are peeled and well-cooked	• Potatoes • Pumpkin • Zucchini • Cauliflower and broccoli florets • Mushrooms   For salads: • Tomato and cucumber with skins and seeds removed • Iceberg lettuce (1 cup) • Capsicum (1 cup) cooked • Well strained vegetable juice • Tomato puree or paste	• Eggplant (1 cup) • Sweet potato, no skin (¼ cup) • Carrot, peeled (¼ cup) • Turnip, cooked (½ cup) • Onion, cooked (½ cup) • Okra, cooked (½ cup) • Silverbeet (½ cup) • Spinach (¼ cup) • Canned diced tomato (½ can)	• Vegetables that don’t have seeds/skins removed • Stringy vegetables (e.g. celery, broccoli stems, bean sprouts, asparagus) • Vegetables with tough skins (e.g. peas, corn) • Avoid all other vegetables not listed in foods to include.
Fruit	• Melons (no seeds) • Well-cooked fruit no skin/seeds • Canned fruits except pineapple • Fruit juice – no pulp	• Banana (1 small) • Apple, no skin (1 small) • Cherries/seedless grapes (1 cup) • Oranges, seeds removed (1 small) • Mango & papaya (2/3 cup) • Grapefruit (1 small) • Peeled peaches & nectarine, plum (1 medium) • Blueberries (½ cup)	• Fruit with skin, seeds or a very fibrous texture, eg pears, pineapple • Dried fruit • Fruit with small seeds (e.g. kiwi fruit, figs, dates, pomegranate) • Strawberries, raspberries, blackberries • Juice with pulp
Other	• All fats including butter, margarine, mayonnaise, oils • Sugar, honey, syrups • Candy with no fruit, nuts, seeds, or coconut • Spreads without seeds or skin • Broths/soup made from allowed ingredients • Desserts made from allowed foods (jelly, ice-cream, custard) • Gravy, salt, pepper, dried herbs & spices	• Chutney and pickles	• Popcorn • Coconut • Chocolate with nuts and fruit • Jams or pastes with nuts and seeds

—Chris Aiken, MD
Director, Psych Partners
Editor in Chief, Carlat Psychiatry Report