Drug & supplement interaction

Chitosan + Alendronate

Alendronate brand names: Fosamax, Binosto.

No Known Interaction
Medically reviewed by · Updated July 2026 · Pair last verified Sep 13, 2026
The bottom line No known interaction

We found no known interaction between Chitosan and Alendronate in our sources. Absence of a documented interaction is not the same as proven safety, and does not guarantee one does not exist. Do not start, stop, or change a medication or supplement based on this page; confirm with your pharmacist or doctor first. Additionally, although there is no interaction, there is a timing consideration — Chitosan can reduce how much Alendronate you absorb if they are taken together, so they should be spaced apart, and the two are separately associated with some of the same side effects, which would make a new symptom harder to attribute to one or the other.

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Interaction report

Chitosan and Alendronate

We checked these two against our interaction database. Here is what we found.

No Known Interaction Found

We did not find a documented interaction between Alendronate and Chitosan in our sources. This does not guarantee that the combination is completely free of risk — there is often limited research on supplements and herbal products, especially around drug interactions.

If you decide to take both, the practical routine is simple: add one new thing at a time and note the date you started it. If the combination is going to disagree with you, it usually shows in the first days to a couple of weeks — and a start date turns “I’ve been feeling off” into something a pharmacist can actually work with. Do not stop a prescribed medicine on your own.

Always talk with your pharmacist or doctor before making changes to your medications or supplements, particularly if you take several medications or have an ongoing health condition.

Chitosan safety at a glance

Chitosan overall Use caution Generally well tolerated short-term, but quality evidence is limited and shellfish allergy is a concern.
Pregnancy Avoid Not enough safety data; avoid use during pregnancy.
Breastfeeding Avoid Not enough safety data; avoid use while breastfeeding.

Safety guidance is general; always confirm with your pharmacist or doctor for your situation.

Still wondering about combining Alendronate and Chitosan? Ask Dr. Brian Staiger, PharmD, BCPS directly ›
How we checked

Why No Interaction Is Listed for Alendronate

Interactions in our licensed database are recorded against drug classes, not just single drug names. Alendronate is filed under 3 classifications — including bisphosphonates, oral drugs. Chitosan has documented interactions with 2 drug classes — the most serious being acyclovir (zovirax) (moderate) and warfarin (coumadin) (moderate) — and none of Alendronate’s classifications are among them.

Classification data comes from our licensed Natural Medicines dataset. A medication can belong to classes beyond those recorded there, so this describes how the check was run — it is not a safety guarantee.

Keep it in perspective

Chitosan Does Interact With Other Medications

Chitosan has 3 moderate known drug interactions in our database — Alendronate isn’t one of them. If you take anything else, check it against the full list below.

Moderate 3 No known interaction 2,827 (incl. Alendronate)
Taking anything else?

Check Another of Your Medications Against Chitosan

Covers the 2,830 medications we’ve checked against Chitosan. Pick one to open its full report.

What to actually watch for

No Interaction Found — But Data Suggests Chitosan and Alendronate May Share Several of the Same Side Effects

This is not an interaction. Neither one changes how your body handles the other, and nothing here says they react together. What our sources do show is that each has separately been linked to the effects below — so taking both can make those effects more likely to turn up, and harder to pin on one or the other if they do.

  • Bloating or gas / Stomach upset / Constipation / Diarrhea / Nausea Additional detail

    Chitosan

    “Orally, chitosan has been reported to cause epigastric discomfort, constipation, flatulence, diarrhea, nausea, and dryness of the throat. Excessive discharge of fat in the feces, also known as steatorrhea, has been reported with chitosan therapy.”

    Chitosan · Natural Medicines adverse-effect record, reported in constipation.

    6 sources cited
    1. 1942. Jing SB, Li L, Ji D, et al. Effect of chitosan on renal function in patients with chronic renal failure. J Pharm Pharmacol 1997;49:721-3. PubMed
    2. 3243. Pittler MH, Abbot NC, Harkness EF, Ernst E. Randomized, double-blind trial of chitosan for body weight reduction. Eur J Clin Nutr 1999;53:379-81. PubMed
    3. 9986. Ho SC, Tai ES, Eng PH, et al. In the absence of dietary surveillance, chitosan does not reduce plasma lipids or obesity in hypercholesterolaemic obese Asian subjects. Singapore Med J 2001;42:6-10.
    4. 11307. Bokura H, Kobayashi S. Chitosan decreases total cholesterol in women: a randomized, double-blind, placebo-controlled trial. Eur J Clin Nutr 2003;57:721-5. PubMed
    5. 14314. Mhurchu CN, Poppitt SD, McGill AT, et al. The effect of the dietary supplement, Chitosan, on body weight: a randomised controlled trial in 250 overweight and obese adults. Int J Obes Relat Metab Disord 2004;28:1149-56. PubMed
    6. 41688. Wuolijoki, E., Hirvela, T., and Ylitalo, P. Decrease in serum LDL cholesterol with microcrystalline chitosan. Methods Find.Exp Clin Pharmacol. 1999;21(5):357-361. PubMed

    Alendronate

    Listed in the ADVERSE REACTIONS section of the FDA label for Alendronate. Read the label on DailyMed ›

  • Itching Additional detail

    Chitosan

    “In one clinical trial, a subject with kidney failure reported itching during 12 weeks of oral chitosan treatment. It is not clear if this was related to the underlying renal failure or the use of oral chitosan.”

    Chitosan · Natural Medicines adverse-effect record, reported in kidney failure.

    1 source cited
    1. 1942. Jing SB, Li L, Ji D, et al. Effect of chitosan on renal function in patients with chronic renal failure. J Pharm Pharmacol 1997;49:721-3. PubMed

    “Topically, an eye drop containing chitosan-N-acetylcysteine has been reported to cause itching and irritation of the eyes.”

    Chitosan · Natural Medicines adverse-effect record, reported in pruritus.

    1 source cited
    1. 97710. Schmidl D, Werkmeister R, Kaya S, et al. A Controlled, Randomized Double-Blind Study to Evaluate the Safety and Efficacy of Chitosan-N-Acetylcysteine for the Treatment of Dry Eye Syndrome. J Ocul Pharmacol Ther. 2017;33(5):375-382.

    Alendronate

    Listed in the ADVERSE REACTIONS section of the FDA label for Alendronate. Read the label on DailyMed ›

Reported for Chitosan but not commonly for Alendronate: kidney problems.

Effects for Alendronate come from the ADVERSE REACTIONS section of its FDA label; effects for Chitosan come from the Natural Medicines adverse-effect record, quoted above. Wording is matched across sources by our own clinical vocabulary, so treat this as a prompt to pay attention, not a diagnosis.

Timing matters

No Interaction — But Take Chitosan and Alendronate a Few Hours Apart

Alendronate is a bisphosphonate, and it is absorbed best on its own. Chitosan can bind to it in the stomach so that less of the medicine reaches your bloodstream. That is not an interaction in the usual sense — nothing harmful happens when they meet — but taken at the same time, your dose can effectively become a smaller one.

The fix is simple: separate the two by about 4 hours. Take Alendronate first, on its own, and keep Chitosan for later in the day.

Where this comes from: this is HelloPharmacist editorial guidance, not a licensed interaction record — it applies established absorption pharmacology to bisphosphonates, whose FDA labels state a separation requirement of their own. The Alendronate label is summarised on our Alendronate drug page, and the full label is on DailyMed. Reviewed by the HelloPharmacist pharmacy team. If you already take them together, do not change your medicine on your own; ask your pharmacist how to space them.

From our Q&A

Questions About Chitosan or Alendronate

These are real questions from readers, answered by the pharmacists at HelloPharmacist — written by a person, not generated from a database. Each one covers Chitosan or Alendronate, not necessarily both, but if one is close to what you were about to ask it will usually go further than a database entry can:

Not quite your question? Ask our pharmacists directly — it is free, there is no account required, and answers usually come back within 24 hours.

Everything else you take

See Every Supplement That Interacts With Alendronate

This page covers Chitosan only. If you take other supplements — a multivitamin, a sleep aid, something for joints — the Alendronate page lists 25 supplements it has a documented interaction with, worst first, each one explained.

The most serious there right now: Activated Charcoal (major), Calcium (moderate), Coffee (moderate), Coffee Charcoal (moderate) and Dolomite (moderate).

By severity: 1 major · 15 moderate · 9 minor.

From our pharmacist’s overview on the Alendronate page

“Picture the typical Fosamax (alendronate) patient: someone taking a weekly tablet for thinning bones who also takes calcium and other mineral supplements, exactly what fills this list. Nearly all 25 ingredients on file work the same way, binding the drug in the gut or coating it with fiber so less gets absorbed, and a dose that never r…”

Reviewed by 2 · Jul 18, 2026

Open the Alendronate interaction page

One more smart check

Taking Chitosan as Part of a Dietary Supplement Product? Check It for Interactions

We hold 167 real supplement products containing Chitosan, each one broken down to its full ingredient list — and combination products often carry several ingredients besides Chitosan. Even though Chitosan itself has no known interaction with Alendronate, another ingredient on your label might. Find your product and we’ll check every ingredient on its label:

How much people look this up

Where Chitosan and Alendronate Sit Against Everything Else

Out of every supplement and medication people look up on HelloPharmacist, here is where these two land this week — and which way each has been moving.

Supplement Chitosan
Steady interest

#910 of 1,452 supplements looked up here in the last 7 days

29 days ago today
Medication Alendronate
Top 10%

#260 of 2,830 medications looked up here in the last 7 days

29 days ago today

Position among everything looked up on this site, not a measure of how commonly either one is used or how important it is. A supplement can climb this list because of a news story. It counts every request to the page, automated ones included, and nothing here identifies anyone.

Where does our data come from?
  • Source: the Natural Medicines (TRC Healthcare) clinical database — the evidence-graded professional reference for herb & supplement interactions.
  • Citation library: 103,510 references behind our interaction content, 65,311 of them resolved to verified PubMed/DOI sources. See every Chitosan reference on this page ↓
  • Freshness: we automatically re-check this combination every week — this pair was last verified September 13, 2026. The Chitosan and Alendronate records this page draws on were last updated July 10, 2026.
  • What “no known interaction” means: no documented interaction in the sources above — not a guarantee of safety. Supplements are studied far less than prescription drugs, so we say exactly what the evidence supports, and nothing more.
Data structure & sourcing designed and verified by .
Supplement

About Chitosan

What is Chitosan?

Chitosan
  • Weight management
  • Lowering cholesterol
  • Wound care
  • General digestive supplement

Chitosan is a fiber-like substance made from the shells of shrimp, crabs, and other shellfish, often marketed for weight loss and cholesterol. The evidence for these benefits is weak, and any effects appear small at best. It is generally well tolerated for short-term use, but people with shellfish allergies and those who are pregnant or breastfeeding should be cautious.

Shells of crustaceans (the source of chitin, which is processed into chitosan) · Capsules, tablets, powder

An interaction check asks whether these two react with each other — it does not ask whether Chitosan is a good idea for someone in your situation. Here is what our Chitosan record says about it on its own.

Chitosan: dosing

There is no official standardized dose for chitosan, and amounts used in studies have varied widely. Because of this, it is best to follow the directions on the product label and not exceed them.Chitosan is often taken with meals and a full glass of water.

From our Chitosan monograph — the full record covers uses, side effects and every documented interaction.

Read the full Chitosan monograph & all interactions
Medication

About Alendronate

What Is Alendronate Used For?

Brand names: Fosamax, Binosto

Alendronate tablets (including Alendronate, Alendronate Sodium, and Fosamax) are used to treat and prevent osteoporosis in postmenopausal women, treat osteoporosis in men, treat glucocorticoid-induced osteoporosis (bone loss caused by long-term steroid use) in men and women, and treat Paget's disease of bone. Binosto effervescent tablet is specifically indicated for treating osteoporosis in postmenopausal women and increasing bone mass in men with osteoporosis.

Alendronate Sodium oral solution is indicated for treating osteoporosis in postmenopausal women and increasing bone mass in men with osteoporosis. Alendronate helps build bone mass and reduce the risk of fractures, including hip and spinal fractures.

See full Alendronate drug information
Keep checking

Other Drugs & Chitosan

Browse every other medication we’ve checked against Chitosan — both the ones with a known interaction and the ones without. Select any drug for the full detail.

0Major
3Moderate
0Minor
2,826No known interaction
3 Moderate 2,826 No interaction
Moderate

3 interactions

No interaction 2,826 drugs checked — show the list

We also checked Chitosan against these medications and found no known interaction in our sources. Open any page to confirm.

Showing the 60 most looked-up of 2,826 medications checked with no known interaction — see the full Chitosan list.

See the full Chitosan interactions page
See every supplement checked against Alendronate, ranked by severity
Evidence & sources

Chitosan References

The 17 references that drive our Chitosan monograph and interaction data, from the evidence-graded Natural Medicines (TRC Healthcare) database. Citations with a link open the study on PubMed or the publisher’s site.

  1. Jing SB, Li L, Ji D, et al. Effect of chitosan on renal function in patients with chronic renal failure. J Pharm Pharmacol 1997;49:721-3. PubMed
  2. Pittler MH, Abbot NC, Harkness EF, Ernst E. Randomized, double-blind trial of chitosan for body weight reduction. Eur J Clin Nutr 1999;53:379-81. PubMed
  3. Ho SC, Tai ES, Eng PH, et al. In the absence of dietary surveillance, chitosan does not reduce plasma lipids or obesity in hypercholesterolaemic obese Asian subjects. Singapore Med J 2001;42:6-10.
  4. Bokura H, Kobayashi S. Chitosan decreases total cholesterol in women: a randomized, double-blind, placebo-controlled trial. Eur J Clin Nutr 2003;57:721-5. PubMed
  5. Mhurchu CN, Poppitt SD, McGill AT, et al. The effect of the dietary supplement, Chitosan, on body weight: a randomised controlled trial in 250 overweight and obese adults. Int J Obes Relat Metab Disord 2004;28:1149-56. PubMed
  6. Huang SS, Sung SH, Chiang CE. Chitosan potentiation of warfarin effect. Ann Pharmacother 2007;41:1912-4. PubMed
  7. Tsai, G. J. and Su, W. H. Antibacterial activity of shrimp chitosan against Escherichia coli. J Food Prot. 1999;62(3):239-243. PubMed
  8. Wuolijoki, E., Hirvela, T., and Ylitalo, P. Decrease in serum LDL cholesterol with microcrystalline chitosan. Methods Find.Exp Clin Pharmacol. 1999;21(5):357-361. PubMed
  9. Nelson, J. L., Alexander, J. W., Gianotti, L., Chalk, C. L., and Pyles, T. Influence of dietary fiber on microbial growth in vitro and bacterial translocation after burn injury in mice. Nutrition 1994;10(1):32-36.
  10. Schiller RN, Barrager E, Schauss EA, and et al. A randomized, double-blind, placebo-controlled study examining the effects of a rapidly soluble chitosan dietary supplement on weight loss and body composition in overweight and mildly obese individuals. J
  11. Koide, S. S. Chitin-chitosan: properties, benefits and risks. Nutrition Research 1998;8(6):1091-1101. DOI
  12. Maezaki Y, Tsuji K, Nakawa, and et al. Hypocholesterolaemic effect of chitosan in adult males. Biosc Biochem Biotech 1993;57:1439-1444.
  13. Kubbinga M, Nguyen MA, Staubach P, et al. The influence of chitosan on the oral bioavailability of acyclovir-a comparative bioavailability study in humans. Pharm Res 2015;32(7):2241-9. PubMed
  14. Jull AB, Ni Mhurchu C, Bennett DA, et al. Chitosan for overweight or obesity. Cochrane Database Syst Rev 2008;(3):CD003892. PubMed
  15. Schmidl D, Werkmeister R, Kaya S, et al. A Controlled, Randomized Double-Blind Study to Evaluate the Safety and Efficacy of Chitosan-N-Acetylcysteine for the Treatment of Dry Eye Syndrome. J Ocul Pharmacol Ther. 2017;33(5):375-382.

Medication overviews come from MedlinePlus (NIH); supplement label data from the NIH Dietary Supplement Label Database. Content is written and reviewed by licensed HelloPharmacist pharmacists — see our data sources and editorial standards.

Pharmacist Counseling Corner

Taking Chitosan and Alendronate Together: Common Questions

Is it safe to take Chitosan with Alendronate?
We do not list a known interaction between Chitosan and Alendronate. That does not guarantee the combination is risk-free, so confirm with your pharmacist or doctor — especially if you take other medications or have a health condition.
Do Chitosan and Alendronate have any of the same side effects?
Yes — our sources link each of them separately to 6 of the same effects. That is not an interaction: neither changes how your body handles the other. It does mean that if one of those effects turns up, it can be harder to tell which one is behind it. They are listed on this page with the source behind each.
How far apart should I space Chitosan and Alendronate?
Chitosan can bind Alendronate in the gut and reduce how much of it you absorb, so they should not be swallowed together. The separation this page recommends is in the timing section above. Spacing them is about absorption — it is not a warning that they react with each other.
How was the Chitosan and Alendronate combination checked?
Interactions in our licensed database are recorded against drug classes. Alendronate is filed under 3 classifications, and Chitosan has documented interactions with 2 drug classes — none of Alendronate's classifications are among them. A medication can belong to classes beyond those recorded in our dataset, so this describes how the check was run rather than guaranteeing safety.
Does Chitosan interact with any other medications?
Yes. Chitosan has 3 documented drug interactions in our database — Alendronate is simply not one of them. If you take anything else, it is worth checking each one; they are all listed on this page.
Does Alendronate interact with any supplements?
Yes. Alendronate has documented interactions with 25 supplements in our database — Chitosan is not one of them. The Alendronate interaction page linked on this page lists every one, ranked by severity.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

Where next

Keep Exploring

Chitosan monograph Uses, safety profile, and every drug interaction in one place Alendronate drug information The full plain-English guide to this medication Alendronate supplement interactions Every supplement checked against Alendronate, ranked by severity Supplement interaction checker Check any supplement or product against your medications Browse medications A–Z Every drug we’ve checked against herbs & supplements References The 17 citations behind this page Ask a pharmacist Free, personal answer from our licensed team

Still Have a Question About Alendronate and Chitosan?

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This information is for education only and is not a substitute for professional medical advice. Always check with your pharmacist or doctor before starting, stopping, or combining supplements and medications.