Short answer: It can. Orlistat (Xenical) blocks some fat absorption, and its label says it lowers absorption of some fat-soluble vitamins and beta-carotene. In trials without supplements, low vitamin D on two or more visits was seen in 12.0% on Xenical versus 6.6% on placebo. The label advises a daily multivitamin with vitamins A, D, E and K, taken at least 2 hours apart from Xenical, such as at bedtime.
| Vitamin | Placebo | Xenical |
|---|---|---|
| Vitamin A | 1.0% | 2.2% |
| Vitamin D | 6.6% | 12.0% |
| Vitamin E | 1.0% | 5.8% |
| Beta-carotene | 1.7% | 6.1% |
In the 1-year adolescent study, where everyone took vitamin supplements, low vitamin D was seen in 1.4% on Xenical versus 0.7% on placebo. The label also says Xenical reduced absorption of a beta-carotene supplement and blocked absorption of a vitamin E acetate supplement, and that its effect on supplemental vitamin D, vitamin A and vitamin K from food is not known. It notes that vitamin D and beta-carotene levels may already be low in people with obesity.
The label says patients should be strongly encouraged to take a multivitamin that contains fat-soluble vitamins (A, D, E, K and beta-carotene), once a day, at least 2 hours before or after Xenical, such as at bedtime. Xenical itself is one 120 mg capsule three times a day with each main meal that contains fat, during or up to 1 hour after the meal, so a bedtime vitamin keeps the two apart.
| Medicine | What the label says |
|---|---|
| Levothyroxine | Underactive thyroid reported after approval; take at least 4 hours apart and monitor thyroid function |
| Warfarin and other anticoagulants | Vitamin K absorption may fall; changes in INR reported; monitor clotting tests closely |
| Cyclosporine | Levels fell; take at least 3 hours before or after Xenical |
| Amiodarone | Lower exposure seen; reduced effect possible |
| Seizure medicines | Convulsions reported; watch for changes in seizure frequency |
| HIV medicines | Loss of viral control reported with several antiretrovirals |
For diabetes, the label says weight loss may change blood sugar control and that some people may need a lower dose of sulfonylureas or insulin.
Your prescriber or pharmacist can say how Xenical fits with your other medicines and whether vitamin levels should be checked. Useful notes: the time of each Xenical dose, the multivitamin time, any levothyroxine or warfarin doses, and recent vitamin D or INR results. Dose Track can set a reminder for each meal dose and a separate bedtime reminder for the multivitamin. For the thyroid side of the timing, see calcium and iron with levothyroxine.
Read more on Dose Track: Xenical side effects · Multivitamins · Vitamin D3 · Vitamin E · Weight loss