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Omeprazole

Medication proton-pump inhibitor digestive
Aka: Losec, Omez, Zimor
Brands seen in Singapore: Promesec, Zenpro, Losec MUPS, Zimor, Omicap
Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.
How to use
What it’s for
Heartburn, reflux (gord) and stomach ulcers per label
When to take
Once daily per label · 30–60 min before a meal (HealthHub)
Take with
Water · capsules swallowed whole, not chewed or crushed
Pros & cons
Pros
  • NHS: once or twice a day, with or without food
  • SG: 20 mg pharmacy-only packs exist (HSA register)
  • HealthHub: relief often within days to weeks
Cons
  • Otc label: not for immediate relief — 1 to 4 days
  • NHS: may mask symptoms of serious stomach conditions
  • Long use: low magnesium, low B12, weaker bones
Sources
  1. HSA — Listing of Registered Therapeutic Products (open dataset on data.gov.sg, resource d_767279312753558cbf19d48344577084, pulled via datastore_search API; 38 omeprazole/esomeprazole rows read) · read 2026-08-27
    what it says
    “PROMESEC GASTRO-RESISTANT CAPSULES 20 MG (PHARMACY ONLY) · Pharmacy Only — ZENPRO CAPSULE 20MG (PHARMACY ONLY) · Pharmacy Only — LOSEC MUPS TABLET 20 mg · Prescription Only — ZIMOR 20 CAPSULE 20 mg · Prescription Only”
  2. HSA — List of reclassified medicines (forensic classification definitions: POM / P / GSL) · read 2026-08-27
    what it says
    “Pharmacy-Only Medicine (P): A therapeutic product that can be obtained from a pharmacist at a retail pharmacy without a prescription … Prescription-Only Medicine (POM): … can only be obtained from a doctor or from a pharmacist with a valid prescription”
  3. HealthHub (MOH Singapore) — Omeprazole medication information leaflet (article last reviewed 12 June 2026) · read 2026-08-27
    what it says
    “Omeprazole is used to treat various conditions of the gastrointestinal … tract including: Gastro-oesophageal reflux disease … Ulcers of the gastrointestinal tract … Take this medication 30 to 60 minutes before a meal. Capsules should be swallowed whole with water”
  4. HealthHub (MOH Singapore) — Omeprazole leaflet, precautions and side-effects sections (same page) · read 2026-08-27
    what it says
    “Inform your healthcare professional if: … You are pregnant, planning to become pregnant, or breastfeeding … may cause the level of magnesium in your body to decrease if you use it for long duration”
  5. HealthHub (MOH Singapore) — Omeprazole leaflet, length-of-treatment section (same page) · read 2026-08-27
    what it says
    “The length of treatment with omeprazole depends on your condition and how well you respond to the medication … Most people experience relief within the first few days to weeks of starting omeprazole”
  6. HealthHub (MOH Singapore) — Omeprazole leaflet, food and medication interactions section (same page) · read 2026-08-27
    what it says
    “Certain blood thinners (e.g. warfarin, clopidogrel) … Certain anti-fungal medicines (e.g. ketoconazole) … Certain drugs to treat seizures (e.g. phenytoin) … Other medicines such as digoxin, cyclosporin, methotrexate and iron salts”
  7. NHS — Omeprazole: a medicine to treat heartburn and indigestion (page last reviewed 17 September 2025) · read 2026-08-27
    what it says
    “Omeprazole is a medicine called a proton pump inhibitor (PPI). It reduces the amount of acid in your stomach … It's usually taken once or twice a day … you can take it with or without food”
  8. NHS — Omeprazole, 'How to take omeprazole' important box (same page) · read 2026-08-27
    what it says
    “Do not take omeprazole for longer than 2 weeks if you bought it without a prescription … Taking omeprazole can make it harder to notice symptoms of some serious conditions”
  9. NHS — Omeprazole, 'Who can and cannot take omeprazole' and 'Serious side effects' (same page) · read 2026-08-27
    what it says
    “it may not be suitable if … you have a kidney or liver condition … you have osteoporosis (weakened bones) … having a very low level of vitamin B12 … weakened bones, which can break more easily”
  10. NHS — Omeprazole, 'Taking omeprazole with other medicines, food and drink' (same page) · read 2026-08-27
    what it says
    “some medicines to prevent blood clots, such as warfarin and clopidogrel … the sedative diazepam … the anti-seizure medicine phenytoin … the herbal remedy for low mood, St John's Wort … HIV medicines called nelfinavir and atazanavir”
  11. DailyMed / FDA — PRILOSEC OTC (omeprazole magnesium 20 mg) delayed-release tablet, OTC Drug Facts 'Uses' (label updated 29 July 2026) · read 2026-08-27
    what it says
    “treats frequent heartburn (occurs 2 or more days a week) … not intended for immediate relief of heartburn; this drug may take 1 to 4 days for full effect”
  12. DailyMed / FDA — PRILOSEC OTC, OTC Drug Facts 'Directions' (same label) · read 2026-08-27
    what it says
    “swallow 1 tablet with a glass of water before eating in the morning … do not take more than 1 tablet a day … do not use for more than 14 days unless directed by your doctor”
  13. DailyMed / FDA — PRILOSEC OTC, OTC Drug Facts 'Warnings' (same label) · read 2026-08-27
    what it says
    “Do not use if you have: trouble or pain swallowing food, vomiting with blood, or bloody or black stools … Ask a doctor before use if you have: had heartburn over 3 months … unexplained weight loss”
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Updated 2026-08-29. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.