Contraindications — when a drug is the wrong choice

Contraindications tell you when a medicine shouldn’t be used. They’re not the same as side effects. A side effect might be annoying; a contraindication means the drug could be dangerous for you. Knowing the main types helps you avoid real risks without sounding like a pharmacist.

Common kinds of contraindications

There are two basic types: absolute and relative. Absolute means don’t use the drug at all (for example, nitrates with tadalafil or vardenafil). Relative means the drug might be okay in some situations if a doctor watches closely (like using certain blood thinners while monitoring blood tests).

Look out for these red flags: pregnancy, breastfeeding, severe liver or kidney disease, recent heart attack, history of clots, severe uncontrolled blood pressure, and known allergies to the drug class. Age matters too — older adults may need lower doses or a different drug.

Real examples you’ll recognize

- SSRIs like sertraline: avoid with MAO inhibitors; be careful if you’re on blood thinners because bleeding risk goes up.

- Benzodiazepines like lorazepam (Ativan): not a good idea for people with severe breathing problems, sleep apnea, or untreated narrow-angle glaucoma.

- Vardenafil or sildenafil (ED meds such as Zhewitra or Cialis alternatives): never combine with nitrates — that combo can cause a dangerous drop in blood pressure.

- Valsartan (Diovan): avoid during pregnancy. If you’re planning a baby or find out you’re pregnant, stop and talk to your doctor right away.

- Tranexamic acid (for heavy periods): not suitable if you have a history of blood clots or active clotting disorders.

- Steroids like deflazacort (Calcort): usually avoided if you have certain infections or recent live vaccines, and they require care in diabetes and osteoporosis.

- Antibiotics like metronidazole (Flagyl): avoid alcohol during and for 48 hours after treatment because of a disulfiram-like reaction; some alternatives exist if you can’t take it.

- Supplements and OTCs: high-dose omega-3s and some herbs can boost bleeding risk when taken with anticoagulants. Always mention supplements to your prescriber.

These examples aren’t exhaustive, but they show why reading the contraindications matters.

Quick checks before you take anything

1) Read the patient leaflet and the "Do not take" section. 2) Tell your doctor and pharmacist every prescription, OTC, and supplement you use. 3) Mention pregnancy, breastfeeding, or plans to become pregnant. 4) Ask about serious conditions like liver, kidney, heart disease, or clotting disorders. 5) Use a trusted drug interaction checker app if you want an extra layer of safety.

When in doubt, stop and ask. A quick call to your pharmacist can save a lot of trouble and keep you safer than guessing from internet posts.