Active Ingredients A to Z

Every branded generic we stock, organised by active ingredient, so you can find the affordable alternative to any big-name original. The brand changes; the active ingredient does not.

Ofloxacin Ofloxacin is a fluoroquinolone antibiotic available as tablets and as eye or ear drops. Oral and injectable forms carry boxed warnings for tendon rupture, aortic aneurysm or dissection, and nerve damage. 2 medicines View Ofloxacin Olanzapine Olanzapine is an atypical antipsychotic used for schizophrenia and bipolar disorder. It causes more weight gain than most other antipsychotics, along with raised blood sugar and cholesterol, so regular metabolic monitoring is essential. 1 medicine View Olanzapine Olmesartan Olmesartan is an angiotensin receptor blocker (ARB) used for high blood pressure. It is contraindicated in pregnancy and can rarely cause severe, sprue-like bowel disease with chronic diarrhoea and weight loss. 4 medicines View Olmesartan Ondansetron Ondansetron is a serotonin 5-HT3 receptor blocker used to prevent nausea and vomiting from chemotherapy, radiotherapy and surgery. It can prolong the heart's QT interval, so it needs caution in people with heart rhythm problems or low potassium or magnesium. 1 medicine View Ondansetron Orlistat Orlistat is a weight-loss medicine that blocks fat absorption in the gut, causing oily stools and urgent bowel movements after fatty meals, and reducing absorption of fat-soluble vitamins. 1 medicine View Orlistat Ornidazole Ornidazole is a nitroimidazole antimicrobial used to treat bacterial vaginosis, trichomoniasis, amoebiasis and giardiasis. Alcohol should be avoided during treatment, and prolonged or high-dose use has been linked to nerve damage and seizures. 1 medicine View Ornidazole Oseltamivir Oseltamivir is an antiviral used to treat and prevent influenza. It works best when started within 48 hours of symptoms starting, and has been linked to confusion or unusual behaviour, reported more often in children. 1 medicine View Oseltamivir Oxcarbazepine Oxcarbazepine is an anticonvulsant used to control focal seizures. It can cause low blood sodium and, in people of certain Asian ancestries carrying the HLA-B*1502 gene, a serious risk of severe skin reactions. 1 medicine View Oxcarbazepine Oxybutynin Oxybutynin is an anticholinergic that relaxes the bladder muscle to treat overactive bladder and urge incontinence. It must be avoided in narrow-angle glaucoma and urinary retention, since it can worsen both. 2 medicines View Oxybutynin Oxytetracycline Oxytetracycline is a tetracycline antibiotic used for infections such as acne, chest infections and chlamydia. It must be avoided during pregnancy and in children under 8, since it can permanently discolour developing teeth and affect bone growth. 1 medicine View Oxytetracycline