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Pioglitazone is a glitazone that lowers blood sugar in type 2 diabetes by making the body's cells more sensitive to insulin. On its own it hardly ever causes hypoglycaemia, but it makes the body retain water: oedema and weight gain are common, and it must not be used in people with current or previous heart failure. In Germany, it has for years been prescribable on statutory health insurance only in restricted cases.
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Besides the heart, there are four areas that should be kept in view during long-term treatment with pioglitazone. None of these risks is common, but all of them can be detected early with simple attentiveness.
In studies, more bone fractures occurred on pioglitazone, mainly in women and typically in the forearm, hand, lower leg and foot.¹ For women after the menopause and for people with known osteoporosis, the fracture risk therefore belongs in the weighing-up. Background in the guide medications and osteoporosis risk.
A review by the European Medicines Agency concluded in 2011 that pioglitazone is associated with a slightly increased risk of bladder cancer. According to this assessment, the benefit continues to outweigh the risk in suitable patients, but additional contraindications were introduced.⁴ Pioglitazone must not be used with current or previous bladder cancer or with visible blood in the urine that has not been investigated. What matters for you: blood in the urine, pain when passing urine or a sudden urge to urinate while on pioglitazone should be checked by a doctor promptly.
Rarely, macular oedema can develop or get worse — fluid retention at the point of sharpest vision. Many of those affected also have oedema in their legs. If you newly notice blurred vision or see straight lines as distorted, have an eye specialist check whether the retina is involved — in diabetes this is part of the regular check-ups anyway.¹
Liver values are measured before treatment begins; according to the SmPC, treatment should not be started if the baseline values are markedly raised, and pioglitazone is contraindicated with impaired liver function. During treatment, checks are made as the doctor sees fit. Persistent nausea, vomiting, upper abdominal pain, unusual tiredness, loss of appetite or dark urine are reasons for a prompt check.¹ The flip side is interesting: in studies, pioglitazone improved inflammatory fatty liver disease; however, it is not licensed for this in Germany.
Pioglitazone is broken down mainly via the liver enzyme CYP2C8. In everyday life, however, combinations that also cause fluid retention or affect blood sugar are more relevant than classic enzyme interactions.¹
| Combination | Consequence | What to do |
|---|---|---|
| Insulin | More oedema, higher heart failure risk; hypoglycaemia | Only with close monitoring; the insulin dose often needs adjusting |
| Sulfonylureas such as glimepiride | Hypoglycaemia | Measure blood sugar more often, reduce the dose if needed |
| Anti-inflammatory painkillers such as ibuprofen, diclofenac, naproxen | Additional salt and water retention, strain on the kidneys and heart | Only briefly if possible; discuss alternatives, see painkillers compared |
| Calcium channel blockers such as amlodipine | Also cause ankle oedema — the cause is then hard to pin down | Do not be too quick to blame one medicine for the oedema; record your weight as well |
| Gemfibrozil (a lipid-lowering agent) | Inhibits CYP2C8, pioglitazone levels rise markedly | According to the SmPC, reduce the dose if needed and monitor closely |
| Rifampicin | Speeds up breakdown, weaker effect | Check blood sugar, adjust the dose if needed |
| Cortisone such as prednisolone | Blood sugar rises, additional fluid retention possible | Measure blood sugar closely |
| Alcohol | Strains the liver; with insulin or sulfonylureas, risk of hypoglycaemia | Restraint |
Particularly in type 2 diabetes with high blood pressure, joint pain and heart problems, medicines that each cause a little fluid retention quickly accumulate. An up-to-date medication plan and an interaction check before every new prescription — including over-the-counter painkillers — make such cumulative effects visible.
In recent years, diabetes medicines have arrived that not only lower blood sugar but, in studies, also protect the heart and kidneys. For people with heart failure or a high risk of it, this — the opposite of what pioglitazone brings with it — is particularly valuable.²
| Drug group | Example | Heart failure | Weight |
|---|---|---|---|
| Glitazone | Pioglitazone | Increased risk, contraindicated in heart failure | Gain |
| SGLT2 inhibitors | Empagliflozin, dapagliflozin | Fewer hospital admissions for heart failure; also licensed for treating heart failure | Slight loss |
| GLP-1 receptor agonists | Semaglutide, liraglutide | Not increased; benefit in vascular disease demonstrated | Loss |
| DPP-4 inhibitors | Sitagliptin, linagliptin | Neutral for these two | Neutral |
| Sulfonylureas | Glimepiride | No particular effect | Gain, hypoglycaemia |
To be fair, pioglitazone still has properties that can play a role in individual cases: on its own it hardly ever causes hypoglycaemia, it acts specifically on insulin resistance and it has been tried and tested for a long time. In a study of insulin-resistant people without diabetes after a stroke (IRIS), there were fewer repeat strokes and heart attacks on pioglitazone — but at the price of more weight gain, oedema and bone fractures, and it is not licensed for this use.
Since the early 2010s, the Federal Joint Committee (G-BA, the body that decides what statutory health insurance covers) has excluded glitazones from prescription at the expense of statutory health insurance in its Pharmaceuticals Directive (Annex III), because it did not consider their benefit over other treatments to be adequately demonstrated.⁵ For you, this means:
Pioglitazone is not used during pregnancy or breastfeeding; for diabetes in pregnancy, insulin is usually the treatment of choice.¹,⁶ One special point concerns women with PCOS (polycystic ovary syndrome): because pioglitazone improves the effect of insulin, ovulation that had previously stopped can resume — pregnancy becomes possible, even if it has not happened before. According to the SmPC, the women concerned should be informed about this; if a pregnancy is planned or has occurred, pioglitazone is stopped. General information is in the guide medications during pregnancy.
With age, the risks that weigh most heavily with pioglitazone increase: heart failure, bone fractures and — through oedema and dizziness — falls. The SmPC recommends starting with the lowest dose and increasing cautiously, especially in combination with insulin. In older people, the treatment is reviewed particularly regularly to see whether the benefit still outweighs the risks.¹
With impaired kidney function, no dose adjustment is usually needed; according to the SmPC there are insufficient data for patients on dialysis, so pioglitazone is not used in that setting. Impaired kidney function does, however, favour fluid retention. With impaired liver function, pioglitazone is contraindicated.¹
Usually not, but it is a signal you should take seriously. Mild swelling in the evening that goes down overnight is common on pioglitazone. What matters is how it develops: if the swelling is still there in the morning, rises higher up the leg, or your weight increases markedly within a few days, more water is being retained than your body can balance out. If shortness of breath, breathlessness when lying down or a cough at night are added, the heart may be affected — then have it checked by a doctor the same day. Weighing yourself every day and taking a quick look at your ankles is the simplest early warning.
That is typical of pioglitazone and has two reasons: the medicine promotes the storage of fat in the tissue under the skin, and it causes water retention. The first part is not necessarily unfavourable for metabolism, because at the same time less fat ends up in the liver and abdomen. The second part is the critical one. You can roughly tell them apart by the pace: water comes quickly, over days; fat slowly, over weeks and months. Discuss the gain with your practice — it is a legitimate reason to reconsider the treatment, especially if you should be losing weight anyway.
That is not down to your particular insurer but to a nationwide rule: glitazones can only be prescribed on statutory health insurance in justified exceptional cases. You have two options. Either your practice sees a medically justified individual case in your situation and prescribes it on a statutory insurance prescription with a written justification, or you switch together to an alternative that is reimbursed. Several drug groups are available for this today, some of which also protect the heart and kidneys. The only important thing is not to simply stop, but to plan the switch and monitor your blood sugar more closely during the changeover.
The interaction check shows which of your medicines add up when it comes to oedema and blood sugar.
