Injections, tablets, inhalers and creams: with steroids, the form is half the story
The same steroid behaves very differently depending on how it gets into the body: an injection that lasts weeks, a daily tablet, an inhaler that reaches only the lungs, or a cream on the skin or drops in the eye. This article covers how the forms differ and how to judge which suits your cat.
- When steroids are first prescribed: what they are and why cats tolerate them
- Dosing and tapering: from tablet maths to the last dose
- Side effects: diabetes, heart and liver, and when to check what
- Injections, tablets, inhalers and creams: the form is half the story (you are here)
- When there is another disease: heart, diabetes, kidneys, infection
- A long-acting injection (methylprednisolone acetate) changes the body for weeks. Glucose and plasma volume peaked at 3-6 days and were back to baseline by 16-24 days (Ployngam 2006). Its biggest drawback is that it cannot be taken back if side effects appear.
- Tablets (prednisolone) can be adjusted daily. If side effects appear, the dose can come down the next day, which makes tablets the first choice for cats at risk of heart disease or diabetes.
- Inhaled (asthma): fluticasone 44 μg twice daily cut airway eosinophils by 74%, no different from 220 μg, with no adrenal suppression (Cohn 2010).
- Dexamethasone leans more towards diabetes than prednisolone at equal potency (Lowe 2009). For long-term use, prednisolone is better.
- Creams and eye drops are absorbed too. A kitten developed iatrogenic Cushing's from a strong human steroid lotion (clobetasol) (Chirayath 2020), and steroid eye drops raised eye pressure in 8 of 11 glaucomatous cats (Gosling 2016).
| Who | Decides |
|---|---|
| At home | Giving tablets or inhaler accurately every day, spacer training, stopping the cat licking treated skin, watching for 1-3 weeks after an injection |
| Together | Which form (whether pilling is possible, other diseases, cost), how long to overlap tablets when switching to an inhaler |
| The clinic | Giving injections, choosing doses by form, checking for corneal ulcers and herpes before eye drops |
1. The forms at a glance
| Form | Typical drugs | One dose lasts | Pros | Cons | Cat study numbers |
|---|---|---|---|---|---|
| Long-acting injection | Methylprednisolone acetate (Depo-Medrol etc.), triamcinolone | Weeks | No pilling | Cannot be withdrawn if side effects appear; no fine dose control | Plasma volume +13.4%, peak 3-6 days (Ployngam 2006). Diabetes 3.8%, heart failure 0.8% (Dutch 2023) |
| Tablets / liquid | Prednisolone | About a day (effect 12-36 h) | Adjustable daily, can be cut at once, cheap | Daily dosing, bitter taste | About 4 times the blood exposure of prednisone (Center 2013) |
| Dexamethasone | Injection, tablet | 36-54 h | Strong and long, useful in emergencies | More diabetogenic | More urine glucose at day 56 (Lowe 2009) |
| Inhaled | Fluticasone, budesonide | Twice daily | Concentrated in the lungs, few systemic effects | Cost of inhaler and spacer, 1-2 weeks to work | 44 μg cut eosinophils 74%, no adrenal suppression (Cohn 2010) |
| Creams | Hydrocortisone to clobetasol | Local | Small areas | Licked off and swallowed; absorbed if used widely or long | One case of iatrogenic Cushing's from clobetasol lotion (Chirayath 2020) |
| Eye / ear drops | Prednisolone acetate eye drops etc. | Local | Direct to the eye or ear | Worsen corneal ulcers and herpes; raise eye pressure | Eye pressure up in 8/11 glaucomatous cats (Gosling 2016) |
2. Long-acting injections: when they make sense, and when to avoid them
After one injection the drug seeps out of the muscle for 2-4 weeks. For a cat that truly cannot be pilled, that is a real solution. A 1,042-cat records study at non-immunosuppressive doses reported low risks, 3.83% diabetes and 0.82% heart failure, with no increase on repeated injections (Dutch 2023).
But one injection clearly changes the body. In 28 cats given a single 20 mg dose, glucose and insulin were up at day 15 in every group, and neither metformin nor a diabetic diet prevented it (Leal 2022). There are case reports of iatrogenic Cushing's after a short course of injections (Ferasin 2001), and of a cat whose adrenal function failed after repeated injections, with high calcium and diabetes together (Smith 2002).
- Murmur, HCM or heart medication: avoid long-acting injections and use tablets. You need to be able to cut the dose the next day.
- Obesity, previous high glucose or diabetes: avoid them. In an insulin-treated cat, one injection can unsettle glucose for weeks.
- Diseases that need a taper (IBD, pemphigus, immune-mediated anaemia): tablets, because the dose has to come down in steps.
- Pilling truly impossible, heart and glucose normal, and flare-ups only every few weeks: a long-acting injection can be a reasonable choice. Glucose and plasma volume peak at 3-6 days, so count the sleeping breathing rate daily that week.
3. Tablets: the easiest form to control
- Use prednisolone (cats absorb and convert prednisone poorly, article 1).
- Beating the bitterness: an empty gelatin capsule, a pill-pocket treat, or a flavoured compounded liquid. A bare tablet on the tongue can cause foaming and refusal next time.
- After a dry tablet, give a few ml of water or a spoonful of wet food so it does not stick in the oesophagus. Tablets often linger there in cats.
- Dose maths and tapering are in article 2.
4. Inhalers: the long-term option for asthmatic cats
Inhaled steroids reach the airways directly and spread less through the body. That matters most for asthmatic cats who also have diabetes, heart disease or kidney disease. Researchers have written that oral steroids "might be contraindicated in cats with certain infectious, endocrine, renal, or cardiac diseases" (Reinero 2006).
| Study | Subjects | Results | Notes |
|---|---|---|---|
| Cohn 2010 | Experimental asthma cats, randomised blinded crossover, fluticasone 44, 110, 220 μg twice daily | Airway eosinophils down 74%, 82%, 81% (no difference), no adrenal suppression | Evidence that the low 44 μg dose may be enough |
| Reinero 2006 | 6 healthy cats, inhaled flunisolide vs oral prednisone vs placebo, 2 weeks each | Inhaled suppressed the adrenal axis but barely affected immunity; oral reduced T and B cells | Inhaled drugs still reach the body to some degree |
| Galler 2013 | 43 real patients with asthma or bronchitis, budesonide 400 μg twice daily, 2+ months | 23 that continued improved, no side effects, adrenal suppression in 3 of 15. 20 were stopped by owners | The real-world hurdle is daily use, not efficacy |
| Verschoor-Kirss 2021 | 9 asthmatic patients randomised, inhaled fluticasone vs oral prednisolone for 8 weeks | All normalised, airway eosinophils down, fructosamine unchanged | Small pilot. Inhaled group overlapped oral for the first 7 days |
- You need a spacer chamber with a cat-sized mask. The human inhaler fits on the end.
- Shake the inhaler, puff once into the spacer, hold the mask over nose and mouth for 7-10 breaths.
- Inhaled steroids are generally thought to take 1-2 weeks to work, so tablets are often overlapped for 1-2 weeks at the start (the randomised trial above overlapped for 7 days).
- Spending the first week on mask training without the drug (with treats, 1 s, then 5 s, then 10 s) can reduce drop-outs. In the real-patient study nearly half stopped on the owner side (Galler 2013).
5. Creams, eye drops and ear drops
"It's only a cream" does not hold for cats. Cats lick off and swallow what is put on them. A Persian kitten developed iatrogenic Cushing's after prolonged use of a strong human steroid lotion (clobetasol) (Chirayath 2020).
- Do not use human creams on your own judgment. Two "steroid creams" can differ hundreds of times in strength (hydrocortisone vs clobetasol).
- Apply prescribed creams thinly and only for the set period, then prevent licking for 10-15 minutes with a cone or play.
- Eye drops: a corneal scratch or herpes keratitis can worsen with steroid drops, so the rule is to check for ulcers with fluorescein stain first. In glaucoma-prone eyes, watch eye pressure too (rise in 8/11 glaucomatous cats; minor in 2 of 5 normal cats, Gosling 2016).
- Ear drops: some ingredients must not be used with a ruptured eardrum, so the eardrum is checked first.
6. When is dexamethasone used?
Dexamethasone is about 7-8 times stronger than prednisolone and lasts longer. In emergencies (severe allergic reactions, shock, brain swelling) or for one or two injections in the clinic, that is a real advantage. As a long-term home medication it is a poorer choice. In a 14-cat study at equal potency for 56 days, dexamethasone caused more urine glucose (P=0.027) and a trend towards worse insulin response (Lowe 2009).
7. Where opinions differ
7-1. Should long-acting injections be used?
Why it divides people: a 1,042-cat practice records study says risks are low and do not rise with repeats (Dutch 2023). Physiology studies show that even one dose clearly changes glucose and plasma volume (Ployngam 2006, Leal 2022).
Our view: long-acting injections are a tool for when pilling is impossible. With heart disease, diabetes risk or a disease that needs a taper, tablets come first. The reason is not the size of the risk but whether it can be reversed.
Checking it in your cat: after an injection, log the sleeping breathing rate and water intake on days 3-6 and compare with usual.
7-2. Inhaled from the start for asthma?
Why it divides people: tablets are cheap and fast, and in a 9-cat randomised trial only oral steroids lowered airway resistance (Verschoor-Kirss 2021). Inhalers have fewer systemic effects but cost more and need training. A systematic review rated both as "good evidence" (Mueller 2021).
Our view: control a bad flare quickly with tablets, then move to an inhaler for the long term. With diabetes, heart disease or kidney disease, move to the inhaler sooner.
8. Cost: where not to save, and where you can
| Do not cut | Choose by budget | Can be skipped |
|---|---|---|
| Sleeping breathing rate log for 2 weeks after an injection or start (free); urine glucose checks on high doses | Inhaler (expensive long term) vs tablets (cheap), compounded liquids | Routine stomach protectants with steroids alone (little evidence, article 3) |
9. What to bring to the clinic
- An honest answer on pilling: how many times a day you can give a tablet is the key to choosing the form.
- Names and dates of previous injections: long-acting or not, and how many.
- Every cream, eye drop and ear drop used at home (including human products), so ingredients can be checked.
- For asthma, cough and breathing rate logs and how far inhaler training has got.
10. Read next
- Article 1 · When steroids are first prescribed
- Article 2 · Dosing and tapering
- Article 3 · Side effects
- Article 5 · When there is another disease
📌 One-line tip: when choosing a form, the question is not "how strong is it?" but "if something goes wrong, can we cut it tomorrow?"