# Enlarged Prostate in Dogs: Medicines That Help Benign prostatic hyperplasia (BPH) is the most common prostate problem in intact male dogs, and it is not cancer. A dog medicine for enlarged prostate can shrink the gland or ease symptoms, and the two drugs most often used in the United States are finasteride and osaterone acetate. Castration remains the treatment of choice for dogs not used for breeding [1]. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## Quick Answer - BPH affects more than 95% of intact male dogs, and most stay symptom-free until the prostate grows large enough to cause signs [2]. - Castration is the treatment of choice for dogs not intended for breeding or showing, and it resolves the problem at its source [1]. - For breeding dogs, medical therapy works well, but it only controls BPH while treatment continues [1]. - Finasteride and osaterone acetate are the two drugs with the strongest evidence for shrinking the prostate while preserving fertility [3]. - Any prostate medicine for a dog requires a veterinary diagnosis first, because prostate cancer, infection, and cysts can look similar [4]. ## What Dog Medicine for Enlarged Prostate Is and What It Treats The prostate sits behind the bladder and wraps around the urethra. In an intact male dog, testosterone and other hormones drive the gland to grow as the dog ages. That growth is BPH, a spontaneous, age-related, noncancerous enlargement of the prostate [1]. It has never been reported in cats [1]. BPH itself is rarely life-threatening, but a big prostate presses on nearby structures. Owners often notice blood in the urine, blood in the semen, or a bloody discharge from the sheath [1]. Some dogs strain to defecate, have ribbon-like stools, or seem uncomfortable when they sit. Others show no signs at all, and the problem turns up during a routine exam [1]. Veterinarians use prostate medication to shrink the gland, ease those signs, and avoid surgery, especially in dogs still used for breeding [5]. Drug therapy does not cure BPH. It manages it. If you stop the medicine, the prostate grows back, because the hormones that caused the problem are still there [1]. Several conditions can mimic BPH, including bacterial prostatitis, prostatic cysts, abscesses, and prostate cancer [4]. Your veterinarian will likely use transabdominal ultrasound, which is the best way to judge prostate size and texture, plus urine or prostatic fluid testing to sort out the diagnosis [1][4]. ## How Prostate Medication for Dogs Works ### Finasteride Finasteride blocks an enzyme that converts testosterone into a more potent form called dihydrotestosterone. Less dihydrotestosterone means less stimulation for the prostate cells, so the gland gradually shrinks. In a study of dogs with BPH, two months of finasteride treatment changed prostate blood flow and volume as measured by Doppler ultrasound [6]. Finasteride is widely used in the United States for BPH in breeding dogs. A systematic review of 35 studies found that finasteride and osaterone acetate are acceptable treatments for BPH in breeding dogs, though the exact size of the benefit is still debated [3]. ### Osaterone acetate Osaterone acetate works differently. It blocks androgen receptors and also has progestin-like effects, so the prostate loses hormonal stimulation. The same review supports it as a reasonable option when you want to keep a dog fertile [3]. ### Other drugs and supplements Tamoxifen and a few other drugs have been studied for canine BPH, but the evidence is thinner than for finasteride and osaterone [3]. An extract of Epilobium parviflorum, a plant sometimes called willowherb, reduced prostate volume by about 40% in two dogs treated for 60 days, with no side effects reported during that period [7]. That is a very small case report, so it is not well established as a standard treatment. Ask your veterinarian before giving any supplement, because products sold online are not held to drug standards. ## Dosing Basics for Dog Medicine for Enlarged Prostate Your veterinarian decides the dose. It is calculated from your dog's weight, overall health, and how severe the prostate enlargement is. Do not borrow a dose from another dog or from a human prescription. Finasteride is given by mouth, usually once daily. Osaterone acetate is also given by mouth, often once daily for a set number of days, then tapered. Your veterinarian will tell you the exact schedule. Give the medicine with or without food as directed. If your dog spits it out or vomits right after, call your vet before repeating the dose. If you miss a dose, give it when you remember, unless it is almost time for the next one. Then skip the missed dose and go back to your normal schedule. Never double up to catch up. Expect weeks, not days. In the finasteride study, dogs were treated for two months before researchers measured the effects [6]. The Epilobium case report also ran for 60 days [7]. Plan on a recheck with ultrasound to see whether the prostate is actually shrinking. ## Side Effects: Common and Serious | Side effect | How common or serious | What to do | |---|---|---| | Reduced fertility or semen quality | Expected with hormone-blocking drugs, reversible in many dogs after stopping | Discuss breeding plans with your vet before starting | | Vomiting or poor appetite | Uncommon, usually mild | Offer small meals, call your vet if it lasts more than a day | | Lethargy or behavior change | Uncommon | Note the timing and call your vet | | Prostate shrinking too slowly or signs returning | Possible, since drugs control but do not cure BPH | Schedule the recheck ultrasound your vet recommends | | Blood in urine that gets worse | Serious, could mean infection, cyst, or cancer | Call your vet the same day | | Straining to urinate with little or no urine | Emergency, suggests urinary blockage | Go to an emergency clinic now | The two-drug comparison review notes that side effects and safety need careful analysis to keep owners and dogs sticking with treatment [5]. In the Epilobium report, no side effects appeared over 60 days, but that involved only two dogs [7]. One practical point about finasteride: it lowers dihydrotestosterone, so it can affect prostate size readings and semen quality. Your vet may want to check hormone levels or sperm quality if you plan to breed. ## Who Should Not Take These Drugs and What Interacts With Them Dogs with liver disease need extra caution, because these drugs are processed by the liver. Your veterinarian may run blood work first. Do not give finasteride or osaterone to a dog that has already been neutered for a prostate problem without a clear diagnosis. BPH does not occur in castrated dogs, so prostate disease in a neutered male points to something else, such as infection or cancer [4]. Pregnant women should not handle finasteride tablets, especially crushed ones. The drug can affect a developing male fetus. Wash your hands after giving any dose, and keep tablets away from children. Tell your veterinarian about every other drug, supplement, or topical product your dog takes. Hormone-based medicines can interact with other hormone treatments, and steroids or progestins may change how well they work. Your vet can check for interactions before prescribing. If your dog has a swollen paw or joint problem at the same time, do not reach for human pain relievers. Some, like ibuprofen, are toxic to dogs. For safe options, see [Dog Arthritis Medication](/knowledge/veterinary-medicine/clinical-methods/dog-arthritis-medication). If the swelling is in a paw, [Swollen Dog Paw: Comprehensive Veterinary Reference Guide](/knowledge/veterinary-medicine/preventive-care/swollen-dog-paw) explains what to look for. ## Overdose: When to Call for Help If your dog eats several tablets at once, call your veterinarian or a pet poison hotline right away. Signs of overdose are not well documented for these drugs in dogs, so treat any extra dose as an emergency and get professional guidance. Have the bottle ready so you can tell the veterinarian the drug name, the strength of each tablet, and how many your dog may have swallowed. Do not make your dog vomit unless a veterinarian tells you to. ## Limitations and When to Contact a Veterinarian Medical therapy for BPH has real limits. It controls the problem only while you keep giving the drug, and it does not remove the hormonal drive behind the enlargement [1]. Castration does, which is why it remains the treatment of choice for dogs not used for breeding [1]. Call your veterinarian the same day if you see blood in the urine that is new or worsening, straining to defecate that seems painful, a swollen or tense belly, or a discharge from the sheath that smells bad. These can point to prostatitis, a cyst, or an abscess instead of simple BPH [4]. Go to an emergency clinic now if your dog strains to urinate and produces little or no urine, cries out when urinating, or seems to be in severe pain. A prostate that blocks the urethra is a true emergency. Schedule a routine visit if your dog has been on medication for a few weeks and you have not seen improvement, or if you notice new signs like weight loss or trouble walking. Your veterinarian will recheck the prostate with ultrasound and decide whether to adjust the plan [1]. Every dog is different, and only your veterinarian can examine your dog, review the test results, and set the right treatment. ## Frequently Asked Questions ### Can an enlarged prostate in a dog be cured with medicine? No, medicine controls BPH but does not cure it. The prostate shrinks while your dog takes the drug and grows again if you stop, because the hormones driving the enlargement are still present [1]. Castration removes that drive and is the treatment of choice for dogs not used for breeding [1]. ### Is finasteride safe for a breeding dog? Finasteride is considered an acceptable treatment for BPH in breeding dogs, based on a review of 35 studies [3]. It can affect semen quality and hormone levels, so work with a veterinarian who can monitor your dog's fertility during treatment. ### How long does it take for prostate medicine to work? Expect a matter of months, not days. In one study, dogs received finasteride for two months before prostate changes were measured [6]. A separate case report saw prostate volume drop by about 40% after 60 days of treatment [7]. Your veterinarian will schedule rechecks to track progress. ### Does my dog need to be neutered if he takes prostate medicine? Not always. Castration is the treatment of choice for dogs not intended for breeding or showing, and it is the most reliable fix [1]. If your dog is a breeding prospect, medical therapy can manage BPH while preserving fertility, as long as you continue treatment [1][3]. ### What if my dog still has blood in his urine after treatment starts? Blood in the urine is one of the most common signs of BPH, so some improvement is expected over time [1]. If it persists or gets worse, call your veterinarian. It can signal a urinary infection, a prostatic cyst, or another condition that needs a different treatment [4]. ## Related Articles - [Dog Swollen Paw Home Remedy](/knowledge/veterinary-medicine/clinical-methods/dog-swollen-paw-home-remedy) - [Dog Arthritis Medication](/knowledge/veterinary-medicine/clinical-methods/dog-arthritis-medication) - [Swollen Dog Paw: Comprehensive Veterinary Reference Guide](/knowledge/veterinary-medicine/preventive-care/swollen-dog-paw) - [One Swollen Dog Paws Home Remedy](/knowledge/veterinary-medicine/clinical-methods/one-swollen-dog-paws-home-remedy) - [Dog Swollen Lymph Nodes Treatment Home Remedies](/knowledge/veterinary-medicine/clinical-methods/dog-swollen-lymph-nodes-treatment-home-remedies) - [Dog Licking Paws Medicine](/knowledge/veterinary-medicine/clinical-methods/dog-licking-paws-medicine) - [Prostate Cysts in Dogs: Symptoms and Treatment](/knowledge/veterinary-medicine/senior-and-chronic-care/prostate-cysts-dogs) - [Dog Leaky Bladder Medicine: Drugs for Urinary Control](/knowledge/veterinary-medicine/digestive-and-urinary-care/dog-leaky-bladder-medicine) - [What Can I Give My Dog for a UTI? Antibiotics and Safe Care](/knowledge/veterinary-medicine/digestive-and-urinary-care/dog-uti-medicine-antibiotics) ## References 1. [Benign Prostatic Hyperplasia in Dogs - Reproductive System](https://www.merckvetmanual.com/reproductive-system/prostatic-diseases-in-small-animals/benign-prostatic-hyperplasia-in-dogs). Merck Veterinary Manual. 2. [Grading Canine Benign Prostatic Hyperplasia: A Survey of Veterinary Practice and the Development of a Web-Based Symptom Index](https://pubmed.ncbi.nlm.nih.gov/42791690/). Animals : an open access journal from MDPI, 2026. 3. [A Systematic Review of Medical Treatments for Benign Prostatic Hyperplasia in Dogs: Evaluating Strategies for Reproductive Function Preservation](https://pubmed.ncbi.nlm.nih.gov/39852945/). Veterinary sciences, 2025. 4. [Prostatic Diseases in Small Animals - Reproductive System](https://www.merckvetmanual.com/reproductive-system/prostatic-diseases-in-small-animals/prostatic-diseases-in-small-animals). Merck Veterinary Manual. 5. [Diagnosis and Treatment of Benign Prostatic Hyperplasia in Dogs: New Approaches](https://pubmed.ncbi.nlm.nih.gov/40687184/). Veterinary medicine international, 2025. 6. [Doppler Ultrasonography in the Diagnosis of Dogs With Benign Prostatic Hyperplasia and Investigation of the Efficacy of Finasteride in Treatment](https://pubmed.ncbi.nlm.nih.gov/40260998/). Veterinary medicine and science, 2025. 7. [Use of Epilobium parviflorum in the Treatment of Benign Prostatic Hyperplasia in Canines](https://pubmed.ncbi.nlm.nih.gov/40033986/). Veterinary medicine and science, 2025. ## Further Reading - [American Veterinary Medical Association: First Aid Tips for Pet Owners](https://www.avma.org/resources-tools/pet-owners/emergencycare/first-aid-tips-pet-owners) - [Merck Veterinary Manual: Dog Owners](https://www.merckvetmanual.com/dog-owners) - [Cornell Richard P. Riney Canine Health Center: Canine Health Information](https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information)