For practitioners used to working with dermal fillers in the face, the concept is surprisingly familiar. The principle is the same. Injecting a filler product to add volume. But the anatomy, product behaviour, and patient expectations are completely different.Most practitioners in this space use either calcium hydroxylapatite (CaHA, known as Radiesse), hyaluronic acid (HA), or a combination of both.

The filler is injected into the penile shaft using a cannula technique, at varying dilutions depending on the area being treated. The goal is to increase girth, with natural-looking and natural-feeling results. So what does the latest thinking on product choice look like?

Dr. Leonardo initially worked with Radiesse alone. A 1:1 dilution for the shaft and a more dilute 2:1 ratio for the thinner-skinned distal area near the glans. That's the protocol he published in his chapter for Dr. Van Loghem's book. But since then, his approach has evolved. He now uses a hybrid formulation: CaHA blended with HA. The idea is to get the best of both products in one treatment.

"What's beautiful about it is it takes on the best characteristics of both," he explains. "You have the bio stimulation, you have the longevity. Radiesse feels like flush because it becomes you." But CaHA on its own doesn't add much bulk. And straight HA? "HA is bulky. It loves water. However, there's this very spongy quality about it." The hybrid brings longevity and natural feel from CaHA, plus the volume from HA — something neither achieves alone.

The research behind this blend traces back to Dr. Jonathan Kadouch and Nabil Fakih-Gomez's work with Belotero Volume. In the US, where Belotero Volume isn't available, practitioners are blending RHA4 with CaHA without issues. In Canada, Revanesse Contour works too.One major safety advantage: the hybrid is partially dissolvable. "If there's a little bit of contour irregularity, I can just do light dissolve with hyaluronidase and smooth that out." With pure CaHA, that option doesn't exist. Patients who switched to the hybrid from either straight Radiesse or straight HA? "They loved it. So much better." Most return every six to eight months. Not because it wore off, but because they want more.

Here's where it gets really innovative. Some men experience significant penile retraction. They're what's colloquially called "growers." This creates a problem: if you add filler to a penis that regularly shrinks back, the product can migrate and create an uneven, accordion-like effect.

Dr. Leonardo's answer?

A protocol he calls "Growtox" — injecting neurotoxin directly into the corpus cavernosum (the spongy tissue responsible for erections). He's been using this for about three years, developed together with a multidisciplinary NYC-based team of urologists, a plastic surgeon, and a dermatologist.

The mechanism: neurotoxin relaxes smooth muscle, creating a low-pressure system where blood flows in more easily and doesn't fully drain out. "You have an improvement in blood flow, and the penis doesn't empty out completely."  Three benefits in one: less shrinkage, better erectile function, and improved endurance.

Or as Dr. Leonardo puts it, "turning our growers into showers." He administers the neurotoxin two weeks before any filler treatment, which creates better conditions for even product placement during augmentation.

Standard injection risks apply: bleeding, bruising, swelling. But two complications are more specific to this procedure: vascular occlusion and priapism.For vascular safety, Dr. Leonardo uses AcuVein (a device that helps visualize veins) and 22-gauge cannulas. Most arteries in the injection plane are smaller than the cannula, which reduces the risk of accidental vascular compromise.

His philosophy on depth: "The deeper the better. If it's too superficial, you're more prone to contour irregularity." Priapism (a prolonged erection lasting more than four hours) is a known risk when using Trimix. This is an injectable blend of three medications that produces an erection without physical or emotional stimulation.

Dr. Leonardo uses Trimix during the procedure so the filler can be distributed evenly along the erect shaft. He's had a handful of priapism cases, managed stepwise: oral pseudoephedrine (a vasoconstrictor), cold application, or (in two cases) aspiration under nerve block.

His updated chapter in the forthcoming second edition of Dr. Van Loghem's book includes a refined Trimix dosing protocol after finding that standard doses were too strong for younger patients without pre-existing ED.