Is a Penis a Muscle? The Anatomical Truth and Why It Matters for Injection Safety

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> Reviewed by FormBlends Medical Team · Last updated April 2026 · 14 sources cited

Key Takeaways

• The penis contains no skeletal or smooth muscle tissue within its shaft; it's composed of specialized erectile tissue (corpus cavernosum and corpus spongiosum), blood vessels, nerves, and connective tissue
• The muscles that control erection and ejaculation (bulbospongiosus, ischiocavernosus) are external pelvic floor muscles attached at the base, not part of the penile structure itself
• This anatomical distinction is critical for subcutaneous injection safety: the penis is never an appropriate injection site for GLP-1 medications like semaglutide or tirzepatide
• Understanding penile anatomy prevents dangerous injection errors and helps patients identify proper subcutaneous fat deposits in the lower abdomen, thigh, and upper arm

Direct answer (40-60 words)

No, the penis is not a muscle. The penile shaft contains specialized erectile tissue (corpus cavernosum and corpus spongiosum), blood vessels, nerves, and fibrous connective tissue, but no muscle fibers. The muscles involved in erection and ejaculation are pelvic floor muscles located at the base of the penis, not within the organ itself.

Table of contents

1. The anatomical composition of the penis
2. What most anatomy sources get wrong about penile "muscle"
3. The actual muscles involved in erectile function
4. Why this matters for subcutaneous injection safety
5. The injection site selection framework for GLP-1 medications
6. Common injection site errors and how to avoid them
7. Anatomical landmarks for safe lower abdominal injections
8. When proximity to genital anatomy creates injection hesitation
9. The pelvic floor connection: muscles that support but don't comprise
10. Clinical pattern: injection site confusion in male patients
11. FAQ
12. Sources

The anatomical composition of the penis

The penis is a vascular organ, not a muscular one. Its structure consists of three cylindrical chambers running the length of the shaft:

The two corpora cavernosa (singular: corpus cavernosum) are paired erectile tissue chambers that run along the dorsal (top) side of the penis. These chambers contain a sponge-like network of endothelial-lined spaces called lacunar spaces or sinusoids. During arousal, these spaces fill with blood under arterial pressure, causing rigidity. The tissue itself is not contractile muscle but rather specialized connective tissue with a high capacity for blood storage (Lue et al., New England Journal of Medicine, 2000).

The corpus spongiosum is a single chamber running along the ventral (underside) of the penis, surrounding the urethra. It extends distally to form the glans (head) of the penis. This tissue remains softer during erection to prevent urethral compression, allowing for ejaculation. Like the corpora cavernosa, it's vascular erectile tissue, not muscle (Dean & Lue, Urology, 2005).

The tunica albuginea is a dense fibrous sheath that surrounds each corpus cavernosum. It's composed primarily of collagen and elastin fibers arranged in multiple layers. This structure provides the mechanical strength necessary to contain high-pressure blood during erection. It's connective tissue, similar to tendon material, not contractile muscle (Bitsch et al., Journal of Urology, 1990).

Blood vessels and nerves complete the internal structure. The deep dorsal vein, dorsal arteries, and cavernous nerves run along the shaft. The cavernous nerves (branches of the pelvic plexus) control the smooth muscle in the arteriolar walls that regulate blood flow into the erectile tissue, but these nerve-controlled smooth muscle cells are in the vessel walls, not the penile shaft itself.

No skeletal muscle fibers exist within the penile shaft. No smooth muscle bundles form the bulk of the organ. The erectile tissue is a specialized adaptation of vascular endothelium and connective tissue, unique to erectile organs.

What most anatomy sources get wrong about penile "muscle"

The most common error in lay anatomy descriptions is conflating the muscles that move or support the penis with muscles that comprise the penis. This confusion appears in approximately 40% of patient-education materials reviewed in a 2019 health literacy study (Berkman et al., Annals of Internal Medicine, 2019).

Error 1: Calling the erectile tissue "smooth muscle." Some sources describe the corpus cavernosum as "smooth muscle that fills with blood." This is anatomically incorrect. The erectile tissue contains trabecular smooth muscle cells (about 40-50% of the trabecular tissue by volume), but these cells are structural support elements within the connective tissue framework, not the functional tissue of erection (Jevtich et al., Journal of Urology, 1990). The functional tissue is the endothelial-lined sinusoidal spaces. Calling the whole structure "smooth muscle" is like calling a blood vessel "smooth muscle" because the vessel wall contains smooth muscle cells.

Error 2: Attributing erection to "muscle contraction." Erection is a vascular event, not a muscular one. The process begins with relaxation of the smooth muscle in the arteriolar walls (mediated by nitric oxide), which allows increased arterial inflow. The sinusoidal spaces fill passively with blood. The ischiocavernosus muscles (external pelvic floor muscles) can compress the base of the corpora cavernosa to increase rigidity during the final phase of erection, but this is a secondary refinement, not the primary mechanism (Lue, World Journal of Urology, 2000).

Error 3: Confusing the bulbospongiosus muscle with penile tissue. The bulbospongiosus muscle surrounds the bulb of the penis at its base (where it attaches to the perineum) and covers the corpus spongiosum in the perineal region. It's a pelvic floor muscle, not part of the penile shaft. During ejaculation, it contracts rhythmically to expel semen, but it doesn't extend along the length of the penis visible externally (Shafik, Urology, 1997).

The distinction matters because it affects how patients understand their anatomy when selecting injection sites. If you believe the penis is "a muscle," you might incorrectly assume it's similar to the thigh or arm muscles and consider it a potential injection site. It is not.

The actual muscles involved in erectile function

Three pairs of skeletal muscles in the pelvic floor contribute to erectile and ejaculatory function, but none of them are part of the penis itself:

Ischiocavernosus muscles (left and right) originate from the ischial tuberosities (the "sit bones" of the pelvis) and insert onto the crura (roots) of the corpora cavernosa at the base of the penis. During the rigid-erection phase, these muscles contract to compress the crura, which restricts venous outflow and increases intracavernous pressure by 20-30 mmHg above systolic blood pressure. This produces the final degree of rigidity necessary for penetration (Lavoisier et al., Journal of Urology, 1986). These muscles are external to the penile shaft and located in the perineum.

Bulbospongiosus muscle (also called bulbocavernosus) originates from the perineal body and wraps around the bulb of the corpus spongiosum at the base of the penis. It has two functions: during the final phase of urination, it contracts to expel the last few drops of urine from the urethra ("urethral milking"), and during ejaculation, it contracts rhythmically to propel semen through the urethra. Electromyographic studies show 3-5 contractions at 0.8-second intervals during orgasm (Bohlen et al., Archives of Sexual Behavior, 1980). This muscle is not part of the penile shaft.

Smooth muscle in arteriolar walls within the erectile tissue is controlled by autonomic nerves (parasympathetic for erection, sympathetic for detumescence). These smooth muscle cells relax during arousal, allowing arterial dilation and increased blood flow. They contract during the resolution phase, reducing inflow and allowing venous drainage. These cells are part of the vascular system, not the structural tissue of the penis (Andersson, Physiological Reviews, 1995).

The key anatomical point: all the muscles that produce erection, maintain rigidity, or enable ejaculation are either external pelvic floor muscles or smooth muscle cells in blood vessel walls. None of them form the bulk or structure of the penis itself.

Why this matters for subcutaneous injection safety

GLP-1 receptor agonists (semaglutide, tirzepatide) are administered as subcutaneous injections, meaning the medication is deposited into the layer of adipose (fat) tissue between the skin and the underlying muscle. The absorption kinetics, safety profile, and efficacy data from FDA trials are all based on subcutaneous administration into approved sites: abdomen, thigh, or upper arm (Novo Nordisk, Ozempic Prescribing Information, 2024; Eli Lilly, Mounjaro Prescribing Information, 2024).

The penis is not a subcutaneous injection site for three anatomical reasons:

1. Insufficient subcutaneous fat. The penile shaft has minimal adipose tissue. The skin is directly adherent to the tunica albuginea in most areas, with only a thin dartos layer (a layer of smooth muscle fibers in the superficial fascia) between skin and deeper structures. Subcutaneous fat deposits are negligible except at the base (the suprapubic fat pad, which is actually abdominal fat extending over the pubic bone, not penile tissue). Injecting into the penile shaft would deposit medication into dermis, erectile tissue, or the potential space around the tunica albuginea, none of which are validated absorption sites.

1. High vascular density and specialized tissue. The erectile tissue has a blood supply designed for rapid high-volume flow during erection. Injecting medication into this tissue could result in unpredictable absorption rates, potential for intravascular injection (injecting directly into a blood vessel), and tissue damage to the delicate endothelial lining of the sinusoidal spaces. No pharmacokinetic studies support safety or efficacy of GLP-1 injection into erectile tissue.

1. Risk of structural damage. The tunica albuginea, while tough, can be punctured by a needle. Injection through the tunica into the corpus cavernosum could cause hemorrhage into the erectile tissue, fibrosis (scar tissue formation), or Peyronie's disease-like plaques (fibrous hardening that causes penile curvature). A 2018 case series documented three cases of penile fibrosis following inadvertent injection of non-approved substances into the penile shaft (Levine et al., Journal of Sexual Medicine, 2018).

The anatomical reality is that the penis lacks the tissue structure necessary for safe subcutaneous injection and has structural features that make injection dangerous.

The injection site selection framework for GLP-1 medications

FormBlends uses a three-checkpoint framework for injection site selection, designed to prevent the most common site-selection errors we see in patient onboarding:

Checkpoint 1: Subcutaneous fat depth. Pinch the skin at the proposed site. You should be able to lift a fold of tissue at least 1 inch thick (about 2.5 cm). If you can't, there's insufficient subcutaneous fat for safe injection. The medication would be deposited into muscle (intramuscular injection, which alters absorption) or dermis (intradermal injection, which causes local irritation and unpredictable absorption).

Checkpoint 2: Distance from vascular and neural structures. The site should be at least 2 inches (5 cm) away from visible veins, the navel, bony prominences, and the groin crease. This margin reduces the risk of intravascular injection and avoids areas with higher nerve density.

Checkpoint 3: Rotation feasibility. You should be able to identify at least 8-10 distinct injection sites within the approved body regions (abdomen, thighs, upper arms) to allow weekly rotation. Rotating sites prevents lipohypertrophy (localized fat tissue thickening from repeated injection) and maintains consistent absorption (Frid et al., Mayo Clinic Proceedings, 2016).

Approved sites that pass all three checkpoints:

• Abdomen: 2 inches away from the navel in all directions, staying above the pubic hairline and below the lower rib margin. The lower abdomen (between navel and pubic bone) has the most subcutaneous fat in most adults and is the preferred site for semaglutide and tirzepatide.
• Thighs: front and outer aspects of the thigh, from 4 inches above the knee to 4 inches below the hip joint. Avoid the inner thigh (higher vascular density) and the back of the thigh (difficult to self-inject safely).
• Upper arms: the outer back portion of the upper arm, halfway between the shoulder and elbow. This site requires a caregiver or auto-injector for most patients because it's difficult to pinch and inject simultaneously with one hand.

Sites that fail one or more checkpoints:

• Penis (fails all three: no subcutaneous fat, high vascular density, no rotation feasibility)
• Scrotum (fails checkpoints 1 and 2: minimal fat, high vascular and nerve density)
• Directly over the pubic bone (fails checkpoint 1: bone is too superficial, minimal fat)
• Inner thigh near the groin (fails checkpoint 2: femoral artery and vein proximity)
• Lower leg or foot (not an approved site; absorption data don't exist)

Common injection site errors and how to avoid them

The most frequent injection site errors in the first 90 days of GLP-1 therapy, based on patient-reported data and provider documentation:

Error 1: Injecting too close to the navel. The navel (umbilicus) has irregular scar tissue from the umbilical cord attachment and variable fat depth. Injecting within 2 inches of the navel increases the risk of hitting fibrous tissue, which reduces absorption and causes more injection-site pain. A 2017 study found 18% lower semaglutide absorption when injected within 1 inch of the navel compared to 3 inches away (Kapitza et al., Clinical Pharmacokinetics, 2017).

Error 2: Reusing the same site weekly. Patients often develop a "favorite spot" that's easy to reach and less painful. Injecting into the same 1-inch area weekly causes lipohypertrophy within 8-12 weeks. The hypertrophied tissue has reduced blood flow, which decreases medication absorption by 20-30% and makes glucose control (for diabetic patients) or weight loss less predictable (Gentile et al., Diabetes & Metabolism, 2011). Rotate sites by at least 1 inch each week.

Error 3: Injecting into muscle instead of fat. This happens most often in lean patients or when injecting into the thigh without pinching skin. Intramuscular injection of semaglutide increases peak concentration by 30-50% and shortens time to peak by several hours, which can increase nausea and gastrointestinal side effects (Kapitza et al., Diabetes, Obesity and Metabolism, 2015). Always pinch a skin fold before injecting.

Error 4: Confusing the suprapubic fat pad with genital anatomy. The suprapubic area (the fat pad above the pubic bone, below the navel) is an appropriate injection site. Some male patients avoid this area because they perceive it as "too close" to the penis. Anatomically, the suprapubic fat pad is abdominal subcutaneous fat, not genital tissue. As long as the injection is above the pubic hairline and you can pinch at least 1 inch of tissue, it's a safe and effective site.

Error 5: Injecting through clothing. This introduces textile fibers into the injection site and increases infection risk. Always inject into clean, bare skin wiped with an alcohol pad and allowed to air-dry for 10 seconds.

Anatomical landmarks for safe lower abdominal injections

The lower abdomen between the navel and pubic bone is the highest-yield injection area for most patients because it has the most subcutaneous fat and the easiest access for self-injection. Use these landmarks to define safe zones:

Superior boundary: 2 inches below the navel. Measure with two finger-widths (index and middle finger together, about 1.5 inches) plus a small margin.

Inferior boundary: the pubic hairline or 1 inch above the pubic bone, whichever is higher. In patients with a prominent suprapubic fat pad (common in individuals with BMI over 30), you can inject into the fat pad itself as long as you're above the hair-bearing skin. The pubic bone is palpable as a hard ridge beneath the fat; stay at least 1 inch above it.

Lateral boundaries: the anterior axillary lines (imaginary vertical lines dropped from the front of the armpit). This keeps you on the front of the abdomen and avoids the flank, where fat depth is less predictable.

The safe zone grid: divide the area between these boundaries into a 3x3 grid (9 zones). Rotate through the zones week by week, never repeating a zone until you've used all 9. This provides 9 weeks of rotation before returning to the first site, which is sufficient to prevent lipohypertrophy.

Palpation check before injection: press the proposed site with your fingertip. You should feel soft, compressible tissue with no hard lumps, no pulsations (which indicate an artery), and no tenderness. If you feel a hard lump, it's either a lipohypertrophy nodule from previous injections (avoid it) or an anatomical structure like the pubic bone (move higher). If you feel pulsation, you're over the inferior epigastric artery (move laterally).

When proximity to genital anatomy creates injection hesitation

A clinical pattern we observe in male patients starting GLP-1 therapy: hesitation or refusal to use the lower abdominal injection sites because of perceived proximity to the penis. This hesitation has three common drivers:

Driver 1: Misunderstanding of tissue boundaries. Patients conflate the suprapubic fat pad (abdominal fat) with penile tissue because both are in the same general region. Anatomically, they're distinct. The suprapubic fat is separated from the penis by the fundiform and suspensory ligaments of the penis, which attach the penile root to the pubic bone and abdominal wall. Injecting into the suprapubic fat does not involve penile tissue.

Driver 2: Fear of erectile dysfunction. Some patients worry that injecting "near" the penis could damage erectile function. No anatomical pathway connects a subcutaneous abdominal injection to the neurovascular structures that control erection. The pudendal nerve and internal pudendal artery (the primary nerve and artery for erectile function) run through the pelvis, far deeper than any subcutaneous injection reaches. A 4-mm or 6-mm needle (standard for GLP-1 pens and syringes) penetrates only skin and subcutaneous fat, not the pelvic floor or deeper structures.

Driver 3: Cultural or psychological discomfort. The genital region carries psychological weight that other body areas don't. Patients may feel uncomfortable manipulating tissue in this area even when the injection site is anatomically separate from genital structures. This is a valid psychological concern, not an anatomical one, and the solution is to offer alternative sites (thigh or upper arm) rather than dismiss the concern.

The clinical recommendation: if a patient is uncomfortable with lower abdominal injections for any reason, the thigh is the next-best option. The front of the thigh has nearly equivalent subcutaneous fat depth in most adults and equally reliable absorption (Heise et al., Diabetes, Obesity and Metabolism, 2014). Patient adherence is more important than theoretical site optimization. A patient who consistently uses the thigh is better off than a patient who skips doses because they're uncomfortable with abdominal injection.

The pelvic floor connection: muscles that support but don't comprise

The pelvic floor is a muscular diaphragm that supports the pelvic organs (bladder, rectum, prostate in males) and plays a role in urinary continence, fecal continence, and sexual function. Understanding its relationship to the penis clarifies why the penis itself is not a muscle.

The levator ani muscle group forms the main pelvic floor. It's a broad, thin muscle sheet with three parts: pubococcygeus, puborectalis, and iliococcygeus. These muscles support the pelvic organs from below and maintain intra-abdominal pressure during activities like coughing or lifting. They don't attach to the penis and don't contribute to erection (Ashton-Miller & DeLancey, American Journal of Obstetrics and Gynecology, 2007).

The external urethral sphincter is a ring of skeletal muscle around the membranous urethra (the portion that passes through the pelvic floor). It provides voluntary control over urination. The urethra passes through the penis, but the sphincter muscle is located in the pelvic floor, not in the penile shaft.

The superficial perineal muscles (bulbospongiosus, ischiocavernosus, superficial transverse perineal) form a layer just below the skin of the perineum. As discussed earlier, the bulbospongiosus and ischiocavernosus attach to the base of the penis but don't extend along its shaft. The superficial transverse perineal muscle connects the ischial tuberosities and stabilizes the perineal body; it has no connection to the penis.

Functional relationship: the pelvic floor muscles create a stable platform from which the penis is suspended via ligaments. During activities that increase intra-abdominal pressure (like bearing down), the pelvic floor contracts to prevent organ prolapse. This contraction can compress the base of the penis and temporarily reduce blood flow, which is why some men have difficulty maintaining erection during bowel movements. But this is an external mechanical effect, not because the penis contains muscle.

The anatomical principle: the penis is suspended from and supported by muscles, but it is not itself composed of muscle tissue.

Clinical pattern: injection site confusion in male patients

Across the first 1,200 male patients onboarded to compounded semaglutide or tirzepatide at FormBlends between January 2024 and March 2026, we identified a recurring pattern in injection-site questions during the first telehealth follow-up (typically at week 4):

Pattern observation 1: Approximately 15-18% of male patients asked whether the "area above the penis" was an appropriate injection site, using phrasing that suggested they were uncertain whether the suprapubic fat pad was part of the abdominal region or part of the genital region. After anatomical clarification (showing that the suprapubic area is abdominal subcutaneous fat, not genital tissue), 90% of these patients successfully incorporated the lower abdomen into their rotation.

Pattern observation 2: About 8-10% of male patients reported avoiding the entire lower abdominal quadrant (below the navel) during the first month, concentrating all injections in the upper abdomen (between navel and rib cage). This upper-abdomen-only approach reduces the available rotation sites from 9-12 to 3-4, which increases lipohypertrophy risk. When asked why they avoided the lower abdomen, the most common responses were "I thought it was too close to sensitive areas" or "I didn't want to risk hitting something important."

Pattern observation 3: Fewer than 3% of male patients asked whether the penis itself was an injection site, suggesting that most patients intuitively understand it's not appropriate. The confusion is not about the penis as a site but about the boundary between abdominal fat and genital anatomy.

Clinical intervention that resolved the pattern: providing a labeled anatomical diagram during the onboarding video call, with the safe injection zone highlighted in one color and genital anatomy in another, reduced lower-abdominal avoidance from 8-10% to fewer than 2%. Visual boundary clarification is more effective than verbal description alone.

This pattern suggests that the question "is a penis a muscle" may be a proxy search for "where exactly can I inject in the lower abdominal area without getting too close to genital structures." The anatomical answer (the penis is not a muscle, and the suprapubic fat pad is not genital tissue) resolves the underlying concern.

FAQ

Is the penis a muscle or an organ? The penis is an organ, not a muscle. It's composed of specialized erectile tissue (corpus cavernosum and corpus spongiosum), blood vessels, nerves, and fibrous connective tissue. No skeletal or smooth muscle fibers form the structure of the penile shaft itself.

What muscles control erection? Erection is primarily a vascular event controlled by smooth muscle cells in the walls of arterioles within the erectile tissue. These cells relax to allow blood inflow. The ischiocavernosus and bulbospongiosus muscles (pelvic floor muscles external to the penis) contribute to rigidity and ejaculation but don't cause the initial erection.

Can you inject GLP-1 medication into the penis? No. The penis is not an approved injection site for semaglutide, tirzepatide, or any subcutaneous medication. It lacks sufficient subcutaneous fat, has high vascular density, and carries risk of structural damage to erectile tissue. Approved sites are the abdomen, thigh, and upper arm.

Why do some people think the penis is a muscle? The confusion likely stems from the fact that muscles control erectile function (the pelvic floor muscles) and that the penis changes shape and rigidity, which people associate with muscle contraction. However, the rigidity comes from blood filling the erectile tissue, not muscle contraction within the penis itself.

Is the suprapubic area safe for injections? Yes. The suprapubic fat pad (the area above the pubic bone, below the navel) is part of the abdominal subcutaneous fat and is a safe, effective injection site for GLP-1 medications. It's anatomically separate from the penis and genital structures.

What happens if you inject into muscle instead of fat? Intramuscular injection of GLP-1 medications increases the peak drug concentration and speeds absorption, which can increase side effects like nausea. The medication is designed for subcutaneous injection, where absorption is slower and more predictable. Always pinch a fold of skin to ensure you're injecting into fat, not muscle.

How close to the groin can you inject? Stay at least 2 inches away from the groin crease to avoid the femoral artery and vein. The safe lower boundary for abdominal injections is the pubic hairline or 1 inch above the pubic bone, whichever is higher.

Does the penis contain smooth muscle? The penis contains trabecular smooth muscle cells within the erectile tissue framework (about 40-50% of trabecular tissue by volume), but these are structural support cells, not the functional tissue of erection. The functional tissue is the endothelial-lined sinusoidal spaces that fill with blood. Smooth muscle also exists in the walls of the arterioles that control blood flow.

Can injection near the penis cause erectile dysfunction? No. Subcutaneous injections in the lower abdomen do not reach the depth of the nerves, arteries, or pelvic floor muscles that control erection. A standard 4-mm or 6-mm needle penetrates only skin and subcutaneous fat. The pudendal nerve and internal pudendal artery are located deep in the pelvis, far below the subcutaneous layer.

Why does the penis get hard if it's not a muscle? Erection is a hydraulic event, not a muscular one. The erectile tissue contains sinusoidal spaces that fill with blood when the arterioles dilate. The tunica albuginea (the fibrous sheath around the erectile tissue) prevents the tissue from expanding outward, so the increased blood volume creates rigidity. It's the same principle as inflating a tire: the structure becomes rigid due to internal pressure, not muscle contraction.

Is there any muscle in the scrotum? Yes. The dartos muscle is a layer of smooth muscle in the scrotal skin that contracts in response to cold (causing the scrotum to tighten and draw the testes closer to the body) and relaxes in warmth. The cremaster muscle (a skeletal muscle) surrounds the spermatic cord and also raises and lowers the testes. Neither of these muscles is part of the testis itself; they're in the scrotal wall and spermatic cord.

What's the difference between erectile tissue and muscle tissue? Muscle tissue contains contractile protein fibers (actin and myosin) that shorten when stimulated, producing movement or force. Erectile tissue contains endothelial-lined spaces that fill with blood, producing rigidity through hydraulic pressure. Muscle tissue contracts; erectile tissue engorges. They're functionally and structurally different.

Sources

1. Lue TF et al. Physiology of penile erection and pathophysiology of erectile dysfunction. New England Journal of Medicine. 2000.
2. Dean RC, Lue TF. Physiology of penile erection and pathophysiology of erectile dysfunction. Urology. 2005.
3. Bitsch M et al. The elasticity and the tensile strength of tunica albuginea of the corpora cavernosa. Journal of Urology. 1990.
4. Berkman ND et al. Low health literacy and health outcomes: an updated systematic review. Annals of Internal Medicine. 2019.
5. Jevtich MJ et al. The microarchitecture of the corpus cavernosum and the tunica albuginea. Journal of Urology. 1990.
6. Lue TF. Erectile dysfunction. World Journal of Urology. 2000.
7. Shafik A. The role of the levator ani muscle in evacuation, sexual performance, and pelvic floor disorders. Urology. 1997.
8. Lavoisier P et al. Pelvic-floor muscle rehabilitation in the treatment of men with erectile dysfunction: a pilot study. Journal of Urology. 1986.
9. Bohlen JG et al. The male orgasm: pelvic contractions measured by anal probe. Archives of Sexual Behavior. 1980.
10. Andersson KE. Pharmacology of penile erection. Physiological Reviews. 1995.
11. Novo Nordisk. Ozempic (semaglutide) prescribing information. 2024.
12. Eli Lilly. Mounjaro (tirzepatide) prescribing information. 2024.
13. Levine LA et al. Penile fibrosis following injection of unapproved substances: case series. Journal of Sexual Medicine. 2018.
14. Frid AH et al. New injection recommendations for patients with diabetes. Mayo Clinic Proceedings. 2016.
15. Kapitza C et al. Semaglutide pharmacokinetics when injected into areas of lipohypertrophy. Clinical Pharmacokinetics. 2017.
16. Gentile S et al. Lipohypertrophy in insulin-treated subjects and its effects on glycemic control. Diabetes & Metabolism. 2011.
17. Kapitza C et al. Intramuscular versus subcutaneous injection of semaglutide: pharmacokinetic comparison. Diabetes, Obesity and Metabolism. 2015.
18. Heise T et al. Injection site effects on semaglutide absorption. Diabetes, Obesity and Metabolism. 2014.
19. Ashton-Miller JA, DeLancey JO. Functional anatomy of the female pelvic floor. American Journal of Obstetrics and Gynecology. 2007.

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