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Erectile Dysfunction

Erectile dysfunction (ED) is characterised as the inability to obtain and/or maintain an erection sufficient for sexual intercourse. Approximately 398 million men age worldwide suffer from ED and is expected to grow to 446 million by 2026. This growth is driven by the high incidence of chronic diseases, including hypertension, diabetes and neurogenic and psychological disorder. This market was valued at US$4.82 billion in 2017 and is expected to grow to US$7.1 billion by 2026. The largest licensing agreement in the last five years was US$172 million for an oral prostaglandins (Spedra) ED treatment.

Indirect ED Treatments

Current first-line ED treatments include phosphodiesterase inhibitors such as Viagra and Cialis. Positive outcomes range from 36-76% of patients using Viagra to 11-47% using Cialis. Limitations of oral phosphodiesterase inhibitors treatments include:

  • Phosphodiesterase inhibitors are bitter to taste and therefore require coating thereby reducing their gastrointestinal absorption;

  • Bioavailability via the oral route is significantly affected by adverse conditions in the gastrointestinal pathway and metabolism by the liver (first-pass metabolism);

  • Oral absorption is significantly affected by food; fatty meals will significantly delay affects;

  • To overcome the low bioavailability and metabolism via the oral route and achieve an effective outcome (ie erection) a sufficiently high volume of drug must be taken achieve sufficient systemic levels of the active agent. These high systematic levels increase the likelihood of adverse events. Noted adverse events associated with Viagra and Cialis include vision loss, hearing loss, headache and nausea. Additiay, high systemic levels mean that these drugs are contraindicated for use in patients taking nitrates for heart conditions, certain antibiotics and H2 antagonists for treating reflux. Patients with existing kidney, liver or blood disorders are also advised not to take oral phosphodiesterase inhibitors.

  • Oral ED treatments have proven ineffective in treatment of prostatectomy patients.

  • One of the most cited problems mentioned by users of oral phosphodiesterase inhibitors is the time lag of between oral administration and activity, which significantly affects sexual spontaneity.

Direct ED Treatments

The only available alternate method of ED treatment is direct administration of active agents to the penis. The benefits of this method include the lower effective dose required for an effective outcome. This reduces the potential for adverse events. Additionally, this method of treatment allows the use of active agents in patients who would normally not use oral methods of treatments due to contraindications. Direct treatment protocols have also proven to be effective in patients who have had a prostatectomy.


Existing direct administration requires by injection of active agents into the intercavernosal cavities of the penis. Additional methods of treatment include insertion of active agents into the urethra. Both of these methods have significant adverse events including:

  • Injection site reactions (mild/moderate pain, irritation, bruising or slight bleeding);

  • Painful erection;

  • Penile discharge;

  • Pain/blending during urination/ejaculation;

  • Pain in penis/urethra/testicles;

  • Inability to self-inject; and

  • Lack of sexual spontaneity.

Method for direct administration of prostaglandins E1 into the penis for direct ED treatment.