Vas-occlusive contraception

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A diagram of the mechanism of action of vas-occlusive contraceptive methods. Vas-occlusive Contraception Diagram.svg
A diagram of the mechanism of action of vas-occlusive contraceptive methods.

Vas-occlusive contraception is a form of male contraception that blocks sperm transport in the vas deferens, the tubes that carry sperm from the epididymis to the ejaculatory ducts.

Contents

Various vas-occlusive contraceptive methods have been researched for human-use, with interest in both reversible and irreversible methods, with the purpose of finding a suitable alternative to vasectomy and possible hormonal contraceptive treatments that are currently being researched. [1] [2] [3] [4] Potential methods include clips, plugs, valves, polymers, hydrogels, and other devices.

Types

There are numerous vas-occlusive contraceptive methods and devices that have been researched. Outlined here are a few main categories and descriptions.

Intravasal control valve (ICV)

An intravasal control valve is a reversible valve implanted in the vas deferens with the ability to either inhibit or permit sperm passage depending on the position of the device. Bionyx has developed a T-shaped intravasal control valve composed of gold and stainless steel for use in humans. [5] Through rotation, a perforated ball within the T can be used to obstruct sperm flow or allow sperm flow. [6] Skilled microsurgery is required for the ICV implant.

Chemosterilization

Injection of non-toxic and sclerotic chemicals in the vas deferens can result in blockage of sperm transport due to scarring on the vas deferens wall. At least 26 different chemical combinations have been attempted to achieve sterilization. [6] A combination of carbolic and n-butyl alpha cyanoacrylate has resulted in complete blockage of the vas deferens through adhesion to the luminal surface. This chemical combination resulted in a 96% azoospermia and a 99% pregnancy prevention eight years follow injection in humans. [6] The scar tissue created is not always compact and successful in occluding the vas deferens, which results in the 4% azoospermia failure rate. [6] The injection of the chemical combination of ethanol and formaldehyde also resulted in sterility in humans. [6] However, these chemical combinations are irreversible.

Vas-occlusive plugs

There are two types of vas-occlusive plugs: injectable plugs and non-injectable plugs. Injection of medical polyurethane (MPU) to form a plug in the vas deferens resulted in azoospermia in 96% of men, though these result were seen 24 months after injection. [6] [7] [8] Studies on over 130 men following removal of the plug within five years showed successful restoration of fertility. [6] The Shug, short for "silicon plug", is an example of a non-injectable plug, though there is little to no research on the Shug following 2008. [8] The Shug is composed of two silicon plugs with accompanying nylon tails that attach to the vas deferens wall. It is surgically inserted into the vas deferens and must also be removed surgically. Shug human trials showed a 97% decrease in sperm motility through the vas deferens. [6] However, plugs have been shown to have a lower efficacy rate when compared to traditional vasectomy overall. [3]

Intravasal thread (IVT)

Insertion of an intravasal thread (IVT), also known as an intravasal device (IVD), in the vas deferens has been shown to inhibit sperm transport via mechanical obstruction and the removal of the IVT results in restored vas deferens patency. [6] However, this method has differential species-specific results: in pigs, a plastic IVT had no significant effect on sperm count; in dogs, a plastic and polyethylene IVT consistently blocked sperm transport during the experimental period and removal of the device restored sperm transport after a period of two weeks; and in human subjects, a urethane-coated nylon IVT resulted in significantly reduced sperm count but could not guarantee absolute sterility at the same rate as a vasectomy. [6] [3]

RISUG

Reversible inhibition of sperm under guidance (RISUG) is a non-toxic polymer gel-based contraceptive that is injected into the lumen of the vas deferens and results in infertility within 10 days following injection. [7] RISUG is composed of styrene maleic anhydride (SMA) dissolved in dimethyl sulfoxide (dimethyl sulfoxide), [6] which is believed to both partially occlude the vas deferens by coating the inner walls of the vas deferens with the polymer chemical, while also deactivating the sperm that are able to pass through the partially occluded vas deferens, thereby preventing successful fertilization. [7] The exact mechanism of the deactivation effect on sperm is still unknown. [3] [7] RISUG inhibits sperm transport but allows fluid to pass through, which prevents pressure from building up in the vas deferens. [7] RISUG has been shown successful in previous human clinical trials in India and is currently undergoing Phase III clinical trials. [7] [9] [5]

Vasalgel

Vasalgel was inspired by RISUG and created by the Parsemus Foundation in order to be used outside of India. [9] Vasalgel is composed of 25% styrene-alt-maleic acid (SMA acid) dissolved in dimethyl sulfoxide. [9] The major difference between RISUG and Vasalgel is that Vasalgel is composed of SMA acid without SMA anhydride, which allows for a longer shelf-life, smaller probability of hydrolysis to an acid, and less complex production process. [9] Vasalgel was successful in achieving azoospermia in rabbits within 36 days of injection, as well as returned vas deferens patency. [9] In 2023, the patent for Vasalgel was acquired by NEXT Life Sciences, Inc., which plans to bring the technology to market under the name Plan A for Men. [10]

ADAM

Contraline, Inc. is developing a vas-occlusive medical device known as ADAM. ADAM is an injectable hydrogel designed specifically for the dynamic environment of the vas deferens. Unlike RISUG and Vasalgel, which require injection in organic solvent, ADAM is aqueous-based. The ADAM hydrogel is inserted through a minimally-invasive, outpatient procedure. The company has made advancements in percutaneous (non-surgical) delivery of vas-occlusive devices using ultrasound guidance. Clinical trials on ADAM began in 2022. [11]

Side effects

Vas-occlusive contraception methods are expected to have similar side effects to vasectomy, which is generally regarded as a safe and low-risk procedure.

See also

Related Research Articles

<span class="mw-page-title-main">Vasectomy</span> Surgical procedure for male sterilization

Vasectomy is an elective surgical procedure that results in male sterilization, often as a means of permanent contraception. During the procedure, the male vasa deferentia are cut and tied or sealed so as to prevent sperm from entering into the urethra and thereby prevent fertilization of a female through sexual intercourse. Vasectomies are usually performed in a physician's office, medical clinic, or, when performed on a non-human animal, in a veterinary clinic. Hospitalization is not normally required as the procedure is not complicated, the incisions are small, and the necessary equipment routine.

Sterilization is any of a number of medical methods of permanent birth control that intentionally leaves a person unable to reproduce. Sterilization methods include both surgical and non-surgical options for both males and females. Sterilization procedures are intended to be permanent; reversal is generally difficult.

<span class="mw-page-title-main">Intracytoplasmic sperm injection</span> In vitro fertilization procedure

Intracytoplasmic sperm injection is an in vitro fertilization (IVF) procedure in which a single sperm cell is injected directly into the cytoplasm of an egg. This technique is used in order to prepare the gametes for the obtention of embryos that may be transferred to a maternal uterus. With this method, the acrosome reaction is skipped.

<span class="mw-page-title-main">Epididymis</span> Tube that connects a testicle to a vas deferens

The epididymis is an elongated tubular genital organ attached to the posterior side of each one of the two male reproductive glands, the testicles. It is a single, narrow, tightly coiled tube in adult humans, 6 to 7 centimetres in length; uncoiled the tube would be approximately 6 m long. It connects the testicle to the vas deferens in the male reproductive system. The epididymis serves as an interconnection between the multiple efferent ducts at the rear of a testicle (proximally), and the vas deferens (distally). Its primary function is the storage, maturation and transport of sperm cells.

<span class="mw-page-title-main">Vas deferens</span> Part of the male reproductive system of many vertebrates

The vas deferens, ductus deferens, or sperm duct is part of the male reproductive system of many vertebrates. The vasa deferentia are paired sex organs that transport sperm from the epididymides to the ejaculatory ducts in anticipation of ejaculation. The vas deferens is a partially coiled tube which exits the abdominal cavity through the inguinal canal.

<span class="mw-page-title-main">Ejaculatory duct</span> Male anatomical structures

The ejaculatory ducts are paired structures in the male reproductive system. Each ejaculatory duct is formed by the union of the vas deferens with the duct of the seminal vesicle. They pass through the prostate, and open into the urethra above the seminal colliculus. During ejaculation, semen passes through the prostate gland, enters the urethra and exits the body via the urinary meatus.

<span class="mw-page-title-main">Azoospermia</span> Medical condition of a man whose semen contains no sperm

Azoospermia is the medical condition of a man whose semen contains no sperm. It is associated with male infertility, but many forms are amenable to medical treatment. In humans, azoospermia affects about 1% of the male population and may be seen in up to 20% of male infertility situations in Canada.

<span class="mw-page-title-main">Reversible inhibition of sperm under guidance</span>

Reversible inhibition of sperm under guidance (RISUG), formerly referred to as the synthetic polymer styrene maleic anhydride (SMA), is the development name of a male contraceptive injection developed at IIT Kharagpur in India by the team of Dr. Sujoy K. Guha.

Male contraceptives, also known as male birth control, are methods of preventing pregnancy by interrupting the function of sperm. The main forms of male contraception available today are condoms, vasectomy, and withdrawal, which together represented 20% of global contraceptive use in 2019. New forms of male contraception are in clinical and preclinical stages of research and development, but as of 2024, none have reached regulatory approval for widespread use.

Terms oligospermia, oligozoospermia, and low sperm count refer to semen with a low concentration of sperm and is a common finding in male infertility. Often semen with a decreased sperm concentration may also show significant abnormalities in sperm morphology and motility. There has been interest in replacing the descriptive terms used in semen analysis with more quantitative information.

An alternative male contraceptive method involves heating the testicles so that they cannot produce sperm. Sperm are best produced at a temperature slightly below body temperature. The muscles around a male's scrotum involuntarily tighten if the man's body temperature drops, and they loosen, allowing the testes to hang, if the body temperature rises. This is the body's way of keeping the sperm at an ideal temperature. This means that sperm production can be disrupted with increased temperature. Some suggest exposure to high temperatures can affect fertility for months.

Congenital absence of the vas deferens (CAVD) is a condition in which the vasa deferentia reproductive organs fail to form properly prior to birth. It may either be unilateral (CUAVD) or bilateral (CBAVD).

<span class="mw-page-title-main">Testicular sperm extraction</span> Surgical procedure

Testicular sperm extraction (TESE) is a surgical procedure in which a small portion of tissue is removed from the testicle and any viable sperm cells from that tissue are extracted for use in further procedures, most commonly intracytoplasmic sperm injection (ICSI) as part of in vitro fertilisation (IVF). TESE is often recommended to patients who cannot produce sperm by ejaculation due to azoospermia.

<span class="mw-page-title-main">Comparison of birth control methods</span>

There are many methods of birth control that vary in requirements, side effects, and effectiveness. As the technology, education, and awareness about contraception has evolved, new contraception methods have been theorized and put in application. Although no method of birth control is ideal for every user, some methods remain more effective, affordable or intrusive than others. Outlined here are the different types of barrier methods, hormonal methods, various methods including spermicides, emergency contraceptives, and surgical methods and a comparison between them.

<span class="mw-page-title-main">Sperm granuloma</span> Lump of extravasated sperm found in some vasectomized men

A sperm granuloma is a lump of leaked sperm that appears along the vasa deferentia or epididymides in vasectomized individuals. While the majority of sperm granulomas are present along the vas deferens, the rest of them form at the epididymis. Sperm granulomas range in size, from one millimeter to one centimeter. They consist of a central mass of degenerating sperm surrounded by tissue containing blood vessels and immune system cells. Sperm granulomas may also have a yellow, white, or cream colored center when cut open. While some sperm granulomas can be painful, most of them are painless and asymptomatic. Sperm granulomas can appear as a result of surgery, trauma, or an infection. They can appear as early as four days after surgery and fully formed ones can appear as late as 208 days later.

<span class="mw-page-title-main">Contraceptive implant</span> Implantable medical device used for birth control

A contraceptive implant is an implantable medical device used for the purpose of birth control. The implant may depend on the timed release of hormones to hinder ovulation or sperm development, the ability of copper to act as a natural spermicide within the uterus, or it may work using a non-hormonal, physical blocking mechanism. As with other contraceptives, a contraceptive implant is designed to prevent pregnancy, but it does not protect against sexually transmitted infections.

<span class="mw-page-title-main">Birth control</span> Method of preventing human pregnancy

Birth control, also known as contraception, anticonception, and fertility control, is the use of methods or devices to prevent unintended pregnancy. Birth control has been used since ancient times, but effective and safe methods of birth control only became available in the 20th century. Planning, making available, and using human birth control is called family planning. Some cultures limit or discourage access to birth control because they consider it to be morally, religiously, or politically undesirable.

Vasectomy reversal is a term used for surgical procedures that reconnect the male reproductive tract after interruption by a vasectomy. Two procedures are possible at the time of vasectomy reversal: vasovasostomy and vasoepididymostomy. Although vasectomy is considered a permanent form of contraception, advances in microsurgery have improved the success of vasectomy reversal procedures. The procedures remain technically demanding and may not restore the pre-vasectomy condition.

The Parsemus Foundation is an American non-governmental organization whose objective is to advance low-cost evidence-based medicines not pursued by the pharmaceutical industry. The foundation's focus is on supporting small proof-of-concept studies and then pursuing press coverage of the results, so that the advances change treatment practice rather than disappearing into the scientific literature. Many of the studies supported involve low-cost approaches that are not under patent.

No-scalpel vasectomy is a type of vasectomy procedure in which a specifically designed ringed clamp and dissecting hemostat is used to puncture the scrotum to access the vas deferens. This is different from a conventional or incisional vasectomy where the scrotal opening is made with a scalpel. The NSV approach offers several benefits, including lower risk for bleeding, bruising, infection, and pain. The NSV approach also has a shorter procedure time than the conventional scalpel incision technique. Both approaches to vasectomy are equally effective. Because of the inherent simplicity of the procedure it affords itself to be used in public health programs worldwide. This method is used in over 40 countries for male sterilisation.

References

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  9. 1 2 3 4 5 Waller, D; Bolick, D; Lissner, E; Premanandan, C; Gamerman, G (2016). "Azoospermia in rabbits following an intravas injection of Vasalgel". Basic and Clinical Andrology. 26: 6. doi: 10.1186/s12610-016-0033-8 . PMC   4812607 . PMID   27030808.
  10. Hobbins, Katie (2023-08-22). "'Plan A' Offers a New Option in Male Birth Control". www.mddionline.com.
  11. "Contraline".

Further reading