The active ingredient oxybutynin belongs to the anticholinergics. It has a structural relationship to the alkaloid atropine.
What is oxybutynin?
Oxybutynin is used to treat strong urination or nocturnal enuresis. Oxybutynin is classified in the group of anticholinergics or parasympatholytics. The drug is used for the treatment of strong urge to urinate or nocturnal enuresis. It relaxes the smooth bladder muscles and reduces the urge to urinate, so that the patient does not have to empty his bladder as frequently. Oxybutynin has been used in Europe since the late 1980s. Since 2007, transdermal patches have been available in addition to tablets. In the U.S., there are also dosage forms available that are not approved in Europe. These are gels that the patient applies to the skin, allowing the active ingredient to enter the bloodstream. Structurally, oxybutynin is a racemate related to atropine. In the drugs, the tertiary amine occurs as oxybutynin hydrochloride or oxybutynin. Oxybutynin hydrochloride refers to a crystalline, whitish powder that dissolves readily in water.
Pharmacological action
Oxybutynin belongs to the group of drugs called spasmolytics, which exert an antispasmodic effect. The drug is able to act on both muscles and nerves. Thus, the body’s own neurotransmitter acetylcholine is displaced from its receptors, which are located on the parasympathetic nervous system. The parasympathetic nervous system belongs to the main nerves of the autonomic nervous system. Inhibition of muscarinic M-acetylcholine receptors results in relaxation of bladder smooth muscle. This effect causes the excessive tension of the bladder muscles to subside. In this way, the urinary bladder acquires more capacity. As a result, the patient feels less urge to urinate and suffers less frequently from uncontrolled urine leakage. Furthermore, oxybutynin inhibits sweat gland secretion.
Medical use and application
Oxybutynin is mainly used against different forms of urinary incontinence. In this case, the affected individuals primarily suffer from the excessive tightening of the urinary bladder muscle, which is mostly noticeable during the night hours. In addition, involuntary leakage of urine may occur. Other indications for oxybutynin are nocturnal enuresis, spastic neurogenic bladder, hypersensitivity of the bladder wall muscles due to neurogenic disorders, and unstable bladder in women. There are also indications for oxybutynin that have not yet been fully approved. For example, the anticholinergic is also administered off-label for hyperhidrosis (excessive sweating). However, this area of application is not approved in all European countries. In most cases, oxybutynin is taken in tablet form. The recommended dose in the initial stage is three times half a tablet per day. In the further course of treatment, the daily dose is half a tablet to one tablet. Later, the lowest dosage is considered recommended. If necessary, the dose can be increased to four times a tablet a day. Children over the age of five can also take oxybutynin. In this case, the recommended daily dose is two times half a tablet.
Risks and side effects
In some patients, the use of oxybutynin results in unwanted side effects. However, these do not show up in every person. In most cases, affected individuals experience constipation, dry mouth, accelerated heart rate, heat buildup, cardiac arrhythmias, palpitations, extensive swelling of the skin and mucous membranes, facial swelling, fatigue, dizziness, urinary retention, skin rashes, impotence, nausea, vomiting, and loss of appetite. Furthermore, blurred vision, sensitivity to light, dilation of the pupils, decrease in lacrimation, discomfort during urination, headache and allergic skin reactions are possible. In rare cases, anxiety disorders at night or confusion also appear. With permanent use of oxybutynin there is a risk of gum disease, caries or yeast infection in the oral cavity. It is not advisable to administer oxybutynin if the patient suffers from hypersensitivity to the drug.Other contraindications include urinary obstruction due to urethral stricture or benign enlargement of the prostate (prostate gland), urinary urgency and nocturnal urination due to kidney weakness or cardiac insufficiency, gastrointestinal disorders, intestinal obstruction (ileus) or ulcers of the colon. Oxybutynin is not recommended to be used during pregnancy and breastfeeding. The drug is not suitable for children under five years of age. Some interactions with other drugs should also be noted. For example, the effect of oxybutynin is increased when other anticholinergics or anti-parkinsonian drugs such as amantadine are taken at the same time. The same applies to atropine, neuroleptics such as butyrophenones or phenothiazines, quinidine, H1 antihistamines, and tricyclic antidepressants. Prolongation of oxybutynin action is possible with the use of antifungals such as itraconazole or ketoconazole and macrolide antibiotics such as erythromycin.
