Beta Blockers and Nicotinic Acid Ionic Liquids for Transdermal Drug Delivery
Cardiovascular disease effects approximately 50 million people in the United States.1 Diagnosis of cardiovascular disease is characterized by high blood pressure which leads to problems such as a myocardial infarction, stroke, and/or death.1 Initial treatment to decrease blood pressure and associated risks consists of lifestyle changes like exercise and dietary changes, but if the patient’s blood pressure is not improved, medications are considered for treatment.1 Beta blockers are a medication used for treatment of high blood pressure and is also prescribed post-myocardial infarction.1,2 Niacin is a vitamin used as a treatment to improve HDL cholesterol and reduce atherosclerosis. 3,4 These are drugs that are both delivered orally, but there are limitations to oral drug delivery.
Oral drug delivery involves the transport of a liquid or pill, taken by mouth, into the stomach.5 The stomach absorbs the drug which then passes through the liver, decreasing the amount of drug that is delivered to the target area.5 The passage of the drug through the liver, can also result in liver damage, because of the toxicity of the drug.3 Additional side effects associated with medications include gastrointestinal problems and skin flushing.3 Another limitation to oral drug delivery is patient compliance. Niacin and beta blocker medications are prescribed to be taken twice daily.1,2 It is because of the need for a strict routine to take the medication, that patient compliance may be low. A study on patient compliance was conducted, and it was concluded that patients are not good at complying to the doctor’s instructions and compliance must be improved to see results of the treatment.2 Given the limitations and potential side effects of oral drug delivery of treatments for cardiovascular disease, an alternative could be the delivery of the drug through the skin.
Transdermal drug delivery delivers a drug by patch, gel, or cream, and provides a more targeted route for the blood to enter the blood stream.6 An example is the nicotine patch for smoking cessation, which delivers nicotine into the blood stream.6 Benefits of transdermal drug delivery are that it is not painful, does not cause liver damage, and they can be used for up to a week to increase patient compliance.6 Also transdermal drug delivery allows for more targeted delivery. Previous experiments that were conducted, showed that non-steroidal anti-inflammatory drugs can be delivered to the targeted to area to treat inflammation without the side effects of the oral medication. The limitation to transdermal drug delivery is the small amount of drug delivered, because the stratum corneum, the upper most layer of the skin, limits the transport of the drug through the skin.7 An alternative transdermal method, would enhance the permeability of the drug, and allow the drug to pass through stratum corneum at a faster rate. It is also important that this drug passes through all layers of the skin, because the goal is to get it into the blood stream. The most effective transdermal delivery systems have small molecular weights and often utilize penetration enhancers to improve the delivery through the skin.6 It is necessary to improve the drug delivery system, that a transdermal drug can penetrate the skin and deliver the drug to the targeted area. Beta-blockers have been considered for transdermal drug delivery, because more drug is delivered and it would increase patient compliance.8 There have not been studies done on transdermal drug delivery of niacin for the purposes of treating cardiovascular complications.
Ionic liquids are an option for transdermal delivery systems.7 Ionic liquids increase the solubility of active pharmaceutical ingredients, the stability and bioavailability of the drug, and its physicochemical properties can be changed.9 Ionic liquids are synthesized in a metathesis reaction, where an anion and cation are paired in a solvent.10 Specifically, room temperature ionic liquids are of interest, because they are liquid at room temperature and would be ideal if a gel or cream were to be developed.10 Ionic liquids can be synthesized to serve as a solvent for an insoluble or slightly soluble drug, like niacin, which has low solubility in methanol, acetonitrile, and other solvents.9,11 In an experiment where ionic liquids were serving as a solvent, the presence of the ionic liquid increased the drug’s penetration into the skin layers.7 Ionic liquids can also be synthesized using the pharmaceutical salt as an anion or cation to serve as the active pharmaceutical ingredient in the metathesis reaction.9 This would allow for more drug to be delivered, because the drug now makes up 50% of the total compound, as compared to current formulations. Ionic liquids can be synthesized where the anion and cation pairs can be changed to treat a side effect associated with a drug.12 For example, niacin produces a flushing effect that can be treated with laropiprant.3 Pairing niacin with laropiprant to create an ionic liquid could possibly reduce the side effect of flushing. The characteristics of ionic liquids show a promising method of improving transdermal drug delivery systems to deliver a drug to the bloodstream.
With increasing prevalence of cardiovascular disease, treatments need to be created that support patient lifestyles and ensure they are maintaining their health. The creation of a transdermal drug delivery system to deliver niacin or beta-blockers into the blood stream, will help improve patient compliance, reduce the side effects associated with oral drug delivery systems, and ideally increase the amount of drug delivered. Research will need to be done on the ability of synthesized room-temperature ionic liquids consisting of niacin or beta-blockers to penetrate the skin and deliver drug to the targeted area.
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