Can minoxidil cause heart palpitations?
Yes. Minoxidil is associated with many cardiovascular effects. One of them is an increase in heart rate, which can potentially lead to a sensation of heart palpitations.
A regular dosage of minoxidil can increase the heartbeat by 3 to 5 beats per minute (bpm) [1]. A large dose of minoxidil increases the risk of tachycardia, which can increase the heartbeat to 120bpm or even 190 bpm for many hours [2].
However, those cases apply only to oral administration, where there is systemic exposure to the substance. In cases of topical application, the risk of such a complication is unlikely to occur due to the lower concentration.
What is minoxidil?
Minoxidil was initially introduced as an oral drug to treat high blood pressure. One of its noticed side effects was increased growth of body hair. This led to the development of many generic topical formulations for the treatment of androgenic alopecia. Because of this, it is currently more known for its ability to slow down or stop hair loss and promote its regrowth. [3, 4].
Minoxidil belongs to peripheral vasodilators. This class of medications works by relaxing and enlarging the small blood vessels in the peripheries. The dilation of the vessel creates additional space for the blood, so the blood pressure decreases. Minoxidil is used as part of a combination therapy with other drugs used to treat high blood pressure or with drugs that reduce its side effects [5].
As an over-the-counter drug against hair loss, minoxidil works greatly as a hair follicle stimulator. The therapeutic effect on hair regrowth is demonstrated for androgenetic alopecia in males and females. However, patients with severe alopecia areata respond poorly to topical minoxidil treatment [6].
How does Minoxidil work?
Minoxidil works through several mechanisms to stimulate hair growth. One of the primary ways is by acting on androgenic receptors (AR). It not only interacts with these receptors but also targets two other components: steroid 17-alpha-hydroxylase/17,20 lyase (CYP17A1) and aromatase (CYP19A1) [7].
Suppression of the expression of AR and CYP17A1 while boosting the activity of CYP19A1 leads to a decrease in the formation and binding of dihydrotestosterone. This hormone contributes to hair loss. It sticks around the follicle and restrains it from the nutrient supply, making it die [7].
Another significant action of minoxidil is its effect on the enzyme 5α-reductase type 2 (5α-R2). It downregulates the 5α-R2 gene expression in human keratinocyte cells, indicating an antiandrogenic effect [8].
Minoxidil also affects the growth cycle of hair follicles. It shortens the resting phase, accelerates the transition phase, and causes resting hair follicles to enter the growth phase prematurely. It also enhances the size of hair follicles [9].
Furthermore, minoxidil activates the kinase Akt and the mitogenic signaling molecule ERK. Both components are proliferative in the cell cycle and positively impact the survival of the cell. They also suppress the apoptotic Blc-2 and Bax, which allows the cell to keep living longer. The cells that are especially under this beneficial influence are the dermal papilla cells (DPCs) of the human hair follicle. This indicates that minoxidil stimulates hair growth by prolonging the growth phase through these proliferative and anti-apoptotic effects on DPCs [10].
How does the minoxidil influence the heart?
Minoxidil, a potent arteriolar vasodilator, can lead to several changes in cardiac structure and function.
One of the important effects of minoxidil on the heart is the induction of cardiac hypertrophy (increased size of the cardiac muscle). Treatment with this potent vasodilator can cause enlargement of the left and right ventricles, as well as the interventricular septum [11].
Because minoxidil dilates the peripheral vessels, it also influences myocardial hemodynamics and regional blood flow. It increases the mean right atrial and left ventricular end-diastolic pressures. Because of the reduced systemic and pulmonary vascular resistance and the drop in blood pressure, the cardiac output increases [12]. This causes the heart to overreact and adjust its muscle structure to better work in these conditions. Simply put, that is the reason for the increase in the cardiac muscle. However, it may result in insufficient subendocardial perfusion, which might lead to myocardial damage [13].
In some cases, minoxidil has led to myocardial hemorrhages and left ventricular papillary muscle necrosis [14]. It can also cause pericardial effusion, leading to cardiac tamponade [15]. In this condition, fluid gathers in the pericardial sac, a protective, thin membranous sac around the heart. The collected fluid increases the pressure around the heart, impairing the dilation to such an extent that the heart fails its role and the circulation of blood stops.
Despite these potential dangers, minoxidil has been found to improve ischemia-induced myocardial mechanical dysfunction. It enhanced the recovery of myocardial contraction after ischemia [16].
Is minoxidil safe in cardiovascular disease?
The safety of minoxidil in patients with cardiovascular disease is a topic of ongoing discussion.
The medication has been associated with several cardiovascular complications, including ischemic heart disease, left ventricular hypertrophy, pleural effusions, and pericardial effusions [17]. It can be problematic for some patients, as it can also cause an increase in heart rate and fluid retention [18].
There is no doubt that minoxidil can be effective for hair growth and certain cases of hypertension. However, its use in patients with cardiovascular disease should be approached with extreme caution [17]. The risk-to-benefit ratio has to be considered for each of the cases, as the use of minoxidil is not entirely safe for patients with cardiovascular disease.