Dihydropyridine vs Nondihydropyridine

If you have high blood pressure, then you’re most likely familiar with calcium channel blockers. These are drugs that your doctor prescribes in order to lower your blood pressure. Calcium channel blockers target the arterial smooth muscles, forcing them to relax and bring about peripheral vasodilation, a process that leads to a lower blood pressure. While all calcium blockers rely on this process to cure high blood pressure, they are still differentiated into two categories: dihydropyridine and nondihydropyridine. If your drug falls into the dihydropyridine category, then you’re most likely using Felodipine, Nifedipine, Nicardipine, or Amlodipine for your blood pressure treatment. On the other hand, if your doctor prescribed you a nondihydropyridine drug, then you get to choose between Verapamil or Diltiazem, the two most popular nondihydropyridine drugs in the market. You may be wondering, why do calcium blockers come in two types if they utilize the same process in targeting the arterial smooth muscles? The reason for this is because DHP and non-DHP drugs have significant differences ranging from toxicity levels, hemodynamic side effects, and drug interactions.

First off, with regards to inotropic effects, DHP drugs score higher in peripheral vasodilation as compared to non-DHP drugs. This means that DHP drugs don’t reduce calcium concentrations as much as non-DHP drugs do. Instead, they rely on an increase in sympathetic tone via baroreceptors, which leads to a positive inotropic effect. Non-DHP drugs, on the other hand, have a negative inotropic effect because they minimize calcium concentrations and negatively affect cardiac function. This means that patients with cardiovascular disorders should not take non-DHP drugs. Doctors usually prescribe DHP drugs to avoid aggravation of cardiovascular disorders.

Secondly, non-DHP drugs don’t negatively affect the heart rate of patients. In fact, it’s helpful in treating heart rate irregularities such as arrhythmia. Non-DHP drugs focus on slow atrioventricular conduction as well as lowering the rate of the sinoatrial node. This process is perfect for the treatment of atrial fibrillation as well as supraventricular tachyarrhythmias, or “arrhythmia” in layman’s terms. On the other hand, DHP drugs don’t affect the sinoatrial node nor the atrioventricular conduction, rendering them ineffective for treatment of arrhythmia. There are even reports that DHP drugs increase the heart rate rather than normalizing it.

Thirdly, both DHP and non-DHP drugs have their share of negative side effects. As mentioned earlier, patients with cardiovascular disorders cannot take non-DHP drugs, while DHP drugs tend to increase the heart rate. Additionally, DHP drugs are not prescribed for pregnant patients because they cause dizziness, headache, and flushing. Both DHP and non-DHP drugs may also trigger constipation and acid reflux.

In terms of drug interactions, non-DHPs tend to block the effect of cytochrome enzymes as well as the P-glycoprotein drug transporter. This means that all drugs that are taken in by the enzyme system have increased effects on the whole body. It should also be noted that because non-DHP drugs normalize the heart rate, they should not be taken simultaneously with beta-blockers because this may result in the blockage of the AV node.

Summary:

DHP and non-DHP drugs are used to treat high blood pressure. While they utilize the same basic process of vasodilation, they have additional mechanisms which may make them appropriate for certain conditions.

The positive, inotropic effects of DHP drugs make them ideal for patients with cardiovascular conditions. On the other hand, the calcium-reducing effects of non-DHP drugs trigger a negative inotropic response which may aggravate cardiovascular disorders.

Non-DHP drugs normalize the heart rate and are especially helpful for patients with arrhythmia. DHP drugs do the opposite and should not be taken by patients seeking to normalize the heart rate because it has been shown to increase the heart rate rather than reduce it.

DHP drugs should not be taken by pregnant patients because they bring about dizziness, headache, and flushing. All calcium channel blockers may trigger constipation and acid reflux.

Non-DHP drugs enhance the effects of all drugs taken in by the enzyme system. Furthermore, non-DHP drugs should not be taken in cohesion with beta blockers.

Sharing is caring!