Pharmacokinetics and routes of administration
The pharmacological properties of the drug directly depend on its route of administration into the body:
- Sublingually (under the tongue): provides a rapid onset of effect within 2–5 minutes. It has a relatively high bioavailability (about 60%), and the duration of action is 1–2 hours (or 15 minutes to 2 hours when chewing the tablets).
- Orally (by mouth): acts more slowly (onset in 15–40 minutes). Due to significant first-pass hepatic metabolism, bioavailability drops to 20%. Regular tablets work for 4–6 hours, while prolonged-release (retard) forms provide an effect for 8–12 hours.
During oral administration, an important active metabolite is formed — isosorbide-5-mononitrate, which has a half-life of 2–4 hours.
Clinical application
In medical practice, the drug is prescribed in the following cases:
- Angina pectoris: sublingual forms are used for emergency relief of attacks, while oral forms are used for routine prophylaxis.
- Chronic heart failure: used as an effective vasodilator. It serves as an alternative therapy if ACE inhibitors cannot be prescribed for any reason.
Side effects and dosage forms
In terms of its adverse reaction profile, the drug is similar to nitroglycerin, but is somewhat better tolerated by patients — side effects are less pronounced.
In addition to standard tablets for sublingual and oral administration, additional dosage forms are available:
- Solutions intended for intravenous administration;
- Special transdermal systems (e.g., Nisopercuten) for cutaneous use.
Briefly: answers to topical questions
What are the absolute contraindications for isosorbide dinitrate?
Contraindications and limitations for isosorbide dinitrate include:
- hypertrophic cardiomyopathy with left ventricular outflow tract obstruction;
- severe aortic stenosis — use is not recommended or requires extreme caution;
- concomitant use of phosphodiesterase type 5 inhibitors, including sildenafil and its analogs;
- concomitant use of riociguat is contraindicated.
Which drugs are incompatible with isosorbide dinitrate?
Isosorbide dinitrate must not be combined with phosphodiesterase type 5 inhibitors, including sildenafil and its analogs, due to the risk of severe hypotension. Co-administration with riociguat is contraindicated. Combining it with alpha-blockers may lead to severe hypotension. Calcium channel blockers are also listed as interacting with nitrates.
What is the exact molecular mechanism of action of organic nitrates on vascular smooth muscle?
The mechanism of action of organic nitrates is associated with the enzymatic release of nitric oxide (NO) involving thiol enzymes and tissue sulfhydryl groups (SH groups). In target cells, NO interacts with Fe²⁺ ions part of guanylyl cyclase, activating this enzyme. This leads to the formation of cyclic GMP (cGMP), which alters enzyme activity. Organic nitrates cause vasodilation, affecting both capacitance and resistance vessels.
Class and exam questions
What is the difference between sublingual and oral routes of administration?
With sublingual administration, the onset is faster (in 2–5 minutes) with a bioavailability of 60%. Oral administration yields an effect in 15–40 minutes, and bioavailability drops to 20% due to first-pass hepatic metabolism.
What is the main active metabolite formed upon drug administration?
During oral metabolism, the active substance isosorbide-5-mononitrate is formed, with a half-life of 2–4 hours.
What are the indications for prescribing isosorbide dinitrate in heart failure?
The drug is used as a vasodilator as an alternative agent if the patient has contraindications to ACE inhibitors.
What else to study on this topic
- Comparison of the mechanism of action of nitrates with nitroglycerin
- Pharmacokinetic features of the active metabolite isosorbide-5-mononitrate
- Use of prolonged-release (retard) forms in the prevention of angina
- Mechanisms of development of tolerance to nitrate drugs
- Use of transdermal therapeutic systems in cardiology
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