Vitamin PP: Pharmacokinetics and Biochemistry
Drugs of this group are absorbed from the intestinal lumen into the systemic circulation unchanged. Upon reaching the liver, the molecules are actively incorporated into biochemical processes, acting as substrates for the synthesis of crucial coenzymes. These include NAD (nicotinamide adenine dinucleotide) and NADP (nicotinamide adenine dinucleotide phosphate), which facilitate key oxidation-reduction reactions in tissues.
Vitamin PP is widely distributed in nature. Plant sources include whole-grain bread, mushrooms, nuts, vegetables (tomatoes, peppers), and legumes (soybeans, peas, beans). Animal sources include meat, fish, and organ meats (heart, kidneys, liver).
Pharmacodynamics: Nicotinic Acid vs. Nicotinamide
The group comprises two main substances: nicotinamide and nicotinic acid (known by the trade name niacin). Both forms possess potent antipellagra activity, but their pharmacological profiles differ significantly.
Only nicotinic acid is capable of exerting the following specific effects:
- Vascular action: Causes marked vasodilation and increases vascular permeability.
- Effect on hemostasis: Stimulates blood fibrinolytic activity.
- Antiatherogenic action: When prescribed in high doses (3–4 g per day), it acts as a hypolipidemic agent. It inhibits the synthesis of very-low-density lipoproteins (VLDL), reduces the concentration of triglycerides and low-density lipoproteins (LDL), while simultaneously increasing the level of antiatherogenic high-density lipoproteins (HDL).
It is important to remember that nicotinamide completely lacks both vasodilating and hypolipidemic properties.
Clinical Applications of Vitamin PP Preparations
The main indication for prescribing both forms is the prevention of hypovitaminosis and the treatment of pellagra.
In gastroenterology and hepatology, these drugs are used for liver diseases (cirrhosis, hepatitis) and gastritis accompanied by reduced acidity. They also stimulate tissue regeneration in slow-healing ulcers and wounds.
Specific indications for nicotinic acid include the combination therapy of ischemic cerebrovascular disorders, atherosclerosis, and vascular spasms of the extremities. For long-term therapy, a sustained-release form of nicotinic acid—Enduracin tablets—has been developed.
Vitamin P (Bioflavonoids): Properties and Sources
The bioflavonoid group includes rutoside (rutin), dihydroquercetin (quercetin), hesperidin, and other compounds. Unlike vitamin PP, they are of exclusively plant origin. They are abundant in citrus fruits, black currants, rose hips, rowan berries, green tea, and nuts. Bioflavonoids are not found in animal products.
The primary pharmacological effect of vitamin P is angioprotective. These agents regulate vascular wall permeability, reduce capillary fragility, and exert a hypotensive effect. In addition, they exhibit antioxidant activity and choleretic properties.
Bioflavonoids interact closely with vitamin C. They convert ascorbic acid into monodehydroascorbic acid, which facilitates its penetration into cells. The action of combination drugs, such as Ascorutin (a combination of rutoside and ascorbic acid), is based on this mechanism.
Indications for Bioflavonoid Administration
Vitamin P preparations are used for the prevention and treatment of specific deficiency states (hypo- and avitaminosis P).
In angiology, they are indicated for vascular pathology: increased capillary permeability and venous insufficiency, including thrombophlebitis.
In traumatology, bioflavonoids effectively combat edema of various origins and are used in the treatment of mechanical injuries and frostbite.