Pharmacodynamics and pharmacokinetics
Dipiroximum (the main active ingredient is trimedoxime bromide) is a classic cholinesterase reactivator.
In its chemical structure, the drug belongs to quaternary ammonium compounds. This structural feature is critical for understanding its pharmacokinetics: the drug has low lipophilicity and poorly penetrates the blood-brain barrier (BBB). As a result, its action is limited to the peripheral nervous system — it effectively eliminates the peripheral effects of intoxication, but has virtually no effect on the central nervous system (CNS).
For comparison, tertiary amine drugs (e.g., isonitrosine) readily penetrate the CNS and relieve both peripheral and central symptoms.
Indications and clinical use
The drug belongs to emergency care agents and is used exclusively in an inpatient setting. Its main task is the reactivation of the enzyme in severe poisonings. It is administered parenterally (intramuscularly).
Contraindications
An absolute contraindication to its administration is poisoning with reversible anticholinesterase agents (specifically carbamates). In this type of intoxication, Dipiroximum is clinically ineffective and is not used.
Formulations and prescription guidelines
According to the prescription guide, the drug is available in two forms:
- Powder;
- 15% solution in 1 ml ampoules.
Administration regimen: Administered intramuscularly at a dose of 1 ml of a 15% solution. If symptoms persist and continued therapy is required, injections are repeated after 1–2 hours. The maximum total volume of the administered drug is strictly limited to 4 ml.
Prescription example for solution: Rp.: Sol. Dipiroximi 15% - 1 ml D.t.d. N. 10 in ampull. S. Intramuscularly, 1 ml. Repeat injection after 1-2 hours if necessary (maximum total dose — 4 ml).
Briefly: answers to topical questions
Poisoning with what specific substances indicates the use of dipiroxime?
The use of dipiroxime is indicated for acute organophosphate (OP) poisonings. Such toxic substances include insecticides, for example, malathion and trichlorfon.
The drug is a cholinesterase reactivator and predominantly eliminates peripheral effects of intoxication, as it poorly penetrates the blood-brain barrier. At the same time, dipiroxime is strictly contraindicated in poisonings with reversible anticholinesterase agents (carbamate group), as it is ineffective in these cases.
Through what chemical reaction does dipiroxime restore cholinesterase activity?
Dipiroxime restores cholinesterase activity via the chemical reaction of enzyme dephosphorylation.
The mechanism of the reaction includes the following stages:
- The reactivator, containing an oxime group, interacts with the phosphoryl residue of the organophosphate compound (OP) bound to acetylcholinesterase.
- The OP residue is cleaved from the enzyme.
- Enzyme activity is restored.
This reaction is effective in the first hours after poisoning, as later «complex aging» occurs and the chemical bond becomes stronger.
Quaternary ammonium compounds (Dipiroxime, Alloxime) have «four walls» that keep them out of the brain — they poorly cross the BBB and work only in the periphery.
Class and exam questions
Why does Dipiroxime not eliminate central poisoning effects?
Because in its chemical structure it is a quaternary ammonium compound and poorly penetrates the blood-brain barrier (BBB).
Can the drug be used for carbamate poisoning?
No, this is a strict contraindication. In poisoning with reversible anticholinesterase agents, reactivators are ineffective.
What is the maximum dose of the drug for intramuscular administration?
The total volume of the administered 15% solution must not exceed 4 ml. Typically, 1 ml is administered, repeating injections after 1-2 hours if necessary.
What is the main difference between Dipiroxime and Isonitrosine?
Dipiroximum (a quaternary compound) acts predominantly in the periphery, whereas isonitrosine (a tertiary amine) readily penetrates the CNS and eliminates both peripheral and central effects.
What else to study on this topic
- Pharmacokinetics of quaternary ammonium compounds and tertiary amines: the effect of structure on barrier penetration.
- Blood-brain barrier (BBB): anatomical and physiological features and permeability to drugs.
- Mechanism of action of reversible anticholinesterase agents (carbamates).
- Principles of emergency care for poisonings in an inpatient setting.
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