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Metocinium Iodide

Methacinum

For medical students2 min readUpdated 2026-10-10

Metocinium iodide (Methacinum) is a pharmaceutical agent that regulates the function of the peripheral nervous system. The drug is used in medical practice in the form of tablets and injection solutions for various routes of administration.

Pharmacological GroupAgents regulating the peripheral nervous system

Dosage FormsTablets 0.001 g and 0.002 g; 0.1% solution in 1 mL ampoules

Oral Administration0.002–0.004 g 2–3 times daily

Maximum Oral DosesMax single dose (MSD) — 0.005 g, Max daily dose (MDD) — 0.015 g

Maximum Parenteral DoseMax daily dose (MDD) — 0.006 g (IV, IM, and SC)

Mechanism of Action

The drug affects the peripheral nervous system, purposefully regulating its functions and interaction with effector organs due to its chemical structure and pharmacodynamic properties.

Pharmacological Effects

The action of Methacinum is aimed at regulating autonomic functions of the body. The drug provides the necessary therapeutic response from peripheral nerve structures by blocking or stimulating impulse transmission depending on the clinical objective.

Indications for Use

The drug is prescribed as part of combination therapy for conditions requiring pharmacological regulation of peripheral nervous system functions, in accordance with guidelines and clinical protocols.

Side Effects and Safety

When using the drug, it is essential to strictly follow the dosing regimen. Exceeding the maximum single doses (MSD) and maximum daily doses (MDD) is unacceptable, as it may lead to adverse drug reactions. The physician should consider the route of administration: for oral administration, the maximum daily dose is 0.015 g, while for parenteral administration (IV, IM, SC) it is 0.006 g.

Administration and Dosage

Methacinum is available in two main dosage forms: tablets (0.001 g and 0.002 g) and injection solution (0.1%, 1 mL in ampoules). Orally, it is prescribed at 0.002–0.004 g 2–3 times a day. Parenterally (intravenously, intramuscularly, or subcutaneously), 0.5–2 mL of a 0.1% solution is administered. It is important to remember the maximum dose limits: maximum single oral dose is 0.005 g, maximum daily oral dose is 0.015 g, and maximum daily parenteral dose is 0.006 g.

Mnemonic

Metacin — one step to the periphery: tablet or ampoule under strict control of maximum doses (0.015 orally / 0.006 parenterally).

Frequently asked questions

What specific pharmacological group and subgroup does metocinium iodide belong to?

Metocinium iodide (referred to in sources as metacin) belongs to the pharmacological group of muscarinic acetylcholine receptor antagonists (anticholinergics). Within this classification, it is part of the synthetic drugs subgroup. Chemically, it is a quaternary ammonium compound with predominantly peripheral action. Metacin is used to relax smooth muscle, provide tocolysis, and suppress undesirable vagal reactions during premedication.

In what specific diseases and conditions is metocinium iodide indicated?

The drug is used to treat spastic conditions and suppress vagal reactions. Indications for metacin include:

Smooth muscle spasms — gastrointestinal spasms, as well as biliary and renal colic.
Bronchial asthma.
Tocolysis.
Premedication before anesthesia and suppression of vagal reactions.

Does metocinium iodide cross the blood-brain barrier and affect the CNS?

Metocinium iodide does not cross the blood-brain barrier and exerts exclusively peripheral effects. The drug is a quaternary ammonium compound. Unlike tertiary amines such as atropine and scopolamine, which can cross the blood-brain barrier and cause central effects, metacin has no central nervous system action.

How does metocinium iodide differ from atropine in chemical structure and pharmacodynamics?

The main differences lie in origin, chemical structure, and the ability to penetrate the central nervous system.

Characteristic	Atropine	Metacin
Origin	Natural product	Synthetic drug
Chemical Structure	Tertiary amine	Quaternary compound
Blood-Brain Barrier (BBB) Penetration	Crosses the BBB	Does not cross the BBB
Pharmacodynamics	Exerts central effects (excitation)	Peripheral action only

Both drugs are muscarinic antagonists and are used for premedication, but metacin is additionally used for tocolysis, whereas atropine serves as an antidote for muscarinic agonist poisoning.

What are the main dosage forms of Metocinium Iodide?

The drug is available as 0.001 g and 0.002 g tablets, as well as a 0.1% solution in 1 mL ampoules.

What is the maximum daily dose of the drug when taken orally?

The maximum daily dose (MDD) for oral administration is 0.015 g, and the maximum single dose (MSD) is 0.005 g.

How is Metocinium Iodide administered parenterally?

Parenterally, the drug is administered intravenously, intramuscularly, or subcutaneously at 0.5–2 mL of a 0.1% solution, with a maximum daily dose of 0.006 g.

Go deeper

Pharmacodynamics of agents affecting the peripheral nervous system
Rules for calculating maximum doses (MSD and MDD) in prescriptions
Comparison of oral and parenteral routes of drug administration
Toxicological profile and management of overdose
Pharmacokinetics of ampoule and tablet formulations