As a quaternary quinolinium iodide, 5-amino-1-methylquinolin-1-ium iodide is supplied as a non-sterile pharmaceutical-grade active pharmaceutical ingredient for further processing into tablet, capsule, granule, oral solution, and injectable dosage forms. The molecular formula is C₁₀H₁₁IN₂, and the formula weight is 286.12 g/mol. The compound consists of a 1-methylated 5-aminoquinolinium cation with a permanent positive charge and an iodide counterion. The supplier-specific model designation is not a compendial identifier; it may carry a grade code for oral solid processing or a reduced-bioburden grade for injectable manufacture. The material itself is not supplied sterile, and injectable use requires subsequent aseptic processing or terminal sterilization. The API is manufactured under ICH Q7 and the applicable parts of 21 CFR 210/211.

The finished-dose manufacturer retains responsibility for receiving and testing under 21 CFR 211.84 and ICH Q7 Section 11. The supplier’s batch release documentation includes the batch number, retest date, storage conditions, and approved specification. A drug master file or a certificate of suitability may be available for regulatory submissions.

What Release Specifications and Pharmacopoeial General Methods Apply to This Non-Monographed Quaternary Salt?

Because no dedicated monograph for this exact iodide salt appears in the United States Pharmacopeia, European Pharmacopoeia, or Japanese Pharmacopoeia, the release file is built from harmonized general chapters and ICH guidance. Identity is confirmed by infrared absorption spectrophotometry (Ph. Eur. 2.2.24, USP <197>) and by retention-time agreement in a validated HPLC-UV method. The iodide counterion is confirmed by silver nitrate precipitation (Ph. Eur. 2.3.1). Assay is determined by HPLC-UV against a qualified reference standard and is expressed on the dried basis. Related substances are controlled by area normalization with thresholds selected under ICH Q3A(R2); for a maximum daily dose of 2 g/day or less, the reporting threshold is 0.05%, the identification threshold is 0.10%, and the qualification threshold is 0.15%. Residual solvents are measured by headspace gas chromatography (Ph. Eur. 2.4.24, USP <467>) and are limited according to ICH Q3C; if methanol and dichloromethane are present in the synthesis, the acceptance limits are 3000 ppm and 600 ppm, respectively, while benzene is controlled at no more than 2 ppm as a Class 1 solvent. Elemental impurities are tested by inductively coupled plasma mass spectrometry or optical emission spectroscopy and limited under ICH Q3D according to the intended route and daily dose. Water content is determined by Karl Fischer titration (Ph. Eur. 2.5.12, USP <921>) because free water can alter powder flow and promote iodide mobility. Residue on ignition is determined by Ph. Eur. 2.4.14, and particle-size distribution is measured by laser diffraction (USP <429>, Ph. Eur. 2.9.31) when content uniformity or dissolution is sensitive to particle size.

For non-sterile oral-grade material, microbial enumeration and absence of specified microorganisms are controlled by Ph. Eur. 5.1.4, USP <61>, and USP <62>. For injectable-grade material, bioburden and bacterial endotoxins are controlled instead of the non-sterile microbial limits.

The solid-state form is characterized by X-ray powder diffraction if polymorphism affects dissolution or stability. Differential scanning calorimetry and thermogravimetric analysis are used to detect desolvation and degradation onset; quaternary ammonium iodides often decompose before melting, so melting-range identification may be less useful than spectroscopic and chromatographic identity tests. Moisture-sorption isotherm data may be used to set handling limits for low-humidity or dry processing. These solid-state parameters are supplier-specific and are validated under ICH Q2(R1); no harmonized compendial acceptance criteria exist for this exact salt. Published stability and filter-binding data for this specific quaternary iodide are limited, so the values applied in development are platform limits and must be confirmed on the supplier’s batch after forced-degradation studies.

For tablet and capsule manufacture, the API is first delumped through a 600 µm or 850 µm stainless-steel sieve. Direct compression is appropriate only when the powder has a Carr Index below 25% and a flow function coefficient above 4; otherwise roller compaction or wet granulation is selected. The blend is prepared in a diffusion blender at 50–70% of nominal vessel volume, with speed and time determined by blend uniformity mapping. Content uniformity is evaluated according to USP <905> or Ph. Eur. 2.9.40; an acceptance criterion of RSD ≤ 5.0% is commonly used for the active fraction. Low-dose strengths require geometric dilution of the API with a carrier excipient before final blending. The iodide counterion is incompatible with strong oxidizing agents and can oxidize to molecular iodine under light, trace-metal catalysis, or residual peroxides in povidone or crospovidone. Therefore, low-peroxide excipient grades, light-protected storage, and nitrogen blanketing of the blend are used where needed. Magnesium stearate lubrication is kept to the minimum time and shear required for tablet ejection because over-lubrication can reduce tablet tensile strength and slow dissolution of a highly water-soluble API. Tablet cores are compressed on a rotary tablet press with tooling matched to the granule particle-size distribution. Friability is controlled by USP <1216>, with a common acceptance limit of not more than 1.0% weight loss.

Dissolution testing for tablets and capsules uses USP <711> apparatus 1 or 2. A medium of 900 mL of 0.1 M HCl or phosphate buffer at pH 6.8 with 50 rpm basket or 75 rpm paddle rotation is a common starting point; the final method is selected by its ability to detect deliberate changes in disintegrant concentration, granule hardness, or lubricant level. For capsule filling, dosator or tamping-type machines may be used, and the fill weight is calculated from the active cation content. Because the active cation fraction of the iodide salt is 55.64%, a label claim expressed as the cation requires 1.797 times the corresponding salt weight. If the label claim is expressed as the neutral 5-aminoquinoline base equivalent, the salt weight factor is 1.985.

When the Same API Is Converted to Granules or an Injectable Solution

In wet granulation, the water-soluble quaternary salt can partially dissolve in the binder liquid and redistribute during drying, creating a risk of non-uniform drug content or localized degradation. Granulation is therefore performed with controlled liquid addition, impeller torque monitoring in a high-shear granulator, or pressure-differential monitoring in a fluid-bed granulator. The endpoint is defined by a torque or pressure-differential plateau rather than by a fixed time. High-shear granulation with a chopper speed above 1500 rpm may generate heat and promote iodide oxidation; therefore, jacketed bowls and cooled binder solutions are used when necessary. Roller compaction is an alternative for moisture-sensitive formulations, but it may reduce tablet tensile strength; ribbon density is controlled by roll pressure, roll speed, and gap width. These parameters are validated for the specific formulation rather than set from the API alone.

Drying is conducted at a controlled inlet-air dew point, typically below 10 °C, and at a product temperature below the degradation onset established by differential scanning calorimetry or thermogravimetric analysis. If the onset is low, vacuum drying or lyophilization is used; if stability is acceptable above 60 °C, conventional fluid-bed drying may be appropriate. These limits are product-specific and must be verified for the supplier’s lot.

For the injectable route, the API is dissolved in Water for Injection in a stainless-steel or glass-lined vessel. The iodide ion is redox-reactive; dissolved oxygen is reduced by nitrogen sparging, and the solution is protected from light throughout processing. The pH and buffer species are selected from forced-degradation data; the final solution is adjusted to an osmolality of 250–350 mOsm/kg measured by USP <785>. Terminal sterilization may be evaluated at 121 °C for an overkill F0 of 12 min, with cycle validation under USP <1229>; however, if the API is heat-labile, aseptic filtration through 0.45 µm followed by 0.22 µm polyvinylidene difluoride or polyethersulfone filters is used. Filtration is supported by filter-binding and compatibility studies; published data for this specific quaternary iodide are limited, so a worst-case mass-balance study is necessary. Aseptic filling is performed under ISO 5 conditions in an ISO 7 background. Type I borosilicate glass vials and halogenated butyl rubber stoppers with low extractable profiles are preferred; the container-closure system must not release metal ions or oxidizing agents. Finished injectable solution is tested for sterility by USP <71>, bacterial endotoxins by USP <85>, particulate matter by USP <788>, and container-closure integrity by USP <1207>. Extractables and leachables are evaluated under USP <1663> and USP <1664>. For an injectable-grade API, the endotoxin limit is calculated from the dose; the usual threshold is K/M, where K is 5 EU/kg body weight and M is the maximum dose per kg administered per hour.

For oral solution or granules for oral suspension, the same oxidation controls apply, but the process is less restrictive than injectable manufacture; the solution may be preserved if intended as a multidose form, and the dose is based on the active cation content rather than the salt weight.

Comparative Salt-Form Properties Relevant to Formulation

The table below compares the iodide salt with the neutral base, the chloride salt, and the bromide salt. The values are derived from the molecular formulas and are used for dose conversion and counterion risk assessment.

Compared with neutral 5-aminoquinoline, the 1-methylquinolin-1-ium iodide does not require pH adjustment to dissolve in water, which simplifies oral liquid and injectable preparation but removes pH-dependent solubility as a formulation control tool. The permanent cation may also alter permeability and tissue distribution; permeability should be measured directly for this salt rather than extrapolated from the neutral base. The iodide salt has a higher formula weight and a lower active cation fraction than the chloride or bromide salt; this affects fill weight, label claim, and content uniformity calculations. Because iodide is more polarizable and redox-active than chloride, the iodide salt requires more stringent protection against light, oxygen, trace metals, and oxidizing excipients. In contrast, the chloride salt is less redox-sensitive and provides a higher active moiety fraction, but it may introduce hydrochloride-related hygroscopicity and compatibility concerns. The bromide salt is intermediate with respect to formula weight and redox activity. Selection among these forms is determined by the intended route, total daily iodide exposure, container-closure compatibility, and the oxidative degradation threshold of the finished formulation.