1-Bromo-3,5-dimethyladamantane pharma grade API, manufacturer material code ADM-Br-DM-GMP-01, is a halogenated adamantane derivative supplied for the preparation of tablets, capsules, granules, oral liquid intermediates, and injectable presentations. The compound is assigned CAS 941-37-7, has the molecular formula C₁₂H₁₉Br, and has a molar mass of 243.18 g/mol. No dedicated USP or Ph. Eur. monograph for this exact derivative is published; the pharma grade is therefore released against an ICH Q6A-compliant internal specification filed in the active substance master file. The material is produced in closed stainless-steel and glass-lined equipment under nitrogen inertisation in batch sizes of 5 kg to 25 kg. Two physical grades are supplied: a direct-compression grade with controlled particle size for oral solid dosage manufacturing, and a low-endotoxin sterile dry powder grade for injectable compounding and lyophilization.

The product differs from technical-grade 1-bromo-3,5-dimethyladamantane by control of related brominated adamantane congeners, residual solvents, elemental impurities, particulate matter, and bacterial endotoxins. The technical grade may have an assay of 90–95% by gas chromatography and may contain 2–10% of 1,3-dibromo-5,7-dimethyladamantane; the pharma grade assay is specified at 98.5–101.5% on the anhydrous, solvent-free basis, with dibromo congener limited to ≤ 0.20%.

Which Solid-State Properties Govern Tablet, Capsule, and Granule Performance?

The product is a low-melting crystalline or waxy crystalline solid with a specified melting interval of 52 °C to 58 °C. This narrow melting interval is used as an identity and purity indicator because the presence of amorphous content, co-crystallized solvent, or non-volatile brominated homologues can depress the melting onset and broaden the endotherm. The particle size distribution is controlled by laser diffraction according to USP <429> and Ph. Eur. 2.9.31. The direct-compression grade is released with D50 20–50 µm and D90 ≤ 150 µm to support die filling, content uniformity, and dissolution in low-dose tablet and capsule formulations. A granulated-grade variant with D50 50–100 µm is used for high-shear wet granulation runs where excessive fines increase binder demand and impeller torque variability.

Bulk density and tapped density are controlled at 0.45–0.65 g/mL and 0.55–0.75 g/mL, respectively; the Carr compressibility index is maintained below 20 to reduce segregation during transfer from bin blenders to rotary press feed frames. Because the melting interval is below typical fluid-bed inlet air temperatures, wet granulation with inlet air above 45 °C is restricted unless the binder solution is cooled and the product bowl is jacketed. Dry granulation by roller compaction with screen milling through a 1.0 mm rasp is preferred. The total fines fraction below 150 µm should be kept below 30% for tablets and below 25% for hard gelatin capsule filling to avoid weight variation caused by powder fluidisation and static adhesion.

Encapsulation of the direct-compression grade on a dosator-type capsule filler requires monitoring of pin temperature. At pin temperatures above 30 °C, surface softening of the low-melting particles can produce pin adhesion, leading to intermittent capsule weight failures. Rotary compression of the direct-compression grade is typically conducted with die table cooling to keep the contact surface below 35 °C. Published solid-state screening data for this specific brominated dimethyladamantane are limited; lot-specific XRPD analysis is therefore included in release and should show no low-angle amorphous halo above 5% relative intensity by peak integration.

Residual Solvent and Elemental Impurity Limits Under ICH Q3C and ICH Q3D

Because the bromination and dimethylation sequence uses halogenated and non-halogenated reaction solvents, the pharma grade is released with a gas chromatographic residual solvent profile according to USP <467> and Ph. Eur. 2.4.24. Class 2 solvents are controlled as follows: dichloromethane ≤ 600 ppm, methanol ≤ 3000 ppm, toluene ≤ 890 ppm, and n-hexane ≤ 290 ppm. Class 1 solvents are controlled at a limit of ≤ 2 ppm for benzene and ≤ 5 ppm for 1,2-dichloroethane. Residual water is controlled to ≤ 0.5% by Karl Fischer titration because the brominated cage is hydrolytically sensitive under alkaline aqueous conditions.

Elemental impurity control follows ICH Q3D and USP <232>/<233>. The injectable grade is released with limits of ≤ 10 ppm for palladium, ≤ 5 ppm for nickel, ≤ 3 ppm for chromium, and ≤ 1 µg/g each for cadmium, lead, and arsenic. The oral grade applies the corresponding ICH Q3D oral concentration conversions documented in the route-specific risk assessment. Analysis is performed by inductively coupled plasma mass spectrometry after closed-vessel microwave digestion.

For injectable formulation, the selected pharma grade should be the sterile dry powder or lyophilized presentation rather than the oral tablet grade. The compound is practically insoluble in water; direct aqueous reconstitution does not yield a solution suitable for parenteral administration. Solubilised systems based on ethanol and propylene glycol or a parenteral cyclodextrin are required. Terminal sterilization of aqueous solutions should not be assumed because the brominated adamantane can undergo hydrolytic debromination at pH above 8.0 and during prolonged exposure above 121 °C. Sterile filtration through a 0.22 µm PVDF or PTFE membrane is preferred for formulations that permit filtration. Lyophilized vials should be annealed below the collapsed product glass transition temperature to avoid melt-back; published data for this specific configuration are limited.

When the Substance Is Prepared as an Oral or Injectable Intermediate

Oral granules of the direct-compression grade are typically filled into hard gelatin capsules at fill weights between 50 mg and 400 mg. The excipient selection should avoid lactose-based matrices under accelerated stability conditions of 40 °C/75% RH if the low-melting API can co-plasticize the capsule shell; a microcrystalline cellulose and dibasic calcium phosphate anhydrous matrix is used to reduce this risk. The compound should not be combined with strongly alkaline excipients such as magnesium oxide or sodium carbonate in a wet granulation process because pH above 8.0 accelerates debromination and produces 3,5-dimethyladamantane-related impurity. For direct compression, external lubrication with sodium stearyl fumarate at 0.5–1.5% w/w is used instead of magnesium stearate if magnesium is restricted or if prolonged mixing causes punch filming.

For injectable presentations, a lyophilized 20 mL vial may contain 10–50 mg of the active substance per vial, with mannitol or glycine as bulking agent. Reconstitution with Water for Injection produces a slightly opalescent solution only when a co-solvent or cyclodextrin is included; direct aqueous reconstitution fails because of the water solubility limitation. The terminal sterilization boundary is 121 °C for 15 min only after pH adjustment to 4.5–5.5 and protection from light. Outside this window, hydrolytic debromination can generate hydroxy dimethyladamantane impurity exceeding 0.5% within 24 h under accelerated aqueous stress conditions.

Comparative Impurity and Stability Boundaries Against Technical Grade Material

Compared with 1-bromoadamantane, the 3,5-dimethyl substitution raises steric bulk around the brominated bridgehead carbon and lowers the melting interval from the 118–120 °C range typical of 1-bromoadamantane to the specified 52–58 °C interval. This changes storage and handling boundaries: the dimethyl derivative should be stored in sealed containers at 2–8 °C to avoid surface sintering, while 1-bromoadamantane can be stored at controlled room temperature. The dimethyl groups also reduce the rate of nucleophilic substitution at the bridgehead compared with 1-bromoadamantane, which is relevant in impurity control where residual starting material is labile to hydrolysis during capsule dissolution testing.

Compared with 1,3-dibromo-5,7-dimethyladamantane, the monobromo pharma grade carries a lower covalent bromine mass fraction, approximately 32.9% versus 49.3%, and provides a cleaner substitution pattern. The pharma grade restricts the dibromo congener to ≤ 0.20%; technical-grade material can carry 2–10% of this impurity. Because the dibromo congener is more hydrophobic and more difficult to remove by conventional crystallisation, control at the pharma grade level requires preparative purification and chromatographic or repeated recrystallisation steps.

The low-melting characteristic of the dimethyl derivative imposes specific boundaries in continuous manufacturing. Batch-to-batch variability on a twin-screw extruder with an L/D ratio of 40:1 has been observed when the API is fed as a fine powder without external lubrication; feed throat temperatures above 35 °C cause sticking at the screw root. Use of a side-stuffer at 150–250 rpm reduces segregation and stabilizes mass flow. For modified-release matrices, dissolution profiling under USP <711> apparatus II at 50 rpm in 0.1 M hydrochloric acid with 0.25% sodium dodecyl sulfate is used to discriminate lot-to-lot differences.