INTRODUCTION:

Rifapentine is a rifamycin class antibiotic structurally related to rifampin and rifabutin. It is primarily used in the treatment of tuberculosis, usually in combination therapy and often in once- or twice-weekly regimens due to its long half-life. The drug acts by inhibiting DNA-dependent RNA polymerase, thereby blocking transcription and preventing bacterial protein synthesis. It exhibits strong activity against Mycobacterium tuberculosis and Mycobacterium leprae and a synthetic derivative of natural products of the bacterium, Amycolatopsis mediterranei. These agents are considered bactericidal and are active against both intracellular and extracellular organisms.¹

World Health Organisation suggests the use of rifapentine as an alternate first-line treatment for TB. Rifapentine was first synthesized in 1965 by the same company that produced rifampin. The drug was approved by the Food and Drug Administration (FDA) in June 1998. It is synthesized in one step from rifampicine. Rifapentine is approved for the treatment of tuberculosis in the US. The drug is also used in China. Rifapentine has a long half-life which allows for once-weekly administration. When administered twice weekly during the intensive phase and once weekly during the continuation phase, rifapentine has demonstrated efficacy in the treatment of pulmonary tuberculosis in immune-competent patients.²

Don’t be Surprised: rifapentine tablets are red in color, and people taking rifapentine may notice their urine, sweat, or tears turn red or orange. This effect is harmless and will disappear soon after finishing treatment.³

Generic name: Rifapentine

IUPAC Name: 3{[(4-cyclopentyl-1-piperazinyl)imino] methyl}rifamycin

Route of administration: Oral

Chemical Formula: C₄₇H₆₄N₄O₁₂

Molar mass - 877.031 g/mol

Melting Melting point: 179 to 180^oC

Solubility solvent: Methanol, 0.1NHCl, Acetonitril,

Sodium dihydrogen orthophosphate and 0.01M Potassium dihydrogen phosphate buffer pH (6.0)

Fig: Structure of Rifapentine

MECHANISM OF ACTION:

Rifapentine is a semisynthetic cyclopentyl rifamycin antibiotic, generally prescribedfor the treatment of tuberculosis (TB), with a serum half-life several times higherthan rifampicin, which can provide less frequent dosing in comparison with standardregimens.⁴ Similar to other rifamycins, the lipophilic nature of rifapentineallows it to readily diffuse across the bacterial cell membrane where it binds the B-subunit of RNA polymerase, thereby inhibiting the elongation of messenger RNA⁵. Importantly, this mechanism also operates against the metabolically dor-mant bacilli associated with latent TB infection (LTBI). Unfortunately, the shared mechanism of action between rifamycins also leads toextensive cross-resistance, that is, a rifampicin-resistant TB strain would similarly be resistant to rifapentine.⁶

Analytical Methods:

The main purpose of development of analytical methods are for identification, purification and finally to quantification any required drug etc., The main activities involved in the analytical development of a method are separation and characterization of impurities as well as degraded products, analytical investigations, studies for identification and finally setting up of parameters optimization to specific requirements.⁷Analytical methods in rifapentine refer to the scientific techniques and procedures used to identify, quantify, and evaluate the quality, purity, strength, and concentration of rifapentine in its bulk drug, pharmaceutical formulations, and biological samples.

UV-Visible Spectroscopy Analytical Development Methods:

This method, characterized by its ease of use, simplicity, accuracy, validity, and cost-effectiveness, emerges as avaluable analytical tool, particularly in determining theconcentration of absorbing species when applied to pure compounds with appropriate standard curves. UV spectroscopy emerges as a powerful analytical tool, utilizing light within the UV or visible region with wavelengths ranging from 200 to 800 nm. This technique stands versatile, capable of analyzing both colorless compounds in the UV range (400-200 nm) and colored compounds in the visible range (800-400 nm). The application of Beer's law, a universal principle in UV spectroscopy, elucidates the absorption of radiant energy by samples.⁸

PARAMETER	Development and Validation of UV/VisibleSpectrophotometric Method for theEstimation of Rifapentine in Bulk andPharmaceuticalFormulations
Pharmaceutical Dosage Form	Bulk Drug dosage form
Instrument	Shimadzu UV-1800 / Chemito UV-2600 Double Beam UV-Visible Spectrophotometer
Solvent	Methanol
Detector	Silicon Photodiode Detector
Light Source	Deuterium and Halogen Lamps
Cell Type	Quartz cell (10 mm path length)
λmax	478 nm
References	1

PARAMETER	Development and validation of UV-visible spectrophotometric method for estimation of rifapentine in bulk and dosage form
Pharmaceutical Dosage Form	Tablet dosage form
Instrument	ChemitoUV 2600 spectrophotometer
Solvent	0.1N HCL
Detector	UV Probe software
Light Source	N/A
Cell Type	Quartz cells(1 cm matched)
λmax	478nm
REFERENCES	2

UV-Spectrophotometry analytical development Methods:

Rapid and easy analytical methods are needed due to increasing number of multicomponent formulations, biotherapeutic products and samples of complex matrix in que.Different types of UV spectrometric methods developed on the basis of principle of additivity, absorbance difference, processing absorption spectra.The basic principle behind the UV spectroscopy is absorption of visible and UV radiation (200–400 nm) is associated with excitation of electrons, in both atoms and molecules, from lower to higher energy levels.⁹The UV-Spectrophotometry Area Under the Curve (AUC) method for rifapentine is proposed as a simple, precise, accurate, sensitive, and economical technique for determining the drug in bulk and pharmaceutical formulations (tablets, bulk).

Parameter	Quantitative estimation of rifapentine using UV-spectrophotometry- Area under curve technique in bulk and tablets
Pharmaceutical Dosage Form	bulk and tablets
Solvent used	Methanol
method: Area under curve (AUC)	Scanned from 200-400 SSSSnm. In this method Area under Curve (AUC) was integrated in the wavelength range of 307 -350 nm.
Concentration Range	4 - 24 µg/mL
Reference	3

RP-HPLC Analytical development methods:

Reversed-phase chromatography is the mainly used in chromatographic mode, it is used to separate neutralmolecules in solution based on their hydrophobicity. As the name suggested that, reversed-phase chromatography (often referred to as RP chromatography) is the reverse of normal-phase chromatography in the intelligence that it involves the employ of a polar mobile phase and a non-polar stationary phase. It ensures that a decrease in the polarity of the mobile phase results in a decreasein solute retention. The components which have more affinity towards stationary phase willelutedlast while the components which haveless affinity to stationary phase eluted first¹⁰.

Parameter	Analytical Method Development and Validation of Impurity Profile in Rifapentine	Method Development, Validation, and Estimation of Rifapentine in Bulk and tablet dosage form by Using UV-Spectrophotometry and RP-HPLC method	(Marketed Formulation)
Pharmaceutical dosage form	Bulk dosage form	Bulk dosage form	Marketed Formulation (Rifapex 150 mg tablet)
Mobile Phase solvent (A)	0.025M sodium dihydrogen orthophosphate buffer (pH 7.7): Acetonitrile (90:10 v/v)	Acetonitrile: 0.01M buffer pH (6.0)	Acetonitrile: 0.01M buffer pH (6.0)
Mobile Phase solvent (B)	0.025M sodium dihydrogen orthophosphate buffer (pH 7.7): Acetonitrile (30:70 v/v)
Ratio (v/v)	30:70	80:20	80:20
Stationary Phase	Thermo BDS-Hypersil C18 (250mm × 4.6mm, 5µm)	C18 (4.6ID x 250mm) in isocratic mode	C18 (4.6ID x 250mm) in isocratic mode
Flow Rate	1.0 mL/min	0.8 ml/min	0.8 ml/min
Wavelength (λ)	254 nm (Wavelength of maximum absorption (λ)	478 nm (Wavelength of maximum absorption (λ)	478 nm (Wavelength of maximum absorption (λ)
Retention Time	1.00	5.00 ± 0.1 minute	5.00 ± 0.1 minute
Reference	12	11	11

Parameter	RP-HPLCMethod Development and Validation for Simultaneous Estimation of Isoniazid andRifapentine in SyntheticMixture	Development And Validation Of Rp-Hplc Method for Determination Of Rifapentine andMoxifloxacin HydrochlorideIn Bulk and TabletDosage Form
Pharmaceutical dosage form	Tablets dosage form	Bulk dosage form
Instruments	Shimadzu LC-2010 CHT	LC-20 Shimadzu
Detector	UV Detector Software, LC Solution version 1.25 for separation	PDA
Mobile Phase solvent	Acetonitrile: Phosphate buffer pH 4 (85:15 %v/v) with pH adjusted to 6 with 1% Triethylamine (TEA)	Methanol: Sodium phosphate dihydrate buffer, 70:30 (v/v)
Stationary Phase	Shim-pack solar C18 (250mm × 4.6 mm, 5µm)	Qualisil BDS C18 (250 mm x 4.6 mm
Flow Rate	1.0 ml/min	1.0 ml/min
Wavelength (λ)	262 nm (considered satisfactory for both drugs).	270
Retention Time	4.283 min	7.35 0.2 minutes
Reference	13	14

HPTLC Analytical Development Methods:

HPTLC is a most versatile technique and is known for uniformity, purity profile, assay values and precision and accuracy of results. It can handle several samples of even divergent nature and composition. HPTLC is a modern analytical separation method with extensive versatility, although already much utilized, is still with great potential for future development in research and development. It is accepted as a time-saving and most economical machine practically with minimum trouble shootings. HPTLC method is having active application in qualitativeand quantitative analysis of a wide range of compounds, such asherbal and botanical dietary supplements, nutraceuticals, traditionalwestern medicines, traditional Chinese medicines and Ayurvedic (Indian) medicines.¹⁵

Parameter	Result/value
Pharmaceutical dosage form	Tablet dosages form
Stationary Phase	Silica gel 60GF254
Mobile phase	methanol: toluene: aceticacid (3:7:0.1, v/v/v)S
Wavelength (λ)	478 nm
Retardation Factor	0.5 ± 0.02
Reference	16

LC-MS/MS Analytical Development Methods:

LC-MS/MS (Liquid Chromatography-Tandem Mass Spectrometry) is an advanced analytical technique that combines liquid chromatography for separating compounds with two stages of mass spectrometry for highly sensitive and selective identification and quantification.

PARAMETERS	Validation and application of a quantitative liquid chromatography tandem mass spectrometry assay for the analysis of rifapentine and 25-O-desacetyl rifapentine in human milk	Determination of the Rifamycin Antibiotics Rifabutin, Rifampin, Rifapentine and their Major Metabolites in Human Plasma via Simultaneous Extraction Coupled with LC/MS/MS	Quantification of Rifapentine, a Potent Antituberculosis Drug, from Dried Blood Spot Samples Using Liquid chromatographic Tandem Mass Spectrometric Analysis
Mobile phase	acetonitrile: methanol: 0.1% formic acid (55/5/40, v/v/v)	Acetonitrile: methanol: formic acid and trifluoroacetic acid 0.1%(0.5:55:45, v/v/v)	aqueous mobile phase (A): ammonium formate in water organic mobile phase (B):3% DMSO in acetonitrile
Flow Rate	450 µL/min	2.45 minutes	4.0 minutes
Column	Agilent® Poroshell 120 EC-C18 column (4.6 mm × 50 mm, 2.7 µm particle size)	C18 column (10 cm × 4.6 mm, 5 μm particle size)	Waters BEH C8 column (particle size)
Instrumentation	AB Sciex API 4000 triple quadrupole mass spectrometer	API 5000 triple quadrupole mass spectrometer	AB Sciex QTRAP 5500 mass analyzer
Concentrations ranged	2.00–2000 ng/mL	60.061ng/ml to 8008.134 ng/ml	50ng/ml-150ng/ml
Reference	17	18	19

CONCLUSION:

Method that was developed forthe determination ofRifapentine based on different analyticaltechniques, UV-Spectrophotometric, RP-HPLC, HPTLC LC-MS/MS method. The method was validated and found to be simple, sensitive, accurate, and precise. Hence, the method can be used successfullyforroutine analysis of pharmaceutical dosage form of Rifapentine. However, it can serve as an alternative where advanced instruments (e.g.HPLC) are not available forroutine analysis.

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Received on 09.10.2025 Revised on 23.11.2025

Accepted on 27.12.2025 Published on 22.01.2026

Available online from January 29, 2026

Asian J. Pharm. Res. 2026; 16(1):101-105.

DOI: 10.52711/2231-5691.2026.00014

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Creative Commons License.