In the pharmaceutical industry, the combination of Rifampicin (150 mg) and Isoniazid (75 mg) is a cornerstone Fixed-Dose Combination (FDC).

As a pharmacist and manufacturer, I classify this as the “Maintenance Phase” (or Continuation Phase) workhorse. After the initial intensive attack on Tuberculosis (TB), this $2\text{-}in\text{-}1$ ratio is used to ensure the complete eradication of remaining bacteria while significantly reducing “pill burden”—the primary factor in preventing the development of Multi-Drug Resistant TB (MDR-TB).

Primary Clinical Uses

• Pulmonary Tuberculosis: Used during the continuation phase of treatment (typically months 3 through 6) to eliminate “persister” bacilli.

• Extra-pulmonary Tuberculosis: Treatment of TB located in the bones, lymph nodes, or central nervous system.

• Latent TB Infection (LTBI): Often used in high-risk patients (such as those with HIV or household contacts of active TB cases) as preventive therapy to stop the infection from becoming active.

Dual Mechanism of Action: The Synergistic Attack

These two APIs attack Mycobacterium tuberculosis through entirely different pathways, ensuring that the bacteria cannot easily develop resistance.

Isoniazid (INH): The Cell Wall Destroyer

Action: It inhibits the synthesis of mycolic acids, which are unique and essential components of the mycobacterial cell wall.

Result: Without this waxy protective layer, the bacteria become fragile and die. It is highly effective against rapidly dividing bacilli.

Rifampicin: The Genetic Silencer

Action: It inhibits bacterial DNA-dependent RNA polymerase.

• • Result: This prevents the bacteria from transcribing DNA into RNA, effectively stopping them from making the proteins necessary for survival. It is a powerful “sterilizing agent” that kills slow-growing or semi-dormant bacteria.

The Manufacturer’s Perspective: Technical & Export

From a production and global trade standpoint at your WHO-GMP facility in Mumbai, this FDC is a high-volume essential:

• Rifampicin Stability: Rifampicin is notoriously sensitive to moisture and can act as a catalyst for the degradation of Isoniazid if the formulation isn’t optimized. At our facility, we prioritize Alu-Alu blister packaging to provide a total moisture barrier, ensuring a 36-month shelf life.

• The “Orange Effect” (Technical Transparency): As a pharmacist, your digital product literature should note that Rifampicin causes a harmless orange-red discoloration of urine, sweat, and tears. Including this detail in your B2B dossiers builds trust and professional recognition.

• Bioavailability (BA) Challenges: Achieving bioequivalence for Rifampicin in a combination tablet is technically demanding. Our Mumbai facility utilizes precise particle size distribution to ensure your export version matches the absorption rate of the innovator product.

• NGO & Government Tenders: This combination is a staple for the Global Fund and Stop TB Partnership. We provide full CTD/eCTD Dossiers to help your firm bid for these large-scale international contracts.