Darvocet is a brand-name drug approved by the FDA in 1972 and manufactured by Eli Lilly & Co. Darvocet is intended for the management of mild to moderate acute pain. The original Darvocet was based on two active ingredients: propoxyphene HCL and acetaminophen, according to Chemie.de. However, for safety reasons, another formulation was offered that contained propoxyphene napsylate and acetaminophen, and renamed Darvocet-N. According to RxList.com, there are two strengths of Darvocet-N: the 50s, which contains 50 mg of propoxyphene napsylate and 325 mg of acetaminophen per tablet; and the 100s, which contains 100 mg of propoxyphene napsylate and 650 mg of acetaminophen per tablet. In addition to the two active ingredients, Darvocet-N also has many non-medicinal ingredients.
Propoxyphene Napsylate
According to Medications.com, propoxyphene is structurally related to methadone, and acts as a narcotic and analgesic by interaction with opioid receptors. Although less selective than morphine, the napsylate salt allows better dosage formulation than the HCL salt.
Acetaminophen
Acetaminophen is an acetanilide with analgesic and antipyretic properties. Acetaminophen works by inhibition of prostaglandin synthesis in the central nervous system, which results in elevation of the pain threshold and lowering of the body temperature, according to Medications.com. Acetaminophen is a mildly potent pain reliever and a fever reducer that’s meant to increase the analgesic effects of propoxyphene.
Binders and Fillers
According to Daily Med, Darvocet-N contains four non-medicinal ingredients that can be categorized as binders, including microcrystalline cellulose, hypromellose, pregelatinized corn starch and anhydrous lactose. Binders act to hold the ingredients together, such that the tablets can be formed with the appropriate mechanical force. The corn starch also acts as a disintegrant, which according to Chemie.de, expands and dissolves when wet, facilitating the tablet to disintegrate in the gut and release the active ingredients for absorption. The cellulose derivatives and anhydrous lactose also act as inert fillers, which increase the size of the tablet, making it convenient for production and handling.
Dispersing Agents
According to Drugs.com, Darvocet-N also contains povidone and crospovidone, which act as fillers and dispersing agents for the two active ingredients. Chemie.de notes that povidone is readily soluble in water, and is used as a dispersing and emulsifying agent in medicinal tablets.
Mixing Agents and Lubricants
Magnesium stearate and stearic acid powder are other ingredients in Darvocet-N, and both act as lubricants and stabilizers in the compounding process of drug manufacturing. Stearic acid combines with another ingredient, polyethylene glycol, and helps to mix the ingredients homogeneously, according to Chemie.de. Purified water can also be considered a mixing agent, while talc powder and silicon dioxide are also added for lubrication. Lubricants improve how the drug ingredients move through the production-line, and help prevent them from sticking to equipment.
Preservative
The main preservative used in Darvocet-N tablets is sodium citrate. According to Chemie.de, sodium citrate retards spoilage through antioxidant behavior, which can kill molds, yeasts and some bacteria.
Coloring Agents and Coatings
According to Daily Med, Darvocet tablets contain FD&C Red #40 and FD&C Yellow #6 dyes. Titanium dioxide is another ingredient added for coloring because of its ability to provide whiteness and opacity to medical tablets. Methacrylic acid-divinyl benzene copolymer is added as an exterior hardener, and carnauba wax as an external covering.
