SP-Pyra 125 Suppositories (Paracetamol BP 125mg)

Indications

• Active tuberculosis
• Pulmonary tuberculosis
• Extrapulmonary tuberculosis

Dosage

Children: For children, the dosage should be determined based on weight and should refer to the BNF for Children for specific dosing recommendations.

Adults: The usual adult dosage for the treatment of tuberculosis is 25 mg/kg once daily, not to exceed 2 g per day, as part of a multi-drug regimen.

Mechanism of action

Pyrazinamide is converted to its active form, pyrazinoic acid, in the acidic environment of macrophages. The active compound disrupts the mycobacterial cell membrane metabolism and transport functions, leading to cell death. It is particularly effective against dormant or semi-dormant forms of Mycobacterium tuberculosis, which are not susceptible to many other antitubercular agents.

Pharmacodynamics

Pyrazinamide exhibits its action by inhibiting the synthesis of fatty acids in the mycobacterial cell wall, effectively disrupting the bacterium's ability to maintain its cell structure. This results in the bactericidal effect against Mycobacterium tuberculosis, especially in acidic environments such as those found in lesions of tuberculosis. The drug is more active at lower pH levels, which is significant since many tuberculosis infections occur in acidic conditions.

Pharmacokinetics

Pyrazinamide is well absorbed from the gastrointestinal tract, with peak plasma concentrations occurring approximately 1-2 hours after oral administration. It is widely distributed throughout body tissues, including the lungs, and penetrates well into caseous lung tissue. The drug undergoes hepatic metabolism and is excreted primarily through the kidneys. The half-life of pyrazinamide is approximately 9-10 hours, which allows for once-daily dosing in most treatment regimens.

Interactions

• allopurinol+pyrazinamide: Unknown (increases risk of hyperuricaemia)

Pregnancy

Refer to relevant clinical guidelines, as safety during pregnancy is not well established.

Breast-feeding

Refer to relevant clinical guidelines, as safety during breastfeeding is not well established.

Storage

Store in a cool, dry place, away from direct sunlight.

Mechanism of action

Mepyramine is a histamine H1 receptor inverse agonist. It binds to a G protein-coupled form of the receptor and promotes a G protein-coupled inactive state of the H1 receptor that interferes with the Gq/11-mediated signaling. Mepyramine competes with histamine for binding at H₁-receptor sites on the effector cell surface, resulting in suppression of histaminic edema, flare, and pruritus. The sedative properties of Mepyramine occur at the subcortical level of the CNS. Antihistamines used in the treatment of allergy act by competing with histamine for H1-receptor sites on effector cells. They thereby prevent, but do not reverse, responses mediated by histamine alone. Antihistamines antagonize, in varying degrees, most of the pharmacological effects of histamine, including urticaria and pruritus. Also, the anticholinergic actions of most antihistamines provide a drying effect on the nasal mucosa. /Antihistamines/ H1 antagonists inhibit most responses of smooth muscle to histamine. Antagonism of the constrictor action of histamine on respiratory smooth muscle is easily shown in vivo and in vitro. /Histamine Antagonists: H1 Antagonists/ H1 antagonists strongly block the action of histamine that results in increased permeability and formation of edema and wheal. /Histamine Antagonists: H1 Antagonists/ Some H1 antagonists possess local anesthetic activity ... . /Histamine Antagonists: H1 Antagonists/ For more Mechanism of Action (Complete) data for PYRILAMINE (6 total), please visit the HSDB record page.