Hydroxyquinolines, primarily represented by Clioquinol (Iodochlorhydroxyquin), are synthetic antimicrobial and antiprotozoal agents. In the Indian context, they are most commonly used as an intestinal amoebicide and for the management of certain dermatological conditions. Their mechanism involves chelation of ferric ions essential for microbial enzyme function, leading to inhibition of DNA replication and cellular respiration in susceptible pathogens. While their systemic use has declined globally due to neurotoxicity concerns (SMON syndrome), topical and limited oral use persists in India for specific indications under strict medical supervision.
Adult: Intestinal infections: 300-600 mg orally three times daily for 7-10 days. Maximum: 1.8 g/day. Topical: Apply a thin layer to affected area 2-3 times daily.
Note: Oral: Take with or after food to minimize GI upset and improve luminal action. Do not crush or chew; swallow whole with a full glass of water. Topical: Clean and dry the affected area before application. Wash hands before and after use. Avoid contact with eyes, mouth, and mucous membranes.
The primary mechanism is chelation of polyvalent metal cations (especially ferric Fe3+ ions) that are essential cofactors for several microbial enzymes, including those involved in the electron transport chain and DNA synthesis. This chelation disrupts critical metabolic pathways in susceptible protozoa (e.g., Entamoeba histolytica trophozoites) and bacteria/fungi. It also exhibits direct cytotoxic effects on trophozoites.
Pregnancy: Category C (US FDA). Animal studies show toxicity. No adequate human studies. Use only if clearly needed and potential benefit outweighs risk, especially considering neurotoxicity potential. Avoid in first trimester.
Driving: May cause dizziness or visual disturbances. Patients should be cautioned about driving or operating machinery if they experience these effects.
| Thyroid Hormones (Levothyroxine) | Hydroxyquinoline's iodine content may alter thyroid hormone requirements and interfere with thyroid function tests. | Moderate |
| Lithium | The iodine load may potentially exacerbate or induce hypothyroidism, affecting lithium kinetics and toxicity. | Moderate |
| Other Neurotoxic Drugs (e.g., Isoniazid, Metronidazole, Chemotherapy) | Increased risk of additive neurotoxicity (peripheral/optic neuropathy). | High |
| Antacids, Calcium, Iron, Zinc Supplements | May chelate these cations in the GI tract, reducing absorption of both the supplement and the drug's efficacy. | Moderate |
Same composition (Hydroxyquinolines (300mg)), different brands: