Table 2.
Pharmacology of chloroquine and hydroxychloroquine.
| Parameter | Chloroquine | Hydroxychloroquine |
|---|---|---|
| Discovery year | 1934 | 1946 |
| Basic compound | 4-aminoquinoline | 4-aminoquinoline |
| Drug class | Anti-malarial | Anti-malarial |
| Drug formula | C18H26ClNO3 | C18H26ClNO3O |
| Molecular weight | 320 g/mol | 336 g/mol |
| Chemical nature | Weak base | Weak base |
| Salt for therapeutics | Phosphate | Sulfate |
| Availability | 250 mg (150 mg base); 500 mg (300 mg base) |
200 mg (155 mg base) |
| Brand name | Aralen (US) | Plaquenil (US) |
| Absorption | Upper intestinal tract; 2–4 hr; 89%; not affected by food |
Upper intestinal tract; 2–4 hr; 74%; not affected by food |
| Bioavailability | 0.7–0.8 | 0.7–0.8 |
| Distribution | Large: 60 000 L | Large: 47 257 L |
| Terminal half-life | 45 ± 15 d | 41 ± 11 d |
| Residence time | ≈ 900 h | ≈ 1300 h |
| Metabolism | Unmetabolized 62%; rest is dealkylated in liver; enzyme cytochrome 450; active metabolite desethylchloroquine 39% |
Unmetabolized 58%; rest is dealkylated in liver; enzyme cytochrome 450; active metabolites desethylchloroquine (18%) and desethylhydroxychloroquine (16%) |
| Clearance | Kidney (51%) and liver | Kidney (21%) and liver |
| Toxicity | ||
| Animal | 2–3 times more toxic than chloroquine (albino rats) | Safer |
| Cardiac | Same | Same |
| Ophthalmic | More (≈ 20% in 5–7 years) | Less (≈ 1% in 5–7 years) |
| Drug-drug interaction | Same | Same |
| Pregnancy and lactation | Safe | Safe |
| Indication | ||
| Malaria treatment | Yes | Yes |
| Malaria prophylaxis | Yes | Yes |
| Rheumatology | Not recommended | Drug of choice |
| Status for COVID-19 | ||
| In vitro antiviral activity | Less potent in vitro | Hydroxychloroquine is more potent in vitro than chloroquine |
| Treatment | Used in studies | Used in studies |
| Prophylaxis | - | Yes (ICMR) |