Cetirizine is more toxic than Bisoprolol according to hodge and sterner scale, and yet Cetirizine is available as OTC drug, and Bisoprolol is a prescription drug! Any insights?
These drugs are for completely different indications. Cetirizine (marketed as Zyrtec, for example) is for allergy. Bisoprolol is for high blood pressure and serious heart problems. The level of safety expected for the proper dose of an OTC drug for a non-life-threatening indication like allergy is high.
The Hodge and Sterner scale relates to the LD50, the acute dose required to kill 50% of a set of study animals. Presumably, the normal dose of cetirizine is very far below the LD50. The oral LD50 in male rats for cetirizine is 703 mg/kg. If it is the same in humans, the LD50 dose would be 49 grams for a 70 kg person. The dose of Zyrtec is 10 mg/day. Although cetirizine certainly can have side effects at the intended dose, it is very unlikely to kill anyone at a dose 1/4900 of the LD50. Here is the list of side effects: https://www.drugs.com/sfx/zyrtec-side-effects.html. They do not appear to be life-threatening. For a drug with side effects likely to be minor when used as directed, and that is used to treat a condition that is not generally life-threatening, it seems reasonable to be available over-the-counter.
By the way, the oral LD50 of bisoprolol in rats is 940 mg/kg, about the same as cetirizine, yet the maximum daily dose is only 20 mg. Overdose can lead to serious problems. Here is the list of side effects:
https://www.drugs.com/sfx/bisoprolol-side-effects.html. They can be pretty bad, which is presumably why this drug is not OTC.
Yeah Dr.Adam understandable, but doesn't the classification matter? I mean doesn't being classified as moderately toxic and slightly toxic matter with regard to use? I know both drugs are used at a dose that is far to induce death, but I was wondering what use or insight will I gain if I know this as being slightly toxic or moderately toxic?
And also the maximum dose for cetirizine is 10 mg /day. Does this relate to just efficacy(increasing the dose won't result in more benefit), or it can be that exceeding 10 mg /day will result in some form of toxicity?
I don't think there is much use in knowing the LD50 when it comes to therapeutic dose. The therapeutic dose is determined experimentally. It must be demonstrably efficacious in clinical trials. If there are any side effects at the therapeutic dose, then their severity must be commensurate with the use of the drug. Serious side effects at the therapeutic dose will not be acceptable for a drug that is used chronically to treat non-life-threatening conditions, unless perhaps the side effects are extremely rare (acetominophen/paracetamol is a case in point). Because the risk of side effects usually increases with the dose, the recommended dose is not going to be any higher than necessary to achieve the therapeutic effect. In many cases, several dosages are available and can be selected based on the needs or physical state of the patient. For example, a patient with reduced kidney function might be given a lower dose of a drug that is cleared by the kidneys than would be a person with normal kidney function. Or, someone with severely high LDL cholesterol might be given the highest permitted dose of a statin, with the understanding that the increased risk of side effects is offset by the need to reduce the risk of atherosclerosis.
Thanks Dr.Adam. Although off topic, but why would someone risk diabetes by taking statin as demonstrated by SPC (As common adverse reaction and suspected causality is there ) for a minimal benefit (I hope I have read this right, Statin is promoted to decrease the risk, but public weren't informed that this is the relative risk, not the absolute risk)? Aren't risks here outweigh the benefits? And I do agree that there are some populations that might benefit from statins but I think they are few (Where benefits outweigh the risks)
I'm not an expert on statins. For a believable source of information, I looked here, the Mayo Clinic:
https://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/in-depth/statin-side-effects/art-20046013
The risk of increased blood sugar due to treatment is described as "small but important enough that the Food and Drug Administration (FDA) has issued a warning on statin labels regarding blood glucose levels and diabetes. Statins prevent heart attacks in patients with diabetes, so the relevance of the mild increase in sugar values with statins observed in some patients is unclear. The benefit of taking statins likely outweighs the small risk to have the blood sugar level go up."
As with all prescription drugs, one must balance the benefits and risks. No doubt there is active research on this particular subject, since there are so many patients on these drugs.
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