Dal polythiol al dmps

La Dow Chemical aveva trattato i chicchi che la popolazione iraquena mangiò (soprattutto i kurdi...) e alla stessa venne richiesto di fornire un antidoto. Fu così che nacque la resina "polythiol", un composto chimico a base di mercapto destrano. Agli iraqueni venne anche somministrato il dimecaprolo "BAL" (acronimo di anti-arsenico britannico), che si rivelò poco efficace per chelare mercurio.

Da qui nacquero studi che misero a confronto la "resina Dow" con due tipi di penicillamine e con il DMPS, dimostrando la maggiore efficacia di quest'ultimo.

In sostanza gli iraqueni fecero da cavie per tutti quelli che seguirono, me compresa.

All'indirizzo http://www.hgtech.com/HSE/Medical%20Treatment.html ho copiato la tabella che segue, piuttosto accademica. Al posto del DMPS c'è il DMSA, ma la sostanza mi pare identica. 

Una curiosità: i chicchi trattati e finiti "casualmente" nell'alimentazione di questa povera gente, avevano colore rosa. Leggo che inizialmente lo presero per un modo del governo di trarli in inganno, poi, non potendo decifrare gli avvertimenti in inglese e spagnolo nè il simbolo di pericolo privo di significato per loro, si decisero a mangiarli. Io ho fatto per anni un po' di orto nelle mie case e mi sono immediatamente ricordata di una confezione di piselli, super-resistenti a qualunque cosa, di colore... rosa! Il mercurio ha evidentemente accompagnato fedelmente tutta la mia vita, insidiandomi insospettatamente con i modi più diversi!

Drug Name	BAL (British Anti-Lewisite) - BAL is used only in acute ingestion. BAL(dimercaprol in an oil solution) is contraindicated for use in organic (methylmercury) toxicity because it can raise levels in the brain causing further neurotoxicity.
Adult Dose	3-5 mg/kg/dose deep IM injection q4h the first 2 d; followed by 2.5-3 mg/kg/dose IM q6h for 2 d; then 2.5-3 mg/kg/dose IM q12h for 1 wk
Pediatric Dose	Administer as in adults
Contraindications	Methylmercury toxicity; G-6-PD deficiency, unless a life-threatening situation exists; Severe peanut allergy, as the excipient for the dimercaprol is peanut oil.
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Caution with patients that are G-6-PD deficient, as it may produce hemolysis. Side effects include abdominal pain, nausea, vomiting, headache, elevated blood pressure, tachycardia, burning sensation to the lips and throat, constricting feeling of the throat, conjunctivitis, blepharospasm, lacrimation, rhinorrhea, salivation, burning sensation to the penis and urticaria (some side effects responsive to diphenhydramine cotherapy).

Drug Name	Penicillamine (Cuprimine , Depen) - PCN (D-penicillamine) forms a complex with mercury and is excreted in the urine; therefore, it should not be used in renal failure. It cannot be considered a first line agent because of the safer and more efficacious agent, dimercaptosuccinic acid.
Adult Dose	15-40 mg/kg/d, up to a maximum of 250-500 mg PO q6h ac (Continue 1 wk until decline in urine mercury levels)
Pediatric Dose	20-30 mg/kg/d PO once or twice daily before meals (ac)
Contraindications	Avoid in patients with penicillin allergy.
Interactions	Antacids, digoxin, iron
Pregnancy	D - Unsafe in pregnancy
Precautions	Side effects include GI disturbances, rash, leukopenia, thrombocytopenia and proteinuria. Use in caution during renal insufficiency. Therapy with d-penicillamine may be dangerous since the main route of elimination of this complex is renal.

Drug Name	DMSA (2,3-dimercaptosuccinic acid, Succimer, Chemet) - DMSA (2,3-dimercaptosuccinic acid) is used in both inorganic and organic mercurials. It is considered superior to PCN. DMSA is an oral medication that has fewer side effects than do PCN and BAL. Because of its ease of use, good efficacy and safety, initiate treatment with this agent if there is good evidence that significant absorption will occur, as mercury levels may not be readily available.
Adult Dose	10 mg/kg PO tid for 5 d, followed by 10 mg/kg PO bid for 14 d
Pediatric Dose	10 mg/kg or 350 mg/m2 PO q8h for 5 d, followed by 10 mg/kg PO bid for 14 d
Contraindications	Hypersensitivity to Succimer
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Side effects include mild GI disturbances and a transient rise in liver enzymes. The product has a strong sulfur smell. Thrombocytosis, eosinophilia, and neutropenia have all been reported with therapeutic use, and all are reported to resolve when therapy ends.