Schedule H is a class of prescription drugs in India appearing as an appendix to the Drugs and Cosmetics Rules, 1945 introduced in 1945. These are drugs which cannot be purchased over the counter without the prescription of a qualified manufacture and sale of all drugs are covered under the Drugs and Cosmetics Act and Rules. It is revised at times based on the advice of the Drugs Technical Advisory Board , part of the Central Drugs Standard Control Organization  in the Ministry of Health and Family Welfare . The most recent schedule H (2006) lists 536 drugs from abacavir to zuclopenthixol . 
It should not be used concomitantly with medications known to prolong the QTc interval (. 5-HT3 antagonists , tricyclic antidepressants , citalopram , etc.) as this may lead to an increased risk of QTc interval prolongation.   Neither should it be given concurrently with lithium (medication) as it may increase the risk of lithium toxicity and neuroleptic malignant syndrome .    It should not be given concurrently with other antipsychotics due to the potential for this to increase the risk of side effects, especially neurological side effects such as neuroleptic malignant syndrome .    It should be avoided in patients on CNS depressants such as opioids, alcohol and barbiturates. 
Other permanent side effects are similar to many other typical antipsychotics, namely extrapyramidal symptoms as a result of dopamine blockade in subcortical areas of the brain. This may result in symptoms similar to those seen in Parkinson's disease and include a restlessness and inability to sit still known as akathisia , a slow tremor and stiffness of the limbs.  Zuclopenthixol is thought to be more sedating than the related flupentixol , though possibly less likely to induce extrapyramidal symptoms than other typical depots.  As with other dopamine antagonists, zuclopenthixol may sometimes elevate prolactin levels; this may occasionally result in amenorrhoea or galactorrhoea in severe cases. Neuroleptic malignant syndrome is a rare but potentially fatal side effect. Any unexpected deterioration in mental state with confusion and muscle stiffness should be seen by a physician.